Interesting Boost Leak Situation

[Chad989of2000]

Whilst I wait for the turbo to cool before I boost leak test the car, I wanted to run this by the pros. Just got the engine back into the car and everything hooked up, so I decided to start her. The car shakes violently then stalls. The only way I got it to hold an idle was to up the correction % via the Safc to +30. This allows the car to idle (albeit @ 2k rpm). Under the hood I can hear a very loud rushing (more so than a hissing) around the intake manifold, nearest the TB. I couldn't see any cracks or disconnected vac lines so I'm somewhat stumped. When the car is idling like this I do see 15 Hg of vac. I'm kind of stumped as to what is happening here. I plan to boost leak test shortly, but any advice would greatly be appreciated.

 

[turbowop]

You answered your own question. Do a boost leak test.

 

[Chad989of2000]

zing. snap. Was just fishing for some pointers...maybe key areas to look.

 

[Chad989of2000]

I also used a new intake mani gasket (oem Mitsu) upon reassembly.

 

[mikus]

Mark's right any input would be arbitrary at best. Do a boost leak test.

If you're not set up to do this in

 

[vtecds1]

Going to take a shot- Me and a couple of friends help out a local Chi-Town member last year. Had the same symptoms as you, and had to mess around with the AFC to get it to idle right or stay on. After dicking around for 2hrs...found out that the t-body gasket was on backwards.

 

[Chad989of2000]

Just did a boost leak test. Tested the whole system first...held no pressure. Tested the intake mani second, same...no pressure being held. I've seen this before when a leak is too large, the air escapes faster than you can build pressure (in my case with a mountain bike hand pump). So I hooked everything back up and used some carb cleaner on the suspect area. While spraying along the entire intake manifold gasket area the car would stutter and almost stall. So it looks like I'll be removing the entire intake mani and rechecking the gasket and sealing. It just blows my mind how a brand new oem gasket torqued down to spec is leaking so badly.

No other leaks were detected, I really sprayed down the tb area...I know how much of a problem that gasket can be. Fortunately mine is also brand new.

 

It is extremely common for the head mating surface of the intake manifold to warp. Most machine shops will plane it for 20-40 bucks. Take a straight edge and check it while you have it apart. Also look at the injector isolators (lower seals). I tore one when reassembling my engine a few months ago.

 

[Chad989of2000]

It's just weird because the car ran fine with no vac leaks before I removed the engine. I did nothing to the intake manifold save put a new gasket on. I hate taking it off and putting it back on...those lower bolts can blow me.

 

[gramkrakr89]

Removing the manifold for a new gasket sounds like something to me. /ubbthreads/images/graemlins/dunno.gif It's not that bad considering what else could be wrong... make sure you didn't crack the manifold while putting the engine in (seen/heard about it before).

 

[Chad989of2000]

Off to remove the intake manifold. I'll check for cracks while I have it off the car. Thanks for advising me to try a boost leak test.

 

[Chad989of2000]

Come to think of it...the car was running a paper Felpro gasket before...since I put a metal oem one in to replace it, maybe that's why I'm seeing this issue now. The metal seems like it may be more discriminatory to uneven or slightly warped surfaces. Hence why there was no leak with a paper gasket in place. Anyone try those plastic gaskets (phenolic)?

 

[rdomeck]

This sounds like my car after I reinstalled the engine....I had an injector seal leaking. I didn't have one of the injectors seated correctly. Might be worth pulling you fuel rail off and check to see that all the injectors are were they should be!

 

[omertaitalia]

Quoting Chad989of2000:
Come to think of it...the car was running a paper Felpro gasket before...since I put a metal oem one in to replace it, maybe that's why I'm seeing this issue now. The metal seems like it may be more discriminatory to uneven or slightly warped surfaces. Hence why there was no leak with a paper gasket in place. Anyone try those plastic gaskets (phenolic)?


my neighbor runs a phenolic, i want to go this route eventually, seems like a cost effective mod.

 

[Chad989of2000]

Quoting rdomeck:
This sounds like my car after I reinstalled the engine....I had an injector seal leaking. I didn't have one of the injectors seated correctly. Might be worth pulling you fuel rail off and check to see that all the injectors are were they should be!



I was hoping that it was that easy of a fix. When I checked with carb cleaner along the top of the intake mani, I got engine response from each top intake mani bolts and surrounding area, no hits around the injectors. The metal gasket was sealing fine at the bolt but was leaking on either side. It was just too thin to create an airtight seal. So I pulled off the entire intake manifold (hate those bottom 4 bolts) and am waiting on the new phenolic gasket I ordered. Plan to put a thin layer of RTV on each side and really lock that thing in. I am not putting this back together just to tear down again.

 

Why not fix the real problem?

You seem to agree that it is warped.

Take it to the machine shop and get that manifold surfaced.

Phenolic spacers are hard plastic. If they aren't (cause I've never had my hands on one), then they aren't actually phenolic.

Just to give you an example, phenolic is so hard that Ford produced brake calipers with phenolic pistons.

So if this spacer that you are buying is actually phenolic, you are going to need two gaskets with the spacer in the middle. RTV isn't going to cut it.

 

[mikus]

I've ran the "plasticky" spacers on two cars and would say you do NOT need a gasket, def. not RTV, for those. Don't know/care what they were made of, they worked fine & didn't melt at steady mid-20's PSIs

One was from Hondata, the other not sure but it was used enough where I was confident it was quality/wouldn't melt. The last thing you want is to have one melt and you go lean.

 

[Chad989of2000]

If I was going to get the intake mani planed I would also get the head planed where it connects to ensure a perfect fit. As far as warping goes, the paper gasket w/ no RTV on there before held airtight w/ 20psi boost all day. I think the metal gasket was just not up to snuff. I've also heard plenty of good criticism on the Phenolic gaskets...I'll slap it on and see. If it actually creates a temp difference...bonus points.