Avoid GUNK engine cleaner, especially on the 3.0

[slacktide]

So I picked up a 2002 Avant 3.0 about a year ago. One thing I noted is that the engine bay was super clean. Over the first few months of ownership, it started a slow coolant leak that got progressively worse. I ended up pulling the intake manifold and replacing all of the O-Rings on the coolant pipes. Most of them looked good, except for the one at the forward end of the lower cooling pipe. It was all swollen up, and super soft, about the consistency of a gummy bear. Also, underneath the IM it stank strongly of the familiar smell of GUNK engine cleaner. I suspect that the previous owner used GUNK engine cleaner and either let it soak in really good, or didn't rinse it thoroughly, and that O-ring was soaking in a puddle of GUNK for a while.

A while back I was doing some work on my electrical system and used DeoxIT contact cleaner. If found that it quickly made the silicone seals in the contact housings swell up, so bad that you couldn't get the connectors to mate together, and I had to replace all the seals with ones I salvaged from a junkyard. I suspected a similar compatibility issue with GUNK and O-rings, so I decided to try an experiment. Also did the same with contact cleaner and silicone electrical seals. Pics speak for themselves, hope this helps someone.

[caluma4x4]

Truly shocking, think they've overlooked the reaction with rubber engine seals, shared on Audi Facebook group.

Sent from my MAR-LX1A using Tapatalk

[EuroxS4]

Any petrolium based product will swell seals. This is nothing new. put a o ring into gasoline for a couple days. Samething will happen.

[Spike00513]

I mean on one side, you'd hope people aren't soaking an engine in cleaner for 24 hours

as opposed to spraying it on a warm engine to brush and rinse off
That being said, I wonder if Gunk is just a regular degreaser,
and if all other degreasers would do the same thing
If that's the case, I'm not really sure how to detail the engine bay then

[Kevin C]

Pretty much how transmission seal saver works.

Last I checked gunk is pretty much kerosene with an emulsifier so it can be washed away with water. The O'Rings are probably made from EPDM. The coolant temp sensor on the back of the head on my 1.8T had the same swelling issue.

Being non-polar elastomers, EPM and EPDM offer good performance in polar fluids such as alcohols, water, steam, coolants etc., but perform badly in nonpolar fluids such as hydrocarbon oils, lubricants and greases.

[EuroxS4]

Pretty much how transmission seal saver works.

Last I checked gunk is pretty much kerosene with an emulsifier so it can be washed away with water. The O'Rings are probably made from EPDM. The coolant temp sensor on the back of the head on my 1.8T had the same swelling issue.

Any type of stop leak,barr's aka amazing money saver stop leaker unicorn magic fluid they sell at the autoparts store thats all it does is swell the seals 9 times out of 10 creating a bigger problem than already exists. LMFAO

[Kevin C]

Any type of stop leak,barr's aka amazing money saver stop leaker unicorn magic fluid they sell at the auto parts store that's all it does is swell the seals 9 times out of 10 creating a bigger problem than already exists. LMFAO

I have pulled a few engines apart after they had bars leak and hadn't seen a seal issue probably because the rest of the motor melted down from a partially clogged radiators going to fully clogged and warping the head before the seals were damaged. On auto trannies I have had apart with seal saver, the clutch pack seals that came out were enormous! It was kind of amazing how big the seals got. Not sure how much had been added but the solvent smell was horrible.

Pretty sure the one on the back of the head on my 1.8T was just from small amounts of engine oil over time. It looked to be the original seal at 170,000 and none of the other seals were bad.

Same thing with with the seals in the brake system if they get exposed to engine oil.

[EuroxS4]

Yeah I have seen that. I can’t tell you how many people come in with coolant leaks from the rear flange and cts and we tell them we can change it but you should really do the VCG and CTG to fix the oil leak or it will happen again and swell both o rings. People never listen.


Sent from my iPhone using Tapatalk

[Turbo510]

...it started a slow coolant leak that got progressively worse. I ended up pulling the intake manifold and replacing all of the O-Rings on the coolant pipes. Most of them looked good, except for the one at the forward end of the lower cooling pipe. It was all swollen up, and super soft, about the consistency of a gummy bear.

Really an excellent write-up, I like the lab analysis look; more like a tech article.

My '05 is back on the road after dealing with the exact same thing - gummy, leaking 0-ring where the plastic manifold plugs into the block. I also changed the other coolant rings, plus intake manifold seals and injector O-rings. The leak is gone, and with new O2 sensors installed, the car indicates 28 MPG average on my 45 mile commute, despite doing 75~85 MPH practically the whole way. And just went past 230,000 miles too.