My 93 FD has all the classic symptoms of a vacuum leak, so I pressurized the system this morning. I put pressure on the elbow in to the throttle body. As I suspected it would not hold pressure. (This is correct thinking is it not? That it should hold pressure from the TB on to the engine.)

The leak is big enough that even with very low pressure I could audibly hear it hissing.
The bad news is that it is down near the turbos. Which sucks, because I was just in there and could have fixed it at the time. Oh well.

I am suspecting a bad lower manifold gasket, any other opinions? The engine was rebuilt in the last 10k, so I am kind of surprised that the manifold gasket would go already.

Any other place to look? Once I dig in to it, obviously I will find it, but just wondering of there are any common fail points.

 

Ok, update. The leak is somewhere around the UIM. I think it is under the UIM, but I am not sure.
The boost pressure tank on top has a very small leak. But, I don't think it is the main source. I have removed the UIM, but I don't see anywhere that could be possibly leaking, at least not visually. All the hoses were replaced with silicone a little over a year ago, and they are all ziptied.

On another note, while I had the UIM off I blocked off the AWS, just trying to simplify things.

Any ideas of where to look for the leak? The UIM gasket is new, as is the TB gasket and the rubber Oring at the elbow to TB.

HELP!

 

when you pressurize it, spray around with soapy water and see where it bubbles.

 

Yea, that's what I am doing in fact. Thats' how I found the small leak on the pressure tank.

 

Check the air control valve and your AWS block off plates - those can easily be leaks. Also, make sure the vacuum lines going to the front and back of the UIM are all connected.

Dale

 

i have the same problem

 

Dale, thanks. I will check the ACV. I just put the AWS plates on, so they werent' the leak. (although they could leak now lol).

 

take all the hoses off in the rats nest one by one and zip tie them with fresh zip ties. i had this same problem. One of my silicone hoses was very slighty loose. Good luck

 

2rotors, man, what a PIA. But, I will give it a shot

 

I wish there was some way to pressure the rat's nest with the UIM off. It would make it much easier to find the leak.

 

good luck

 

This is turning out to be a beast. Yesterday I found some leaks, and managed to strip a manifold stud.
I am having trouble getting the intercooler hoses to seal well. I have the worm type hose clamps and I can't get them tight enough. Any suggestions on a high quality replacement?
Also, right underneath the TB and the elbow, there is a small plastic tube like tank with a small air hose on one end and a larger one on the other, it is leaking air. I think it is the larger hose leaking. It has a factory spring clamp on one end, and I am going to replace that with a screw type clamp.