Wicked Coolant Leak - What Gives?

[Toms88]

Yesterday I experienced a sudden onset coolant leak after a short drive. Coolant was literally streaming out at the back of the block between the oil pan and the transmission pan. The leak continued for 5 minutes or so and then more or less stopped. I restarted the car for a few seconds and the same thing happened. I restarted again and pulled up on ramps. After the leak started slowing, I got under the car and it appears the leak originates above the oil filter, under the #7 plug, and in the area of a sensor (?) that is in the block below and to the rear of the oxygen sensor. I admit I am guessing about the location but it's hard to see the area. There is no coolant visible around the intake manifold. Also, there is, I believe, a freeze plug near the above mentioned sensor(?) and the plug seems intact. The engine runs normal, nothing unusual from exhaust, and oil on dipstick looks fine. Any ideas on what I'm dealing with or how to proceed ? Thanks

 

[tnovot]

coolant leak

If you could rent or borrow a radiator tester, let the engine cool, clean the area around the leak, pressurize the cooling system, and use a good light to find the leak.
Assuming you are confident that the leak is not coming from the rear head area and can't be a leaking intake gasket, I'm betting on the freeze plug.
Terry

 

[jmccloud]

Sounds like the knock sensor. Pinch the connector to remove the electrical lead, then you can see a lot better. They're about $35. The one on the 'odd side' (1357 cyls) is harder to remove because the angle prevents getting a socket on it straight. I bought a big pair of water pump pliers (channel locks) just for the job and they worked well. I have a '95 that has 2 knock sensors, one on each side screwed into the block drain. Not sure if your year is the same.
Hope this helps.
John
PS, If it's the knock sensor, there will be very little coolant remaining in your block. Don't run the engine.

 

[cosmo]

bring it to chevy dealor

 

[grapeknutz]

bring it to chevy dealor

NOOOOO DONT DO THAT!!!!!!

 

[tnovot]

Ditto

 

[Mart]

Gotta agree, not a dealer, they will only fix the bulge in your wallet.

Did you check to see if it is coming from the back of the intake, thats a common place to leak.

Mart

 

[BigRed]

LOL Bring it to me! Dealer Smealer BAH!

A few possibilitys

Cracked head or block...no no no no
Intake
Knock Sensor
Freeze/heater plugs

You've got do what Tnovot said, you've got to pressure the system with a pressure tester then look for the leak. Try to clean the area first the get the best results. Using a black or UV light is best because is will actually make Dex or Standard coolant glow.

Judging from the stream your talking about this is a no brainer so you could probably forget the light.

Don't EVER be scared to do things yourself...If you get into trouble we can help you through it.

 

[Toms88]

First, thanks for the responses to my little mess. After doing some more checking today, it looks like the leak is actually coming from the upper back driver's side of the block-straight above the oil filter. It is an area you just can't see either from above or below. I've looked straight down next to the wiper motor with a 500 watt halogen light and I still can't see the source. I can feel the coolant on the back of the cylinder head below the back of the intake. I guess the most distinguishing feature is that the leak is the same with or without the engine running and continues until the overall water level is presumably below the leak. I hate to admit it but I was thinking of having the car towed to the dealer tomorrow. I'm worried about anybody messing with the car, but I guess my feeling was that the dealer is more obligated to stand behind their work even though I might be undergoing a wallet flush.

 

[Edmond]

I'm worried about anybody messing with the car, but I guess my feeling was that the dealer is more obligated to stand behind their work even though I might be undergoing a wallet flush.

The dealer is not more obligated than anyone else to stand behind their work. In fact, we hear more bad stories than good stories on dealer repairs. If you really don't want/have time to tackle this project, I would suggest starting a thread about local Corvette mechanics in your area and get suggestions.

 

[Rain]

passed the link on to a friend. Think he had the same prob with his 89.
Should drop in on this thread tomorrow - hope it helps
Rain

 

[Magmotor]

Same exact thing happen to my '89, only the passenger's side. No matter where we looked, couldn't find the leak. Had to put it on a rack and remove the starter motor and move the main wiring harness to get a hand up far enough to feel where it was coming from. Sure enough. it was a head gasket leak. My two cents say's the same with yours only you don't have the luxury of moving stuff out of the way on the driver's side to find it. Whatever you do, don't take it to a dealer. It'll end up costing twice what a good mechanic shop that deals in heads will cost you. BTW: you might as well replace the water pump while the engine is that torn down. Will save in the long run....good luck with it...!!

 

[brookman]

Do you have the factory oil cooler? The hoses go in directly above the oil filter.

 

[RedRagTop]

bring it to chevy dealor

Now just hold on a minute here. Someone will come on with the sure problem/solution, there is enough experience here to build your car from scratch in the dark. Give Rain's bud a chance...

 

[RedRagTop]

Just curious though Tom; Was it parked for the winter? How many miles on her?

 

[The Car Whisperer]

Do you have the factory oil cooler? The hoses go in directly above the oil filter.

I would definitely check to see if you have the optional oil cooler like Brookman said. There are 2 hoses associated with the cooler that get very neglected and you might have a leak in them. Sounds like an easy fix if it's not the head gasket.

 

[cosmo]

why not if your stuck on a problem or who shoul he go to

NOOOOO DONT DO THAT!!!!!!

message above

 

[c4cruiser]

Chevy dealers are usually higher priced in terms of labor charges compared to independent repair shops. In addition, most dealerships no longer have "factory-trained" technicians that have specific Corvette knowledge or experience. If you need parts, dealers will, in nearly every case, use only GM/AC Delco parts. While there is nothing wrong with that per se, most parts made for the aftermarket are of decent quality and much cheaper.

You can find lots of horror stories here and on other forums that describe some bad experiences at dealerships. And on the other side, there are some people that have had tremendous luck with their Chevy dealer. If you have a dealer that cares about repairing your Vette correctly the first time and at a fair price then you have a good dealer. If you have a dealer that does not do good work or care about your car or the parts and labor is much higher than what you expected, you should go elsewhere.

The overheating problem described is one that a dealer would probably charge a lot of time for diagnosing and would probably recommend replacing more parts than what is necessary. For example a simple freeze plug that a dealer uses (AC Delco) could cost 3 times as much as one you get at Autozone. The dealer would probably charge the standard labor rate for that R&R of the part where a small shop would either agree on a price up front or charge only for the time it took to actually do the work. Techs at a small shop may have a lot of "tricks" they learned over the years where a GM tech may have to do a repair by following a service manual.

So IMHO, the "take it to a dealer" idea is not always the best way to go.

 

[Toms88]

UPDATE - I spoke with an independent mechanic today and he said the most likely culprit is one of the two freeze plugs on the back of the block. He based this on the amount of leakage, nothing white from the exhaust, no cross contamination between oil and coolant, and no loss of compression. Of course, nothing is certain until it gets to a shop. I'm sure it will be expensive but I look on it as an "improvement" rather than a repair (lol).

 

[taegdh]

But you also have a freeze plug just forward of the oil filter mount on the side of the block, and I've seen those go before the ones on the back of the block.

Were it one of the ones from the back of the block, the coolant would be dripping from the bottom of the bellhousing. The freezeplug just forward of the oilfilter would let it seep all over that area. That's where I would look.

It will be difficult but no impossible to replace on a vette, but if you can, swap ALL of them. There are six (6) in all, two on each side and two on the back, (you'll have to take the flywheel off to do that), and you won't have to worry about it happening again, unless you let the antifreeze get too thin and it colder than a whore's heart!