Ocasssonally cuts out (UrS4 auto)

[quattrokid2]

😳 erm.. I'm all

The fuel relay has also been advised to me, I'll get on the case a week Saturday when I see the car again 👍🍻

I also have a noise that sounds like a distant foghorn when I come off the throttle, even light throttle, sounds like a valve resonating air somewhere

When the turbo blew up on s previous time I owned the car... it ruptured both crankcase seals which where replaced.

How can I pressure test the crankcase to check that no pressure / vacuum is leaking ?

[newsh]

The fog horn could be the diaphragm split in the DV Pull the vac line off the front of the IM and suck on it, you should have vacuum.

A boost leak test with the PCV system still connected will test the crank case and PCV system. Max 1 Bar and be prepared to split a pipe if they're old and rotten. You may also blow oil past the turbo seals into the exhaust..

[UrS4boy]

Bluequattro, could you explain what a thermal fuse does please? Is it a circuit breaker between certain temperature conditions and snything above that temperature it opens ? Under normal conditions what's getting so hot that it opens a thermal fuse? What's it protecting ?

Thermal fuses are bimetal contacts that heat up and bend away from the contact points when the current is too high. They eventually cool down and the contacts retouch and the circuit is complete again. Sort of a multi-event reusable fuse.

A good visual investigation of this issue is available here:

https://picasaweb.google.com/117979369085854910207/AudiUrSS64IgnitionBreakerS72FuelInjectorBreaker?authuser=0&feat=directlink&gsessionid=O_Ji-3RrXASee0wFYQmSrA#

[quattrokid2]

Thanks newsh, I'll bear this in mind...

Urs4boy, why would this thermal fuse only open ocasssonally and could be minutes apart of in some cases months apart ? What current gets too high resulting in opening the circuit? Why not every time the engine is running of at least when the ignition is turned on?
(I'm a complete novice with electrical wiggy diagnostics 😢&#128563

[UrS4boy]

Urs4boy, why would this thermal fuse only open ocasssonally and could be minutes apart of in some cases months apart ? What current gets too high resulting in opening the circuit? Why not every time the engine is running of at least when the ignition is turned on?

Thermal fuses open/close based on load, i.e. current flowing through the fuse. They are never supposed to actually open, just take a bit more initial load than a normal spade fuse can handle and then carry on. As they age, they can start to forget what their brief was and might open earlier than they were supposed to and then, sometimes, forget to close again.

The solution, in this case, is to replace them with the same amperage normal spade fuses. If it cures your problem, you are done. If it doesn't cure your problem, then at least you know that those fuses are not the problem.

Intermittent electrical problems are a bit of nightmare but if you start to eliminate possible causes, you can narrow the source of the problem much quicker.

Buy a set of spade fuses and install them. Any aftermarket car parts supplier will have the spade fuses.

[quattrokid2]

Cheers fella, much appreciated

My Bruv in law has an S6 Avant so I'll see if we can get his out and go buy some replacement spade fuses 👍🍻🍻🍻