500, 472, 425, 368 Discussion, 425 Intake Manifold Removal in Cadillac Engine Technical Discussion; I have a vacuum leak that I beleive is coming from the intake manifold. Looking at the servive manual it ...
I have a vacuum leak that I beleive is coming from the intake manifold. Looking at the servive manual it appears that the coolant does not need to be drained first. Is that the case? To make sure its the manifold that is leaking, I am going to spray wd40 along where the manifold bolts to the head. The leak is very bad when cold and lessens at operating temprature.
I would look to see if any bolts are loose first an try tighten the first... There are not any coolant passages in the intake..
I checked and a couple of bolts were kinda loose. I torqued (tightened) the manifold and there was some improvement. As the motor heats up, the vacuum leak lessens. The motor runs smoother and the vacuum modulator on the trans starts to work properly. This problem started during a 1000 mile road trip. It was running great, then it wasn't.