1.8T a4 cooling fans never go to high??

[EuroxS4]

Hey guys so long story short.I replaced the engine in the a4 i purchased because it was badly overheated and had no compression but it also needed coolant hoses,So I replaced all coolant hoses and coolant flange as well.Currently not throwing any faults.However the vehicle is not being driven as it is no registered at this time.So I topped off the coolant once everything was back together.Today I held the revs around 3k rpms in order to pressurized the system and get it to bleed all the air out of the system.However I am running into a problem.Coolant system is pushing coolant out of resovoir bottle after holding the revs.When removing resovoir cap no pressure is released.

The car is not over heating the gauge never goes past half.However I noticed even with the a/c on high the coolant fans never go to the high setting.Just looks like they are spinning on low setting.I ran the output test through vcds andthe fans went to high.So my question is this.Can I still have a bad fan control module???or is my issue a faulty coolant temp sensor??With no faults stored I would assume all the coolant temp sensor and switches are good.

[old guy]

It sounds like you may have a defective coolant reservoir cap. The cap is designed to hold between 22 and 23 PSI. So nothing should go out through the cap until you are over those pressures. If it's blowing out of the cap but when you remove it there is no residual pressure that would indicate that either the cap isn't working properly or you have a substantial leak somewhere else.

[MikTip]

I replaced my fan control module...



Now my fans go full high, with the a/c on, and stay there the entire time.

I asked...never got a reasonable good answer for...

[EuroxS4]

It sounds like you may have a defective coolant reservoir cap. The cap is designed to hold between 22 and 23 PSI. So nothing should go out through the cap until you are over those pressures. If it's blowing out of the cap but when you remove it there is no residual pressure that would indicate that either the cap isn't working properly or you have a substantial leak somewhere else.

No coolant leaks i am certain of that.All coolant hoses have been replaced.I dont see any visible leaks.I did notice that the resovoir cap does not have that final detent when closingat the end. Perhaps this is my issue.Luckily I have another b6 so i guess ill swap caps.


Confirmed Cap is defective.Thanks