Jesus loves me be because she stalled out in the Monkey section and had only just left the bears, lions and tigers.

Dear all - a Brief history

Although I am lucky enough to have an 89 Vette in Toronto (in absolute cherry condition) I also have a 92 Vette in the UK (where I am now) that I got of e-bay as a non-starter a little over a year ago. With only 40,000 miles she was still in pretty appalling shape (I have since replace the ECM, transmission, Opti-Spark and had tuned by a performance shop whom say the motor is sound - small mercies !) Also have all the replacement interior parts and gonna get a new carpet too)

I seem to be left with 2 issues I hoped I could trouble your guys for your opinions on (cheers)

OVER HEATING

Ferried/Drove to Paris a couple of weeks ago and the car was great the whole way there (maybe 85 degrees Fahrenheit outside) the car coolant temp stayed at a steady 176 degrees Fahrenheit then entire way to the city (approx 3+ hours of highway driving) but when I hit town and was stopping at lights the temp went up AND FAST.

Within about 10 minutes it was showing 230+ on the digital display and was very very close to the red on the analog gauge in the dash. then a strange things happens .....

The digital display begins to drop way down (like from 235 down to 60 degrees Fahrenheit - then up and down) then within 8-10 seconds the car sputters stalls out. (then is tricky to start - cranks for 10 second before she lights back up)

Please Note - I did a basic once over the car before leaving - reserve coolant tank showed full as did the coolant cap in front of the passenger side so I do not believe there is a lack of coolant nor a leak.

When I got back a local garage thought my RAD was the problem and is why only the wind at higher speeds seems capable of keeping the car at a good temperature.

I do hear the RAD Fans kick in as the car warms up but this does not control the temp enough to stop it hitting 230-240 when driving slow in town or in drive through Zoo's as was the case yesterday.

Not easy getting Vette bits out here but will be returning to Canada next week for a couple of months (miss my 89!). Are there any parts/sensors you folks think I should pick up for the 92 when back home ? I can get a RAD there I imagine cheaper than here. Would you suggest I try to service the RAD I have? get an upgrade to the 92's existing RAD fans ?(England is by no means a hot country so I can only imagine what it is like in the southern states etc). Clearly I have a cooling issue of some sort but am not really sure where to start - many thanks for your thoughts (much appreciated)

HIGH IDLE

I know from going to the odd Vette shows that my 92 is not idling the way it should. Seems way high to me - allow me to explain

When started cold the rpm's sit at about 1500-1700 (even after a 5 minute warm-up) when in gear she drops down to a more comfortable 700 rpm.

When started hot (or in neutral when warmed up) the rpm's still sit at 1000 ish - is this something that can be modified via the chip in ECM ? could it be something else ? don't think my idling is right though - any thoughts would be greatly appreciated

warm regards

I'm hardly an expert, and the sudden drops in temperature reading are very strange, so perhaps it could be a sensor. There are a couple - one in the water pump, and another on the passenger side of the block. between #6 and #8. Another thought might be an air bubble in the coolant - it would be worth bleeding the system to see if any air is trapped.

The idle speed is controlled by the PCM, but some other factors might be the idle air controller or the throttle position sensor, or perhaps a vacuum leak.

A couple of things:

The radiator is definitely worth looking at. Years of crud can build up on the surface and it is worth taking out and carefully cleaning the outside of the radiator(not an easy job but worth it). Check that there isnt any junk trapped up between the radiator and the AC heat exchanger.

As far as the temps, I agree that it could be the sensor or bubbles in the coolant. Have you experienced excessive coolant overflowing into the plastic tank? If so, could be as simple as the radiator cap (surge tank cap) not holding enough pressure.

For the erratic idle - possibly a stuck IAC valve or vacuum leak. Spray the engine with MAF or TB cleaner while it is at idle and see if you can prompt any surging.

In terms of parts, I would 'personally' pick up the following:

- Radiator cap
- coolant temperature sensors (both, water pump mount and passenger side head mount)
- IAC valve
- Coolant hoses (have been known to fail / collapse
- Maybe a new accessory belt (1992's are double-sided and hard to get sometimes)
- a new 383 shortblock

Actually, just kidding on the last one :-)

Good luck!

Where in the UK are you?

