Been having a small issue with losing coolant over time. Got a radiator pressure tester the other day and pumping it up I could see a sign of a leak behind the water pump. Well it looks like it may be the coolant temp sensor that's leaking. It's too hard to see with everything assembled so I did try one thing and worked some paper towel under it and it got wet very quickly.

I'll have to tear off that junk in front of it and pump it up again to confirm, but it's hopefully not an all day replacement but who know with all that looks like will have to come off first.

Wish me luck.

I haven't worked on a stock engine in so long I can't recall if the emissions stuff is in the way. If that's the leak it should be a pretty simple R&R. I hope that's it for you.

The coolant temp is right on the intake manifold, below the goose neck. Shouldn't be that hard to swap out.

I was thinking... is it the sensor? it could be the threads.

remove, add some teflon tape or RTV and reinstall.

I ordered a few parts, some for the shelf and a couple 'just in case'. Getting ready to do some more digging in but haven't yet. Thought of an idea to try and nail it down a little better prior to either doing it myself or getting it to my mechanic. Looking at the FSM it looks like if it's the water pump, that could be a bear as the FSM lists having to remove the a/c compressor and fuel lines first to get it off.

Had what I think was a brain-storm yesterday. I cut a piece of cardboard and after a little bending to soften it up was able to slip it under the air pump and work the end between the top of the water pump and the coolant temp sensor and pumped up the cooling system. I got coolant on the engine side of the cardboard but not on the water pump side so looks like the leak is the easier of the 2 or 3 possibles.

Looks like I'll have to pull that emissions pump to gain access to where it's leaking from but that looks a lot easier than pulling everything off to get to the water pump. I won't know for sure till I tear it open but hopefully it's either that sensor or that U shaped hose rather than the water pump. If it turns out to be the water pump, unless I can find a way to get the a/c pump out of the way, I'll likely let my mechanic do it otherwise I expect to fix it myself (I hope).

The a/c clutch looks to be going out, does a lot of squeaking, I picked up a reconditioned unit, and if I do the repairs myself I'm thinking I'll do that at the same time.

Time will tell, hate doing anything mechanical in these cold temp times. Unfortunately I don't have a heated garage.

Happy Holidays everyone.

Sounds like you've got some investigative work to do. A pressure tester will help narrow down the source. That u-shaped hose us for the coolant to go through the throttle body. Now is a good opportunity to eliminate that and do the "throttle body bypass" and send the coolant directly to the heater core via a longer coolant hose.

The water pump is a fairly time consuming job. As far as removing the ac compressor, on the 89 you just unbolt it and move it to the side, no need to disconnect the lines. Not sure on yours. But if it's going bad, now is a good time to change it anyway.

Good luck.

Post up some pics!

Well I spent a little time out in the garage and found the leak. It's the U shaped hose that goes from the intake to the block. I had picked one up the other week and it's blue vs black. I think I'm going try and find a black replacement locally as I don't like the looks of the one blue hose under there. I thought about checking out eliminating it, but with driving it at times when it's very cold out, I think it's probably better to have it on.

I did take some pictures so far and will take a few more and post them once I've got it done.

I eliminated mine and had zero ill effects, if that helps. Chicago gets pretty cold, too.

I wanted to get a radiator pressure testing setup but I couldn’t find one with a cap adapter that fit this car. I ultimately found that H.F. had a setup with a generic adapter that worked. Screw the seal part in, clamp it to the radiator neck and turn the knob on it to tighten it up tight. Snap on the pump and pump it up

[URL=http://s162.photobucket.com/user/hcbph/media/Corvette/Coolant%20Leak/DPP_0011_zpsdgi8wro7.jpg.html][/URL]

I found it was the throttle body heater hose that was leaking on the bottom fitting.
The process I used to replace it was first to remove the fanbelt. I then removed the MAP from the throttle body, marking the connector

[URL=http://s162.photobucket.com/user/hcbph/media/Corvette/Coolant%20Leak/DPP_0008_zps3gjii0vy.jpg.html][/URL]

There’s also a couple of devices next to the airconditioning compressor. I marked the units and wires and unhooked them. There’s also a hose that comes off the airpump and goes to that diverter valve, I also removed that and marked it.

[URL=http://s162.photobucket.com/user/hcbph/media/Corvette/Coolant%20Leak/DPP_0010_zpsa6jmkp0v.jpg.html][/URL]

At this point, though the radiator showed full, the leak from the bottom of the U shaped hose between the throttle body and block was not leaking. I left the radiator cap on to try and keep a vacuum and not have coolant run into the block and jacked the front of the car up having already loosened the hose clamps on the existing hose. I’d picked up a Dayco 87653 hose at Autozone along with a couple of worm clamps.

[URL=http://s162.photobucket.com/user/hcbph/media/Corvette/Coolant%20Leak/DPP_0009_zpsozqw46k2.jpg.html][/URL]

I did find it made it easier to fit after removing about 5/8” of hose for the bottom connection on the engine. I had loosened up the hose clamps on the old hose and worked it off. No coolant came out of either fitting. I slipped the hose clamps onto the new hose so they’d be available to tighten once on. I put the lower hose fitting onto the block and tightened the hose clamp. Before putting the upper on on the Throttle Body, I pulled it out and routed the wire with the 3 connectors (MAP, air divertor and whatever the 3d one is) through the loop. Next I put the upper fitting onto the throttle body (just to the right of the yellow arrow).

[URL=http://s162.photobucket.com/user/hcbph/media/Corvette/Coolant%20Leak/DPP_0010_zpsa6jmkp0v.jpg.html][/URL]

Now it was just a matter of testing the cooling system and reversing the process to put it all back together. Once the hose was on, I pressurized the radiator with 13 lbs of pressure and left it a while. It did lose 3 lbs over 30 minutes, that I attributed to the universal cap adapter as the most likely vs a leak yet in the cooling system. Did soap and water on the hose ends and didn’t get any bubbles. Once comfortable it was tight, I just reversed the process to reassemble the car.
Lowered the car and started it up. The radiator showed full when I lowered the car but after about 3-5 minutes of running it, the low coolant light came on. Temp showed about 110 degrees so I opened the radiator cap and the radiator showed low so I filled it up along with the overflow tank.
That pretty much wraps it up. Happens I had a low coolant light come on during the trip home when I purchased the car the other year. It’s likely been leaking some time but never enough to become truly suspicious and most of the coolant on the garage floor so it wasn’t too visible. Anyway it seems to be fixed now.
Next will be replacing the a/c clutch and the bushings in the rear end. Hopefully they will go as well as this did.

Great write up! Glad it's fixed.

Quote:

You and me both! Ironically I've looked over the old hose fairly well, I can't find where it was leaking but I definitely saw the spray coming out of the bottom of it somewhere where the hose was on the fitting. Don't have a small enough mirror to fit under where it was leaking I took it on faith it was the hose so just so long as it's leak-free, I'm happy.

Happy Holidays everyone.

It is possible the hose was not leaking due to a hole but rather the hose got hard and brittle and no longer sealed effectively around the outlet nipple.

[quote]
Matatk wrote:
It is possible the hose was not leaking due to a hole but rather the hose got hard and brittle and no longer sealed effectively around the outlet nipple.[/quote


Yea, that happens after a few years! Then the pot metal housing gets corrosion around the neck just adds to the problem.

Joel

Joel is 100% correct as well. I hope you cleaned the surfaces first before you reinstalled the hose.

I buy Scotchbrite pads by the box, so yes I did what I could to insure everything was nice and clean.