LOUD sound

[Suuperman]

'88 MJ 2.5L TBI without A/C.

 

Had a bad exhaust/intake gasket so I replaced that and went ahead and put in a new exhaust manifold. It was making a very loud noise that we thought was just a major exhaust leak and possible vacuum leaking as the gasket was broken in 2 pieces with part of it around the #4 intake port.

 

Cranked it up just now and the noise is still there...definitely not an exhaust leak.

 

Truck runs great...doesn't miss, no high/low idle and it revs fine when you give it gas with no hesitation or stumbles/backfires.

 

Sounds almost as if it is blowing air or sucking VERY loudly...actually sounds like one of those fireworks you set off on the ground and it spins around until it takes off...but the sound cycle is not quite that fast. When you give it gas and the RPMs climb it all but goes away but as the RPMs come back down it gets noisy again. When you turn it off you can hear it go FFFFF FFFFFFF as if it is puffing a last little bit of air.

 

Coolant appears to have no oil in it and vice-versa. I would think it it had a head gasket that bad it would not run as well or it would smoke...it does not.

[ComancheKid45]

Definently sounds like a vaccum leak.

 

Something should be noticable if the sound is that loud... :thumbsup:

[Suuperman]

We are now fairly certain is is indeed the head gasket. We did a compression check and the noise is coming from the #1 cylinder which only has 60# while #2 is 140+ and 3/4 are at 120 each. So it would seem #1 is bleeding into #2 causing the noise and the lower compression on 1 and higher on 2.

 

So now to pull the head and then hope the head isn't warped and replace the head gasket.

 

yay.

 

On a positive note it is running fine again...I think I got one of the sensors wet or something.