I think the heat is one issue and the Idle/Stalling is another that may have a relation.

I think your computer is on it's last leg and heat disturbs it to a point of malfunctioning.

It's like the brake Master Cylinder, it is not tied to the cooling system in any way, however, if you have an aging one, Higher under hood temps lead to blow by and you have to pump the brakes.....get out of stop and go traffic....the temps come down and the brakes suddenly work again without needing to be pumped.

That is my theory with your wacky readings and stalling. But I have no clue if you care for the truth. I'm just throwing things out there.

Second, thepartsladi has a direct replacement radiator for $100USD. You should pull yours, have it "boiled" out at a radiator shop or get a replacement...years of sediment is in the bottom of the "inside" of the radiator, if you've never pulled it for cleaning, that is your issue.

Yes, there will be debris in between the A/C condenser and the radiator. Once you pull the top shroud off the radiator to remove it....you'll see what everyone is talking about without a doubt. That Debris needs to be addressed at least annually.

The gauge and temp bouncing around like that indicate possible air in the system. It is easy and free to rebleed it for trapped air. I would run it up to operating temp so the thermostat is open and then rebleed it.

On the passenger side there is an opening in the radiator shroud where you could use a flashlight and peer in there to see if there is any debris in front of the radiator.

Factory setting is for the main fan to come on at 227*F, or when the AC is turned on. I think your 92 is like my 95 and the secondary fan comes on at 236*F. The fans are controlled by the ECM, which in turn gets it's temperature inputs from the coolant sensor on the waterpump. The sensor on the right head only feeds the analog gauge.

The erratic idle could be a vacuum leak, IAC, or other things as mentioned by others. Perhaps (only a perhaps) a throttle body cleaning would help (again it is an inexpensive option).

Temps: 176 is low for normal highway operation on a 92. Do you know what thermostat's in there? However the eratic gauge readings before you stalled indicate there may be another problem. The 230-240 at the zoo, yep, normal for a 92.

A normal 92 with a well mintained cooling system will run 192-194 all day on the highway even at 100 degrees ambient.
Temps rising to 230 at a stop within 5 minutes are normal and the fan(s) won't start to kick in until 235.
You can manually control one of the fans without affecting their normal operation by installing a $2 switch.

I'll bet you don't need a radiator. Before you do anything, when was the cooling system last flushed? A good flush includes pulling the knock sensors on either side of the block (easy but messy to do). Check for garbage BETWEEN the radiator and a/c condensor, you need to shine a flashlite thru on of the small holes in the fanshroud to see in there, you can't tell by looking from the front of the car.
Have the radiator cap tested. Check all the hoses, on a 92,if they're origional, they will need to be replaced soon, I know, I own a 92. The 92 also has 2 air bleeds, one on the throttle body and one on the thermostat housing. These should be cracked open when refilling the system ( use a screwdriver to open them, do not use a wrench on the nut). Close them, warm up the engine past 180 and creck them open again, look for a soild stream with no spitting of air. I'd stuff a few rags under them to prevent coolant from running on to the opti.
Don't buy a rad, don't upgrade the fans. Do buy the hoses, possibily a cap (cheap), check between the rad & a/c cond. and do a good flush. This will return your 92 to normal temps. If you want to install a manual switch, let me know.
I don't even turn on the manual on mine until 215-220.

The hi temp shut down and erratic gauge reading is electrical and will be harder to diagnois unless it happens again. You should check or any codes and clear them. This is easy and is explained in the tech section here.
92's are noted for having ground problems. The ground wires should be looked at and the connections to the frame should be cleaned and sealed.

The idle does sound high.
You can check for vacuum leaks but if you have one, you'll usually get a rough idle.
It's probably the IAC valve. These can be cleaned but there's only a 50/50 chance he cleaning will help. AND most guys make the mistake of moving the valve pintal when cleaning them which you are not supposed to do.

thanx pianoguy djxib, jhammons01, 95vette, billh

Andy - I'm in a city called Milton Keynes (about 45 mins north of london) and thanks for the list bits - good ideas

Also sounds like BillH's approach would be cost effective - spent so much on this old girl already (but never want to cut any corners). Also I would very much like to know how I might go about installing a fan switch for instant peace of mind.

