Anyone had this problem?

Took a ride Sunday and temp skyrocketed quicktime. My plastic petcock was already stripped, but didn't leak. Until...

Anyway, options here???

the threads? or is the little t-handle thingy broken?

There should be a bolt there you can access if the handle has broken.

Otherwise, remove the rad and let someone look at it. If that's busted, I wonder what else is...

Tabs aren't broken bogus - I think the threads are stripped; will find out in the AM here.

But about stripped threads???

Hard to say without seeing it first.

Is it reverse thread?

I don't remember, but I have a stock draincock in my toolbox I can check when I get home.

take it to a radiator shop

They're either fix it with a pressure test or tell you to replace it.

I went aftermarket after I cracked _both_ side tanks at a road course

PEtcock isn't stripped...

Up on jackstands, and filled the reservoir, and it DIDN'T run out as it did when level (and I couldn't tell where THEN).

More diags to do here........................

Like Brian mentioned, these radiators are known to crack at the side tank where the metal connects to the plastic. Mine did.

Under pressure the leaks show up way fast.

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Pressure test SOMEtime today, I hope.

Thing only has 37k behind it. Time kills rubber, plastic, but hardware?

there is a rubber seal between the tank and core... also a rubber o-ring in the drain...

Also, side tanks normally are plastic.

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AS DID MY 87. REPLACED IT WITH A DEWITT & AM VERY HAPPY WITH IT.

The stock petcock IS plastic. At least mine was.

You can dye test the whole system but the kit will cost you $60

Pressure test cold wouldn't push a leak.

Filled the reservoir with a quart, ran it 5 minutes, and it stayed full.

NO reading on the temp gauge after 12-15 minutes.

And no leaking showing post 10 minutes shutdown.

I'm at a loss.

Next plug in DataMaster, and see what shows there, if anything.........


???

The coolant WAS pushing into the reservoir, while I had it open.

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Normal

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I was presuming that told me good pump function...

Well, a waterpump can wear out , probably takes 500,000 miles.
If you open the throttle off idle, that flow will increase and the level in the tank will drop slightly.

THinking on this this morning...

Yesterday, as I noted above, the dash temp gauge appeared inoperative. Didn't move after almost 15 minutes.

So if CTS is toast, then ECM will never tell fans to come on.

Correct?

With a good thermostat, there will still be flow through the radiator, but insufficient cooling. And a hose will blow (or a missed tightened clamp will let off).

Problem is, I THINK I noticed the dash temp gauge PEG immediately before shutdown last week.

So, could the CTS START failing, and then COMPLETELY fail???

S120, in FSM, is a Splice; is it not?

Does CTS have ANY grounding function integrated into CTS body?

And just realized something ELSE...

If my CTS is bad, why no black smoke when warm yesterday?

And AS WELL, I think I have no leak. The coolant 'leak' was from Overflow Reservoir OVERFLOW.

I checked the overflow reservoir, and it has coolant in it. And I NEVER put coolant in it.

That would explain no leak on Pressure Test...

I pressure test mine by purging it, getting it warmed up to the verge of turning the fan on, shut it down and observe/listen for 15 minutes. Pressure peaks with the engine off and dumping heat into the system without flow. I also have my radiator upper shroud trimmed so I can remove it with all hoses connected.

You shouldn't ever get more than a slow dribble into the overflow as the cap relieves expansion into there. And you better have some extra in there for when it cools back off and draws a vacuum to suck it in. I always overfill my coolant reservoir after purging/filling in case of any air pockets. Too much though and it will spill over when really hot.

Is the dash sending unit and ect sensor one in the same on the lt5? Or does it have two sensors?

I'm about 99% sure only one sensor there CC; found all pertinent schematics + diags in FSM.

CTS Sensor test is straightforward. Getting @ it is NOT - means a plenum pull, unless I can figure out a way to test at the leads coming out of ECM harness connector, with backprobes (which I've done on LT-1)...

I've identified the sockets in the ECM connector - in the schematic below - the Yellow 410 + Black 452 wires.

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I can cut the Yellow 410, and re-splice with total confidence.

Then make a jumper, to ground out Circuit 452, and observe the gauge.

Question is, would the test be accurate withOUT cutting Circuit 452, leaving the CTS Sensor itself connected on 452.



???????????????

I ran it just now. Dash Coolant Gauge DID come off of cold, but JUST BARELY, after 10 minutes.

FSM says that CTS CAN shift 'Out of Calibration'.

A small PART of the mystery is solved.

It's no wonder that the 'Coolant Gauge' hardly moved - IT WAS THE OIL TEMP GAUGE!!!

12 QTS OF OIL TAKES A WHILE TO WARM UP.

The coolant gauge was moving accordingly.

===========================

But the mystery of the boilover last week remains.

I plugged in DataMaster just now.

Coolant went to 208, and the Primary Fan kicked on as it should (Haibeck's Chip Encoding). Coolant then went down to 197, as it should, and the fan kicked off.

CTS works.

Fans work (tested A/C Fan Circuit too).

Petcock does not leak. No leaking whatsoever.

I was driving moderately when it boiled over.

Why did it do it???????????????????

Possible stuck thermostat, then cleared itself?

Joel

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Like

If the fans are coming on, I'd test the thermostat

Had a radiator block up on me once.

It was only using half

I think the stat might have had a deposit in the shaft that the spring rides.

Blocked it when it boiled over, then cooled, and next time it knocked off the deposit.

???????