Turtle Power

Hi

I'm sure i have a blown head gasket - but difficult to confirm! I would appreciate any advice or comments that may assist confirming or preferably ruling out my diagnosis!

Car is an A4 (B6)2002 1.8 TQ manual with an AVJ engine it is serviced annually with all the usual bits replaced - oil, oil filter, plugs etc.

Recently (2 months ago) it had the oil sump replaced after it became clogged preventing oil moving around the engine, it was driven easily 20 or so miles with the engine oil light on (not by me - dont ask!) and hasnt been the same since.

Only fault codes i can find (with Vag Com and cheap OBD type connector) is the following

17544 Fuel trim:bank1(add):system too lean
P1136-001 - upper limit exceeded

I think that this may be indicating water into the cylinder via the blown head gasket and returns within a day when cleared.

So heres the details

- Car is generally running slightly rough, possibly not very noticable by someone who doesnt drive the car regularly. It has a feeling of powerloss / holding back. It will accelerate and idle ok in the most part but just feel like its holding back - often when being driven it will suddenly feel responsive and want to go like it used to do!

- not long after i got it back (after the oil sump replacement) I left it to idle on a cold day for 10 or so minutes and came back to find white steam/smoke issuing from the exhaust (enough that i thought car was on fire as it engulfed it completely and i couldnt see the car) i jumped in and moved it away from the house which stopped the steam! This happened once/after idling for five minutes and continued for 1 minute after driving away. Cant seem to replicate this since warm weather has set in but may also be due to additive added in next paragraph (both occured about the same time).

- coolant level fell so topped up and took to the garage but the garage could not find any leak with no sign of oil in coolant or coolant in the oil. They put some copper sealing additive into the coolant to either plug the leak and/or aid locating it if it continued

- I drove 10 miles today and checked under the bonnet after seeing small puddle on floor seems a small split in coolant expansion tank - but...

- ...found surging of coolant in the expansion tank. Coolant was draining to 1/4 level then surging back into it up to the lower end of the max / min markings, every now and then a small amount of this coolant would spray out of the split under pressure which makes me think that this split was caused by overpressure of the cooling system.

Any other details that you want to know please ask or if i havent explained anything too well again please ask me to describe again! I appreciate any help that you may wish to give.

Thanks

jschick

you would need to start with a compression test. the codes indicate you have a vacuum leak so check the vac lines.
hard to tell anything else the 1.8 is not known for blowing head gaskets but it's possible. if it is leaking you would have a sweet smell in the exhaust and likely run hot or bubble in the tank. but you generally would be getting misfire codes as well if antifreeze was in the cyl so at this point if it is leaking it is very minor

Turtle Power

Thanks for the reply jschick,

I have been checking the coolant constantly and i'm not seeing any bubbling or surging anymore ( i made sure that the coolant was level is correct almost every time i start her - maybe the surging was because the coolant was slightly too low, although it always seemed to be at worst above the inlet at the bottom of the coolant tank), the car stays rigidly at the 90C mark so is not overheating and the split seems to be a pressure relief valve? (please correct me if i'm wrong anyone) opening and closing occasionally. The running too lean fault keeps appearing along with the CEL and rough running - i will scour the engine for a vacuum leak and see how that affects things. I will also take the plugs out and see if there is any residue etc on them.

As a side note when the fault is reset the car generally runs alot smoother until it picks up the fault again and then runs more roughly - i'm guessing this is due to the ecu reverting back to the standard map table which runs it a lot richer hence more excessive fuel consumption.

If you have any other ideas or thoughts on this problem please let me know,

Thanks

ECS Tuning-Audi

Whats your oil look like??

Jason

Turtle Power

Hi Jason

Currently it is a dark brown used oil look - no signs of white gunge or milky appearance to it (last oil change about 6 months ago) or around the cap or dipstick also no signs of oil in the coolant either.

Turtle Power

Ok left it to idle for about 20mins and had some 'smoke' come out, as you can see in the picture and video the smoke is white and isnt oily (which i beleive would be blue and smells of burnt oil!). When i put my phone case in front of the exhaust some condensation appeared so i'm pretty sure the 'smoke' is steam.
This steam disappears when the car is reved above idle or when being driven.

Have also checked the plugs and no evidence of coolant on them and still no other codes other than the 'too lean' code that i have mentioned before - i'm sure a broken small bore braided vacuum tube from the end of the inlet manifold accounts for this (hose purchased and will be fitted tomorrow).

More bubbling and surging in the coolant tank which periodically dumps via the pressure relief after a drive and was idling again! Still no sign of oil in the coolant or coolant in the oil!

Should there be a regular flow of water through the coolant tank as it stayed cool throughout the idle only getting hot after i drove it which is when the surging etc occurred.

So unless there is some alternative route for coolant water to get into the exhaust then i cant think of any other problem other than head gasket which = alot of grief
A4Exhaust.jpg?t=1302885020

Video below (opens new page)

Turtle Power

I traced the vacuum leaks to the secondary air system via two destroyed hoses - one goes from the combination valve (silver round valve at the rear of the engine bay close to where the crankcase breather hose comes out) to the secondary air inlet valve (n112) which is mounted under the intake manifold. The other goes from the turbo charger air recirculation valve (n249) again mounted under the intake manifold to the port on the end of the intake manifold this is opposite the throttle body inlet.

Both these hoses were about 10mm in diameter and covered in cotton like braid (like a footpump hose) which was hiding the fact that they were both degrading and just turning to dust in places. New hoses are on and the pick up and general performance has returned - infact the car feels really good especially when pushed.

Thanks go to jschick for pointing me in the right direction with that

Still unsure about the steam that occurs so far only from a cold idle (10 mins or so of idle). The coolant leak isnt a split in the coolant tank, it was coming out of the tube that the pressure relief valve in the lid discharges into.

Since i fixed the vacuum leaks the coolant leak situation seems to have stopped but i cant really understand how vacuum leaks could possibly affect the coolant system over pressurising it and causing surging - am therefore expecting this situation to continue at some point.

Jlewis50

Do a proper leak down test onthe vehicle. Not very expensive and will give you the answer

Jlewis50

Do a proper leak down test onthe vehicle. Not very expensive and will give you the answer

Turtle Power

Thanks for your reply and sorry about the delay in getting back to you. I will see if i can get someone to assist me in doing one (no compressor or tester!).

I guess i would be looking for something like bubbles in the coolant header tank?

I'll let you know what i find if i can get someone to test it for me.