Guys thanks for the great step by steps - the shop here that will be doing the RAD work upon my return in a couple of months will not have worked on a vette before so I will print off your insights for them to read first. Many thanks

Is there a rad-maintenance document any of you are aware of (ie things linke how to bleed, flush and maintain etc) I might take a crack at bleeding it myself

Could I ask what temp you guys would think is alarmingly high? like pull over now high ?

Also if the cooling is working right on a 92 vette and you are driving in at most 75 degree weather - what should the engine temp reach in traffic?

Sounds like 240 degrees is not that high - but it is about here the engine consistantly stalls out .... my restoration continues .... and loving every minute of it !!

Just wish there were more folks whom can work on them over here (did not realise how fortunate I am in Canada)

thanks again for all your time

Does you car have two fans?

Mine does, and when it's really hot out it needs both to keep it cool.

When the fan motors go, they'll be intermediate, work sometimes and not the other. so that may be what your seeing.

240 is a little high....shut it down at 250°

I just had a coolant temp sensor go bad on my '89. There is 1 for the computer and another one for the gauge. The gauge one was working fine. The car would start right up, but idled higher than normal. Would eventually stall out, then it was very hard to get restarted. What was going on is that the sensor that feeds the computer was telling the computer it was like -15 degrees out, so it was dumping tons of fuel into the car and idling high like it was trying to warm up. Never got a code thrown because -15 degrees is possible I guess.

I have datalogging stuff so I hooked the car up to datalog to find out it was saying -15. But again, the dash gauge read just fine. The sensor is the one in the intake, and it cost $13 at Advance Auto.

It could also just be debris between the radiator and condenser as mentioned before. Get that cleaned out first.

The if the coolant temp sensor isn't bad and causing both your problems, then I'm betting you have a sticking or non-working IAC valve causing the idle rpm issue. Easiest way to check (as long as your AC works): warm your car up good, have it sitting idling in gear, turn the AC on. Idle should dip down, then recover back to at least where it was, maybe a hair higher. If the idle drops down a couple or few hundred rpms and does not recover or if the car stalls out, the IAC valve is either sticking or needs replaced.

I took control of my fans some years ago, I wired to the dash and they turn-on when I want them too. I have now also done that with my electric water pump. This will definitely help.... or at least it helped me.

good luck !

Quote:

I'll post the manual fan switch w/pics soon.
I'll post the flush also along w/pis of the 2 bleeders. Bleeding is a cakewalk.

Alarmingly high on the highway 240. If you turn on the a/c, it will activate the fans to get you home.

75 degree weather - please reread my first post.

Turning on one fan at a redlight will drop a 215 reading to under 200 in a couple of minutes.

Good post Dan.

Beach and Bill, Stop it.....Why would you suggest that this guy modify a system that has not been properly maintained??

The Car is how old?? I'll betcha a smooth $100 that the radiator has NEVER been pulled and boiled. Go back and read the shape the car was in when the OP received it from the Previous owner before you take my bet. I'll remind you....The car was neglected so badly that even at 40k miles....it wouldn't even start and run.....

Pet peeve for me...."modify prior to maintaining", when the Mods don't work go back and check the things you should have in the first place........Does that sound correct in any way?

An 18 yr old car with only 40K on it and in that condition has probably been sitting awhile. The radiator is probably half blocked up inside and out. Check for corrosion and deposits in the radiator. And maybe a few plastic bags and leaves in front of the radiator. Depending on the condition, you might be better off replacing it. I would also flush the coolant passages in the engine block out thoroughly with a pressurized hose. That chemical crap you buy in bottle isn't enough for a block with a thick layer of corrosion and slime.

The temp sensor should not be dropping to 60F, even with an air bubble. That air bubble is still pretty damn hot from the hot water and steam surrounding it and conduction from the metal. I would try to duplicate that condition and check the resistance of the temp sensor and compare with the factory specs and possibly replace it.

Don't the LT1s have two different temp sensors that can be read on the dash? Why not compare these?

Quote:

Assuming the car has any heat transfer ability to begin with. He said his fan(s) were already running, so I'm not sure what that'd solve.

Quote:

So what part of this didn't you understand?

