kingtaco

Hi all, thank you for the great help I've received in the past. I'm now looking for some advice before I tackle what must be a bad head gasket.

Vehicle info:
1995 90s 2.8 AAH
208k miles

Now here is the sequence of events and symptoms:
-Bought the car in September and there was some coolant leaking from the upper and lower radiator hoses (i knew this at time of purchase). I tightened down the worm clamps and the leaks went away for awhile then came back.
-Bought new upper and lower hoses. Upper no longer leaked, Lower hose still leaked, from all 3 junctions. I wrote it off as 'damn I spent $50 on that hose and it must be a lousy aftermarket fit.'
-Fast forward, I did a timing belt, water pump, and t stat job just to make sure everything fresh and in it for the long haul (nothing to do with expecting that to stop any leaks), at which point I added some water pump gasket maker to the lower radiator hose connections hoping to seal off a "lousy fit." No luck.
-Fast forward to recent time- More coolant leaks have developed. The left side of the radiator is leaking. Also the driver side hose going to the heater core is leaking and is possibly the biggest leak of all. Finally, it looks like there is some leakage at the coolant hose going to the oil filter housing (oil cooler?).

More helpful info:
-It seems like the car is only actually losing fluid after you shut the car down and park it. When it is running and idling, there isn't any visible leakage, and if there is it would probably require idling for 10+ minutes to create any leakage.
-I do have an O2 sensor CEL (2342 code, g39 I believe). It only comes on at idle after the car has reached operating temp. I was planning to replace that when/if I had to take the heads and exhaust manifolds off.
-Definitely some engine oil leaks primarily off the right/passenger side of the engine.
-Idle might be a little off, but still very smooth

-Aside from that the car runs like a dream. It pulls nicely. I've taken it on very long trips and drive it daily for work. No overheating.

Thanks for reading everything. What would you say is the most likely cause? I can only assume exhaust gas is entering the system and it needs to find a way out anywhere possible. Where can I start troubleshooting aside from going straight for the heads? I have not run a compression check, but I know that would be a good start.

Rusty Spokes

You may want to get a block tester. Available at most FLAPS. Test and see if you are getting any combustion gases in the cooling system.


Test or replace the pressure cap and be sure your coolant tank is not leaking too.

kingtaco

Thanks that video was awesome! I've seen the kit and thought $50 was too much to spend, but after watching that it seems super easy to use and I could definitely put it to use on other cars.

I didn't mention that I actually dyed the coolant so I can clearly see anywhere it's leaking from. No visible leaks near the expansion tank at all. What would be the purpose of pressure testing the cap, and how would that have any bearing on the many leaks throughout the rest of the system?

Rusty Spokes

The coolant cap should be releasing pressure at about 14psi (1bar)..sometimes they don't release pressure or are calibrated too high..like 22psi or more. then you get leaks.

Your symptoms could be a bad cap..as it leaks when you shut down after driving. The engine/coolant will "heat soak" when the engine is turned off..and no cool air is coming through the radiator and the engine is hot..the coolant temps will tend to rise is the block and the bad coolant cap will not "burp"..and you get leaks.

The part number should be 443121321, double check.

Rusty Spokes

And be sure your cooling system is properly bled with no air in it..do it by the book.

hubturn

As to the O2 sensor code. Before replacing the O2 sensors, understand that this code is stating that there is an out of limits relationship between the composition of air going in and exhaust gas going out, as analyzed by the ECM. It is not necessarily a bad O2 sensor. You could have a bad throttle body gasket, a cracked hose somewhere letting air in, or, as happened to me, a dirty Mass Airflow Sensor. Naturally, that was discovered AFTER buying two new O2 sensors, the tools to get them in and out, replacing them and then still throwing the O2 code. To give credit where credit is due, Crazy Russian steered me in the right direction on this. A $3 can of Mass Airflow Sensor Cleaner did the job. I know you have bigger issues, but store that one away in your so-what file for later.

kingtaco

A little update:

Shout out to rustyspokes it seems like the cap is causing the issue. I bought the block test kit and absolutely zero sign of combustion gas in the coolant with a cold engine, warming up, and after a long test drive.
Also zero signs of leakage with the cap off and the car not running so I have my fingers crossed the cap is the perpetrator.
Went to the audi dealership and they would have had to order the cap for $63... I told them pass so now im in search of a cheaper but also genuine option.

Regarding other responses:
I'm well aware of the importance of bleeding the system. It is bled properly and I'm not concerned with that as a cause for leakage.
Also, I understand how O2 sensors work and I'm also aware it's rarely as easy as replacing the sensor, however I priced the Bosch upgrade listed on 12V.org and at $10 each it seemed like money I was willing to spend. However, absolutely good looks on cleaning the MAS. I'll definitely give that a go.

Rusty Spokes

You can use a Febi 02269 cap..I've got one on my car. Avoid URO caps

About $4 plus shipping: http://www.autohausaz.com/pn/02269

kingtaco

Decent! Ill order that asap and have details on the situation to follow.

For now im running the cap just barely snug and we'll see if that makes a difference.

Rusty Spokes

King..did the cap help?