And the "Hissing" sound goes on.....

[speedy1320]

This problem is not diagnosable for me! I have removed, replaced and checked all the IC hoses but cannot find a BOOST RELATED HISS I get when under acceleration.

I could SWEAR it was an IC hose that "squirmed" off.....but that's NOT it.

I checked my IC....it's TIGHT !

This happened AFTER my car was at a shop getting timing chain/gears/waterpump/oil pump replacement. {68K miles}

It runs well.....but NOT as fast as before....which REALLY pisses me off after spending $$$$$

I cannot see any vacuum line issues either....but since it's only under boost......I wouldn't think it could be a vacuum line.

Suggestions?

Thanx!

Tom

87 WE-4
3"DP, 3" Cat, ATR exhaust
Adj WG Adj. FPR
Testa chip
160 Therm
14" KN
Stretch IC
Green stripes
Walbro
Hot Wire

 

[TRENT THOMPSON]

justa first thought in my thick skull. make sure your PCV is pushed all the way in the intake

 

[KENNE-BILL]

Perhaps the intercooler itself has a leak? Since it had to removed by the shop to get at the front of the motor, I would check for visual signs of damage to the core and pressure test for leaks.

 

[speedy1320]

Good Ideas guys........but as i said the IC is TIGHT, tested OK.....that was the first thought with the IC hoses.

The PCV was also something I looked at immediately......No Cigar!

Keep em comin..... This Sh** is driving me to DRINK........MORE !


Tom

 

[GNandTTA]

If you have an air compressor and leak down tester you could pressurize the entire intake area from the maf to the valves. Thats how I found my vacume leak (EGR gasket). Get a plastic 3" PVC plumbing plug and install an air hose fitting. Get some soapy water and start spraying. If you see bubbles you found a leak. I found a few other leaks but the EGR was a big one. Was not able to find using other tests.

 

[John Larkin]

How much boost does it take to make the sound happen? If not much, you could have someone powerbrake the car and you stand by the engine compartment, looking and listening.
Also, since they did the front cover, maybe the cam sensor is in wrong, causing lower performance. It happens.....

 

[speedy1320]

John......the cam sensor is something of great question to me! This could be suspect just because the car fires up slowly. {What I mean here is that the car turns over like 3-5 times before starting.}

I ordered a cam sensor tool and got it yesterday from Kirban. {Seems like a pain in the A** to do with the crank positioning, but we will see}

To answer your question.....the "HISSS" comes on as soon as boost is registered. And the more boost, the more hiss......

So you see.....I thought FOR SURE it was either an IC hose or the IC itself!!!!

Oh, one more thing.....{regarding cam sensor} when I got the car back from the shop......it didn't run as well.... in fact, I lost horse Power IMO.

But here again, I thought the cam sensor was NOT a timing device and only used for initial start up of the engine. How could this affect performance?


The PCV idea is a good one! I have also thought about "Power braking" the car with a friend.....dangerous though.

Where are you suggesting to apply air too? The PCV inlet, or the LIne going out?

Thanks guys......I'll get to the bottom of this!@

Tom

 

[gn1220]

I think GNandTTA is saying to blow air into the motor through the MAF pipe, hence the 3'' plug with the air chuck. Make sure you open the throttle blade.

 

[gndeligirl]

Hi I had a similar sound loud hissing at boost also. this happened one night after making some quarter mile passes. It was an exuast leak. I had one of those poston two piece crossover pipe that blew out causing major hissing at boost. The exuast leak wasnt that loud at idle.

 

[speedy1320]

So GN1220.......if I am understanding you and Gntta....You are suggesting applying air pressure to the BLOCK through the PCV Port in the intake??? I mean, it makes sense to pressurize the block and thereby pressurize the throttle body, downpipe, IC etc....... {with Blade open of course} but what is a "safe" amount of air pressure to use here.......15lbs, like in a Boost scenario?


Gndliegirl...... I thought about a possible exhaust leakalso... Let me ask YOU a question........how did you actually FIND it?? I have looked at the factory exhaust manifolds......which I hear are prone to cracking......but cannot SEE anything. Any ideas to further help in finding a small crack?


Thanks again


Tom

 

[gn1220]

I can't speak for GNandTTA but I would guess he is saying to blow air through the MAF pipe to simulate air going into the engine, not the PVC. That is probably why you need a 3'' PLASTIC (PVC like for water pipes in a house, not the Positive Crankcase Ventilation Valve in the car) cap with an air chuck in the middle. Remove the MAF, put this PLASTIC cap in the end of the MAF Pipe, (secure with a clamp or whatever) and fill the motor with air. GNandTTA, is this correct?

 

[GNandTTA]

Yes, pressurize through the MAF (3" PVC plug). Just make sure you have some type of pressure regulator on the air line. I used my leak down tester but someone else may have a cheaper way. I would imagine you could probably break something if you were to put a full 100 + psi through the motor!! Once it's pressurized, start spraying the soapy water. You would be amazed at the amount of leaks you will find.

 

[Quick89]

Hissing

You don't have a bleed off valve on the car do you??? Some hiss really loud under boost

 

[gndeligirl]

Hissing, my exuast leak was at the slip joint of the crossover pipe under boost it would open and hiss louder than you could imagine. Check all your flange connections and driver side manifold. Like I said at idle the leak wasnt that apparent. Good luck.

 

[Outpost]

We experienced a similar problem in our car and identified the source of the noise by having my wife powerbrake the car just a bit while I stood along side it. It turned out to be the turbo causing the noise - the centershaft was untrue and the turbine was contacting the side of the housing. We still don't fully understand what caused this to occur. If you run this same test, be sure to dive into the nearby bushes (like I did) when the tires begin to smoke.