The Mysterious Coolant Leak

[b7a408]

Hello All,

It's been about a year since I noticed a small coolant leak forming under my car after driving it and letting it sit. During the past year, I bought two gallons of coolant and topped it off (50/50) every few weeks. Here we are a year later and I still can't find where the leak is coming from. I'm at 110,000 miles and it's time to replace the timing belt and water pump. I'd hate to have it done and not get the coolant leak fixed.

My thermostat works fine (was replaced 30K-40K miles ago). Everything in the front of the engine is dry and around the thermostat is dry also. Everything around the CTS in the back is dry also. I noticed a small puddle/wet area right behind the oil filter on the block. I took it to a mechanic to see if we could find the leak. He pressurized the coolant reservoir tank and lifted up the car but no leaking/dripping. I assume because the car was still warm. I'm attaching few photos of my situation. What is the metal box #43 in the diagram?

Thank you

[deusilan]

That's your oil cooler.

[wding2000]

My guess is: if it is not oil, then it may leak coolant from oil cooler or its gasket.

[vce1232000]

That is your oil cooler. most likely the gaskets are toast.
Here's the
https://www.europaparts.com/oil-cool...06d117070.html

[Theiceman]

I think there are two gaskets.

[vce1232000]

I think there are two gaskets.

The other gasket is the oil adapter to the block. That does not need to be ed unless you remove the whole oil housing adapter. The oil cooler itself can beed without the housing from the block. But the oil adapter housing gasket is this https://www.europaparts.com/oil-filt...06f115441.html. I would both since it makes since due to age of the gaskets

[b7a408]

Thank you all for the replies, appreciate it a lot. I took the car to a second mechanic who also let it sit and he also failed to find the coolant leak. I think you guys are correct that it might be a gasket or gaskets. He did say that he noticed an oil leak. Looks like there is a small oil leak and a small coolant leak. Is this an expensive repair?

Thanks for the help

[miA4]

Why not pressurize the coolant system to see if it'll leak?

[b7a408]

We did twice and nothing leaks. I think it's only while car is cooling down and once completely cold there is no leak. I let the car sit 3 or 4 days and small puddle doesn't increase and coolant level in reservoir stays the same

[Cobra351]

We did twice and nothing leaks. I think it's only while car is cooling down and once completely cold there is no leak. I let the car sit 3 or 4 days and small puddle doesn't increase and coolant level in reservoir stays the same

Just a reminder as I had this happen recently- did you check the coolant flange? Leak on the passenger side of the motor, near the exhaust manifold.

[papadelogan]

Just a reminder as I had this happen recently- did you check the coolant flange? Leak on the passenger side of the motor, near the exhaust manifold.

Is there a thread about that, some pictures, or ideally, both?

[Low and Behold]

Is there a thread about that, some pictures, or ideally, both?

Tons. Search rear coolant flange.

[b7a408]

I think I've figured it out. Diagnosis: there are two issues:

1) I looked again yesterday and noticed dried coolant on the bottom of the engine oil pan. The coolant trickles down from behind the thermostat. I was able to see some coolant and took few photos. Thermostat works fine and has been for a year since the leak appeared.

2) Small leak (oil and/or coolant) most likely coming from the oil cooler gasket area. This leak is the one visible in the photos I posted earlier in this thread.




My goal is to remove this small puddle and see if coolant fills the little hole again.

[4rings5stars]

Dollar to the dime, if you pull the alternator you'll see coolant residue in and around tstat fittings. Just redid mine(Had a crappy Wahler) and the residue was there and it leaked exactly like yours. Remember, fluids love to travel obfuscating their origin.

[b7a408]

Thanks for the info. Looks like my oil leak is exactly the same as this thread http://www.audizine.com/forum/showth...-behind-filter

Luckily, I'm not losing much oil yet (adding half a quart between oil changes) but I'll keep an eye on it.

[b7a408]

I finally got a chance to take out the alternator and take a closer look at the thermostat. The process isn't hard but I wasted some time on two things. One, I didn't want to break the connector on the alternator and took my time trying to push it down and out. It wasn't working so I settled on using a pair of pliers to apply pressure down on the clip. Two, right before I was about to put the accessory belt back on the alternator it came off the vibration damper. There wasn't enough space to get it back on with my hand. So, it took me a while but I came up with a solution to insert a thin black cord and pull the belt in place. It work and I put everything back together.

As for the thermostat/coolant leak, I used some paper towels to soak up all the liquid. I'm sure it will come back and when it does, I'll go in and replace the thermostat.

[StanShepel]

Besides the T stat leak, i had same problem 1 week after i replaced the t stat saw leak rolling down and followed it up. Ended up pinching a small part of the o-ring. The other small leak i had was a plastic fitting behind your engine. Connected to the CTS housing that ran to the heater core. This thing leaked good only when heat was on. One way i was able to round it down. The plastic parts all had small cracks from heat and such. That was a pain to find.

[wding2000]

The other small leak i had was a plastic fitting behind your engine. Connected to the CTS housing that ran to the heater core.

That is coolant flange.

[StanShepel]

That is coolant flange.

Well that was one part, the other is the plastic tube farther back behind the engine. More to the right if looking from the front.

[B72011]

I have a very slow, drip, drip.....maybe 1 drip every 0-30 sec--its coming from the oil cooler area. I will have time after the holidays to address it. In the meantime I planned on using this stuff. OldGuy on here used it for a time with a radiator leak......https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
Aluminum Bars Leak.
Anyone else used the stuff for a slightly larger than pinhole leak? What was your level of success.
Not worrying about introducing it into the car. Have no reservations about using it--I dont think it will harm anything. I'll flush later.
Anyone else use?