"Before you do anything, when was the cooling system last flushed? A good flush includes pulling the knock sensors on either side of the block (easy but messy to do). Check for garbage BETWEEN the radiator and a/c condensor, you need to shine a flashlite thru on of the small holes in the fanshroud to see in there, you can't tell by looking from the front of the car.
Have the radiator cap tested. Check all the hoses,"

Sounds like maintainence to me.
Maybe the "Before you do anything" part confused you.

John's easily confused. That's why his shoes have velcro straps.

Quote:

Yes, the sensor on the w/p is the one that goes thru the ECM and could be a part of the idle/shutdown problem. The other sensor on the right bank only works the gauge, doesn't go thru the ECM.
You could compare the two. But both could be off.
I know my gage sensor is off, reads very high. I just haven't changed the sensor, don't really care because I use the digital and checked the against an ASTM thermometer in the reservior. It was within 5 degrees,could be accounted for by the difference in temps between the w/p & reservior, but that's close enough for me.

The gage sensor spec is 1400 ohms = 100 degrees

As far as I can see, there isn't a spec on the w/p sender.

Quote:

Could be.
It's also possible a correctly done flush will return things to normal.
My 92 had 60k on it when I got it. It sat a lot, only 5,000 miles were put on it in 6 years. No records of it ever being flushed but a w/p installed at 40k.
I did 3 flushes at one time: drained, filled with straight water, drove 10mi, drained, filled with a bottle of the crap, drove about 20mi, drained, filled with water, drained & filled with distilled & antif.
An amasing amount of crap came out the first 2 times, not much on the last.
That was 3 years ago, the coolant's only slightly cloudy now. It's time to do it again this fall.

Absoutely no cooling problems since, so I didn't need to boil the rad or replace it.

Quote:

What's wrong with velcro straps?

All the suggestions above seem correct to me.

#1 I would clean the debris from between the radiator and condenser.

#2 I would flush the system well and refill properly. While doing this, check the hoses, thermostat, cap, etc.

#3 I would check/test/replace the sensor.

#4 I don't think the fan switch is "necessary" but a lot of guys do it. My car has an automatic switch to turn the aux fan on at 205*, the PO installed it. Works fine for me.

Matthew

Quote:


Ummmmm....Uhhhhh....I think not.

billh, I only focused on the "manual switch" comment. Why are we going there just yet??

Lee Majors walks in to the Doctor complaining about a hang nail...next thing you know Billh is the doctor and Lee Majors is the 6 million dollar man. Sure it's cool to run 60mph but couldn't we get a hand creme to address the Hang Nail??

Yes, the Velcro shoes helps on days when my dyslexia is acting up CC. What confuses me the most is when people have this nifty computer to monitor these things, and they bypass that computer for system that has the human occupant watching a readout and flipping manual switches while driving in traffic....but only do this on Hot days.

dan0617, Like I finished with, I am not sure of that statement, so thanks for letting us know that this could not be an issue.

Quote:

Oh? What you said: "Why would you suggest that this guy modify a system that's not been properly maintained."

What I said: "Before you do anything, do the proper maintainence"

It's also interesting that you think his nifty little computer is malfunctioning and that the computer's not tied into the cooling system.

Moe, Have your mechanic pull any codes. It's best to do them directly on the car's dash.
See if there's a code 14 or 15 in module 4.1.
14 & 15 are hi and low readings from the temp sensor in the waterpump. This goes back to what Dan mentioned about the ECM getting a faulty reading on water temp.

Quote:Quote:Quote:Quote:Quote:Quote:
you can be mad at me all you would like. There are plenty of things that you have much more knowledge about than I do. It is clear that you do a ton more work on these cars than I have/will.

All I'm calling to question is, why do we so quickly advise someone to make modifications, in the primary stages of the first sign of troubles....we get all the things fixed and there are still troubles.....go for the mods....

It's alright if you dislike me from this point forward.....this isn't the first time nor the last time I have destroyed a well valued belief for others.

Quote:

Yes, do pull the codes, but for some reason mine didn't throw a code. I think it was because mine was still sending some voltage, but not much. It showed like -15 degrees when I datalogged, which I guess the computer sees as a possibility. If it doesn't send any voltage then it would read -40 in the datalog, and I'm guessing then a code would be thrown.

If you happen to know anyone with a USB to ALDL cable you can borrow, borrow it, then download Tunerpro RT for free and use it for datalogging. It's fairly easy and free and by looking at what is being logged you could likely tell your problem.

