MainePorsche

Guys,
Just back from a 2300 mile jaunt with son for hockey and surprise visit to Mom and Sis.
After about 1000 miles started it up on day 2 with a high pitched, 'water is boiling', sound from rear of engine. All systems running well - didn't pull airbox for further look/see - kept going with trip. Car ran flawlessly. Sound would diminish in intensity, but not frequency of 'squeal' with higher rpm at idle until absent at higher rpm - leads me to believe some leak at throttle plenum when vacuum is diminished as rpm is maxed. With airbox off sounds as if it is coming from under manifold. All topside vac lines without sound and sealed to destinations.
Will remove manifold and find it.
Any suggestions on where to key in on ?
Any BTDT's ?
Thanks in Advance.
Craig

WallyP

Get a 4' piece of small rubber or plastic tubing. Stick one end into your best ear, use the other end as an acoustic location device.

MainePorsche

Yes, this will be a good localizing maneuver while still attached and 'sounding'.
Thanks Wally.

Mongo

A split ISV hose can cause a stuck-pig squeal too. Happened to me.

MainePorsche

Yep, that was high on my differential.
Will 'pop the top' tomorrow.

MainePorsche

The ISV hoses were high on my differential, but first on my diff was the throttle body gaskets. On the medial aspect of both they were worn to almost nothing. Everything else looks fine.
Boy, I was in here not to long ago (about a year ?) and they were OK.
Phone call to Roger and the usual WYAIT stuff.

When you place new gaskets are they 'dry', or should one apply some sort of sealant there in addition ?

Mongo

I did mine dry. The ONLY thing you could use sealant on are the intake manifold gaskets. Don't put the sealant on the port areas, but a very light dab and spread, here and there in between will keep the gasket from moving when reinstalling the intake.

MainePorsche

Thanks Andy.

Bertrand Daoust

Craig,

When I replaced mine, I didn't use anything.
I like Andy's suggestion though.

Mongo

This was my largest fail when I did my service, well second largest. My first was putting on a defective ISV hose that had a slit in it, causing the loud squeal I mentioned at idle. The second was when I installed the gaskets, they slid around when mounting the intake despite the studs providing some support for mounting them. The second time around after fixing the hose hours later after the noise, I discovered the dab of RTV trick worked really well for keeping everything in its place.

Mrmerlin

when you set the intake base gaskets they should be laid onto the head surface,
the thrust collars should also be in place,
then the manifold is laid onto top of the gasket .
NOTE they should not need any type of sealant to locate them as they should all fall into place.

NOTE the gasket orientation is critical.

NOTE pay attention to where the manifold seats next to the base of the water bridge ,
if its cocked a bit,
then the edge of the manifold can catch on the water bridge and cause an unseat.

Always replace the two plastic hose attach fitting that press into the MAF boot as these will usually crack.
If your crafty (Ace has it)go to the hardware store and buy some brass tubing in the hobby section they have a size that will neatly press into the center of the inlets ,
a dab of super glue will hold them in place, this will stiffen the plastic.

MainePorsche

Thanks Stan.
I've been pretty good with manifold setting in the past.
Though my inlets to the MAF are not cracked, you're suggestion sounds great - an ounce of prevention will go a long way with this.

MainePorsche

Actually on closer inspection of the gaskets, the L was considerably more worn than the R to the point where air ingress occurred. Will carefully torque these on the new gaskets.

Mrmerlin

tighten the manifold evenly,
start from either middle nut,
then alternate left to right,
front to back,
till you reach the ends,
first snug them ,
then final torque the nuts

MainePorsche

^ Yes, that is exactly how I do it.
I was earlier referring to the throttle body gaskets - I wonder why one gasket was completely shot - though the 'good one' was close to death too.