Hello, I am about the dive into replacing the Coolant Temp Sender O-Ring and the Coolant Bypass o-rings located in the back of the engine of a 1998 Audi A4 2.8L. The car sat for about 6 months and after I replaced the thermostat (the mechanic didn't replace the thermostat 3 years ago and it failed) a coolant leak started at the Temp Sending Unit and the o-ring on the driver side. I suspect the o-rings deteriorated since it sat so long. Since one o-ring is leaking, i might as well replace all of them (price of o-rings were cheap enough to do them all). I also bought a set of intake manifold gasket as it needs to be removed to get to the coolant bypass pipe. The task does not seem too hard just time consuming. My question is: Do I need to depressurize the fuel system to remove the intake manifold? I have seen on YT mechanics just taking the bolts off for the fuel rail and flipping it towards the windshield without depressurizing the fuel lines. Any help is appreciated. And Thanks in advance.

1998 Audi A4, 2.8L
John

Not if you are just pulling the rail with the injectors attached to it. I didn’t on my 1.8T.

Thanks for the reply.

John

+1

I've done it a dozen times.