1G FIAV Leaking boost into cooling system

[kchaazz]

First off, the problem here is the FIAV and only the FIAV, its been proven already to be the culprit, Im just trying to find out what within the FIAV assembly has failed and what to do about it.

So, I was performing a routine boost leak test on my car, and happened to notice that the coolant in the overflow was bubbling. Crap, I thought, headgasket is on its way out, so we did the following:

1. Compression test, resulting in 155psi across the board.
2. Leak down test, no negative results, coolant didnt rise, nor did any air bubbles manifest themselves.
3. Next, I checked the torque on my head studs, and they are good.

So, Im getting ready to pull the head anyway so that I can inspect the gasket for damage cause air blowing out into the coolant reservoir during a boost leak test HAS to be a headgasket issue, right? Wrong. Bogus SVO came over, and we decided to check the FIAV to see if it was somehow pissing the pressurized air into the cooling system. I pulled both coolant hoses off the nipples on the FIAV, pressurized the intake tract to 25PSI, and sure enough, the nipples were pissing air! Ive been around a good while, and I have never heard of this before.
So, is there anyone familiar enough with the components within the FIAV assmebly to tell me whats wrong with mine? Its amazing that this thing wasnt allowing coolant to be sucked into the motor under vacuum conditions, and the car runs great, no overheating, nothing, and if I hadnt been paying close attention when doing the BLT, Ida never noticed the problem.

Ive got lots of throttle bodies here at home, but I just dont want to put another FIAV on only to end up with the same problem....

 

[xxNocturnalxx]

Nice catch and good info.

 

[pneumo]

It's the seal between the FIAV and the bottom of the TB. I had a leak there just like yours, it pushed coolant only at high boost. I fixed it by looping the coolant lines at the TB.

 

[luv2rallye]

I'm not familiar with FIAV but this may help (or at least be interesting). Sounds like you may just need a new gasket (or loop the coolant lines like guy above said): http://www.dsmtuners.com/forums/articles-intake-exhaust/320951-fiav-adjustment-disable.html

 

[kchaazz]

Thanks, guys, that makes perfect sense. Ill order a new gasket and just loop the coolant hoses for now.

 

[kchaazz]

Update: So, I ordered a new FIAV gasket, cleaned both surfaces of the throttle body where the seals go, so clean they looked new, carefully put the TB back together, reinstalled the TB on the car and promptly performed the BLT. Bad news, the FIAV is still pissing air out of the coolant nipples, so I just looped the hoses again. Maybe after a few heat cycles the gasket will seal up?? My newish injector insulators leak like hell after I removed the fuel rail, so I will be putting in brand new ones tomorrow after work and Ill check the fiav when I do another BLT. Those damn insulators are just disposeable- every time Ive ever pulled the fuel rail, they leak like hell after, even if theyve only got a few hundred miles on em

 

[kchaazz]

Update: I pulled the throttle body off the car again. I said to myself, "Screw this, I'm not putting this thing back on til I verify that it absolutely is not leaking!"

Took a FIAV assembly off another throttle body, cleaned it up nicely, bolted it to my throttle body with the new "waffle" gasket, then put a short hose on one of the coolant nipples on this FIAV with a barbed fitting in it and an air chuck on the fitting. On the opposite nipple on the FIAV, I put a short piece of hose with a barbed fitting with a pipe cap on it. I then put a regulated, steady 40psi into the coolant chamber of the FIAV and sprayed soapy water into the air passages of the throttle body.

With my other FIAV bolted on, it sprayed and bubbled like crazy, but this one did not bubble at all. I then boiled a pot of water and put this FIAV into the pot and watched it work to be sure it is functional and after that I reassembled the TB and put it on the car and did the boost leak test again and checked the nipples for air pissing out just in case pressure from the "air" side of the FIAV would leak still. No leak, so I put the coolant hoses back on and boost leak tested once more and the coolant had no air bubbles pissing out of the filler neck with the cap off, so this is a success!!

Later, I will remove the leaking FIAV from the casing and attempt to figure out what exactly was causing air to get into the coolant side of things.

 

[BogusSVO]

Glad you got it fixed. You were quick to want to change the HG!!

 

[Tiki2777]

Whatever you do, you should still loop the coolant lines, because running hot liquid through your intake system is not good for keeping intake temps down and power up. Glad your FIAV no longer leaks though

 

[WES_393]

Whatever you do, you should still loop the coolant lines, because running hot liquid through your intake system is not good for keeping intake temps down and power up.

Not exactly. The FIAV is operated by coolant temperature, so just removing the lines and not properly eliminating the FIAV can cause issues.

 

[steve]

Not exactly. The FIAV is operated by coolant temperature, so just removing the lines and not properly eliminating the FIAV can cause issues.

Like too much bypass air causing to idle surge.

 

[kchaazz]

^^Indeed, the car was really running like shite when I did have the coolant lines looped. This was only a temporary solution in my case. Even after driving ten miles, the FIAV still wasn't hot enough to close and I would get insane Idle surge.

I'm back to stock driveability now though

 

[007jimmy]

You must be logged in to view this image or video.

You must be logged in to view this image or video.

You must be logged in to view this image or video.

You must be logged in to view this image or video.

I know this is a few years later but it's still basically the same issue with a slightly different twist, since the TB was rebuilt from a reputable source it was the last thing I looked at because I assumed everything was alright. So:

I was having very high idle at startup and sometimes it would surge for a few minutes (strangely it wasn't every cold startup). It would drop pretty quickly to 750 rpm and I would also get little "misses" which was random as well. When I did my BLT I got no signs of failure @30PSI. I had some smaller bubblers that I fixed but after restarting the car the idle was still high. I know the FIAV is basically mechanical so I was planning to pop the freeze plug and screw it shut. Here's what I found. I replaced the bottom half with another unit I had from a previous build. Car fires up just fine now and no more insane high idle at startup. I'm hoping this can save someone from potentially hydro locking their motor or whatever other issues this could lead to.

Just want to edit that the center gasket did not fail. Also the black screw was corroded shut so I couldn't turn it.

 

[MadSciHighPSI]

You must be logged in to view this image or video.

You must be logged in to view this image or video.

You must be logged in to view this image or video.

You must be logged in to view this image or video.

I know this is a few years later but it's still basically the same issue with a slightly different twist, since the TB was rebuilt from a reputable source it was the last thing I looked at because I assumed everything was alright. So:

I was having very high idle at startup and sometimes it would surge for a few minutes (strangely it wasn't every cold startup). It would drop pretty quickly to 750 rpm and I would also get little "misses" which was random as well. When I did my BLT I got no signs of failure @30PSI. I had some smaller bubblers that I fixed but after restarting the car the idle was still high. I know the FIAV is basically mechanical so I was planning to pop the freeze plug and screw it shut. Here's what I found. I replaced the bottom half with another unit I had from a previous build. Car fires up just fine now and no more insane high idle at startup. I'm hoping this can save someone from potentially hydro locking their motor or whatever other issues this could lead to.

Just want to edit that the center gasket did not fail. Also the black screw was corroded shut so I couldn't turn it.

After over 2 years of headaches chasing cooling issues, hoses, changing water pump, radiator (was bad), HG (not bad), more hoses and STILL having cooling issues I am trying this tonight and very hopeful.

Thank you for posting this here!