But still, clean the junk out from in front of the radiator first.

Quote:

Yea, unfortunately both those codes aren't the greatest since most of the diagnosis for a LT1 is attaching the Tech 1 to take a temp reading. The codes could also indicate a short/open in the wiring. At least the code chart has the ohm values for the sensor. The ECM sends 5v. to the sensor and the voltage does change with resistance. I think if the ohm reading was off at all, I'd change the sensor.

Moe, Here's the location of the 2 cooling system air bleeds on a 92. When opening these, just use a screwdriver on the round knob, do not put a wrench on the hex part. Open 1/2 turn. The best way is to crack these open before you install new coolant. Then shut them lightly before engine start.
Then warm up the engine to where the thermostat opens and crack each open. If there's a steady stream and no air spitting, you're done. They only have to be open a couple of second to tell this. Do not over tighten these, they're brass.

This is only a small part of a proper cooling system flush.

You can try it now but I agree with CC that air in your system is not why you have the current problem.

Attach file:

---

  IMGP0546.jpg (0.00 KB)

Manual Fan Switch.

Moe, Here's where to put in a manual switch. Note that there are other options like the automatic switch Matthew mentioned that installs in the block, about $40. There's even a programable setup that reads temps with a probe in the radiator and is adjustable to any temp you want, $100.

Peace of Mind is a good way to describe taking control of the fans. I put mine in because I didn't like with the temps that the GM engineer set. I actually rarely use it and if I hit 220 at a redlight, I know it will cool down after I get going. I really only use it in a long traffic jam.
You do need to preform the maintainence on your system and get it back to normal before installing this.

Any 12v. rated single throw (on/off)toggle switch will work.
The switch only grounds the fan relay and does not see the high current that the relay sends to the fan. So, an inexpensive switch and 16 gage wire are all you need.
Mine's wired into the secondary fan relay (which turns the pass. side fan only). The relay is the one shown in the pic, driver's side on the rad shroud. You need to make a connection to the dark blue/white wire in the relay harness.
DO NOT cut the wire, just splice into it. This way you retain all the computer controled functions.
Run the 16 gage wire from that splice to one pole of the toggle switch and run s wire from the other pole of the toggle switch to a chassis ground under the dash.
That's all there is to it.

Attach file:

---

  IMGP0548.jpg (0.00 KB)

240 is normal for sitting in long stop and go traffic and outside air temperature 90+ degrees?

Girls ... girls ... girls - lets all play nice ! Gosh I leave you all alone for a weekend and it's a slumber party gone mad by the time I am back !!

Guys thanks again so much for your great insights - also BillH and jhammons01 - thanks for the great images and laughs - not that I think it will matter to you lot but I think you are all right. Indeed the car has low miles but she was not looked after (shipped in to UK from Japan) sun damage to interior (light grey on light grey) has turned a lot of the plastics brittle - and she was used as a dogs limousine - they dog hair I have vacuumed out of the back was hideous. Have all the replacement trim ready to go in and plan to get a new carpet too.

The electronics was a similar story (the ECM looked like it had touched the sun - one of the 4 plugs melted into the socket) all was replaced. I got her going (and trouble shot/resolved many sub-issues)- keep feelin my list is getting shorter - and it slowly is. Only really my overheating and high idle left. I believe I have resolved the random speed display at stand-still (when I am stopped the digital display shows random speeds - 20 to 200 mph - the really crappy thing is it roll's miles on my tachometer when I stop for a train/at lights etc) the shop here has a sensor on order - I printed your notes on this subject for them to read first - they believe they have it cracked - part should be here tomorrow - hope so cause I fly back to Canada on Wednesday)

Comparing the Digital Dash coolant temperature to the analog temp gauge also on the dash

I watch these like a hawk - they seem to be in sync - kinda tough to read the analog gage though - when running what I believe is HOT the needle is just inside the last section of the gauge (the section which is 20% red indicating the red line) maybe a third of a inch out of the red - the Digital dash at this point shows about 240+ (think 243 is the highest ever seen). But it is here where the analog does not move but the digital dash gage drops down to 140 ish - then 170 - then 130 etc and about 10 second later she stalls out and it is tricky(ish) to restart - continues to stall out if used

LOL - I was in the middle of Paris when this was 1st happening - hot day out - stalled maybe 3 times getting to the hotel - to boot I ran out of gas cause I was looking at the temp gauges so much - my girl was not impressed - nor was she when I beat the crap out of two frenchmen later that night (after a lovely diner and wearing a suit) - nor was she still the next day when I opened up the Vette on the french highways to get the ^*&%*# out of France - got her up to 240+ kmh - was only a 2 lane highway so had to ease off (I had my video camera in one hand and the wheel in the other - again she was not impressed !! got some great footage though)

Got to the ferries in Calais and the jon-darm (coppers) stepped out in front and waved me over (my girl was like "your gonna get done for speeding" and I said back "no I'm gonna get done for GBH (grievous bodily harm) for those 2 french pricks I hammered last night - so I handed her all the money passports etc - said to get a room in Calais and when I'm out we'll talk about you taking me back - she laughed - first time all weekend. Amazingly enough I did get a speeding ticket but it was for 9 kmh over (and not the 140kmh I was actually doing) good job he did not watch my camera. The priceless moment was I had to sign for my speeding ticked but my right hand was a swollen mess (broke 2 knuckles and the bruising went past my wrist - really was an ugly scrap and there was 2 of em - then just 1 and then funnily enough none at all - the whole time this little dance was occurring my girl was in the bathroom - when she came back I was just finishing - again she was not a happy chappy ! But when I signed for the ticket the copper saw my hand and of course asked what had happened (could not hide it - sign and fight with my right) so I says to him " well I do live in England and you know what the English are like ....." he smiled and said "I do" - good to have a Canadian accent versus English ANYWHERE outside the UK over here - they all see the Brits as the mad dogs of Europe - they are not wrong - they are nuts over here !!

The Corvette shop out here in England (2.5 hours drive away) said there were no codes 2 months ago - also the shop working on her now (45 mins away) says there are no codes - I am not sure if this was done through the dash display - believe they both used an external device to establish this

Also the limited check of the over-heating (so far) have been a visual inspection for debris etc and he also put his hand on the rad when hot - he said only the centre felt cool - figured the RAD was not working as it should.

There is another shop whom will take the RAD out and flush it - I assume also the block (thanks again all for your notes on this - will ensure things are done to your spec) but if a new rad is only a 100$ back home - may consider getting it (plus new hoses etc) and she is 17 years old now. Are there complete sets of hoses sold ? Don't mind tracking them individually though

I am so very lucky to have a mint 89 back in Toronto - dreamt about her last night - just put new Goodyears all round ...... its gonna be a good summer (well what's left of it - weather in England is always a bit wet !!!)

thanks again all

For future reference, with a 16psi you can run the coolant up to 265F before you risk boiling over a 50/50 mix of water and antifreeze.

I'm not saying you should be anywhere near that during normal driving, but if you're out testing it, there's no need to shut it down at 240F, you can still nurse it home.

If it boils into the expansion tank after you shut the car off, that's normal for hot coolant and doesn't mean the car is boiling over. The coolant is hot and as soon as it expands past the cap it is at atmospheric pressure and will boil.

Quote:
Thanks for keeping it "light" in here

BillH, I apologize and promise to keep my mouth shut when the Demons are trying to slip out....

** note to the French - do not mess with Moe_Vette ;-) **

No problem, John.

Quote:

Pics of:
1) girlfrend
2) beat up frenchmen

or it's all bs.

Matthew

Dear all and Mat

Funny thing - in the good 14 seconds it took to lay em both out I only had time to grab my girl and leg it (no bs) Plus I remember every glorious second in digital red matter (between my ears)

I do have a picture of me and my girl though (been with her for 25 years - since we were both 16 years old). Dad always taught me there is only one thing you fight for and that's your girls (wives, sisters, mums, daughters and always your girlfriend). Not that I always followed this religiously but I sure do these days and believe me they had it comin - nobody disrespect's my girls ...... nobody !!!

Glad my idle banter was able to lighten things up a bit (you guys are all really great and your help out here in the UK is very much appreciated) - do you guys every all get together for a beer - that should be fun eh ? I have no velcro shoes though (even though I too am dyslexic)

warm regards