Very odd coolant problem

orodi · Jun 1, 2010

So my brother in law just bought a 94 Gt, If you drive it normally down the road nothing happens, If you floor it the coolant sprays out of the overflow bottle. The cooland was brown so. I did head gaskets. I didn't see anything that was obviously wrong with them which was the odd part. I used P9333 when I changed them and now it is doing it again? I did a compression test everything checks out. If you just drive it everything is fine temp, oil presssure everything. When you floor it all gauges are fine, doesn't break up at any RPM level. My best guess is either a cracked head or crack in the block. Any thoughts?

Lee12609 · Jun 1, 2010

do a pressure test. if it was a cracked head or cylinder you'd be seeing plenty of exhaust steam/smoke....

orodi · Jun 1, 2010

It bleeds off pleasure, no steam or smoke.

CC'S95GT · Jun 1, 2010

With the rad cap off. have you watched for bubbles in the coolant?
napa sells a kit to detect exhaust gas in the coolant.

ivan12 · Jun 1, 2010

You most likely have exhaust going to the coolant, I have the same problem.

orodi · Jun 1, 2010

Ok so what do you do to fix exhaust in the coolant? I am not seening how that happens but it seems like the right fit for the symptoms. I checked the deck height on both the block and the heads and there were no low spots. Is the exhaust thing a common problem?

ivan12 · Jun 1, 2010

It could be as simple as a head gasket or as hard as having to have a shop remachine your stock heads and or block, which in that case it might be cheaper to look for a replacement short block. My .02 from experience, I spent $300 to have my heads milled and a valve job plus around $120 in gaskets plus a couple other things that nickled and dimed me. Wasn't worth it in the end, plus I still have exhaust coming into my coolant leading me to believe that there is something wrong with the block. BTW I replaced my rad and water pump with the same results.

LAFENATU · Jun 1, 2010

Did you do a leakdown test as well?

orodi · Jun 1, 2010

Wow that sucks. I didn't want to have to replace the motor for him but oh well.

ivan12 · Jun 1, 2010

I'm not saying you have to, first do all the tests. Engine swap should be kind of a last resort, but at the price some of these short blocks come up sometimes it's cheaper on the long run.

orodi · Jun 1, 2010

Yeah I plan on doing everything I can but if it comes down to it I'll just drop in another 5.0L I found one already that was $675 intake to pan. He's not modding it for a long time, since he is starting college in the fall. I just want to make it run right for now.

MustangMoser · Jun 1, 2010

simple check for exhaust getting into the coolant system....start with the car cold, run it for a minute, dont allow it to warm up, and pull off the radiator cap, there shouldnt be any pressure on it. another trick, put shop air into the cylinders and see if you're getting any bubbles in the coolant. or, use a leak down tester. it could just be as simple as a clogged radiator causing a lot of pressure build up. in my experiance a cracked head, or block will leak exhaust into the coolant system as bad at idle as at higher loads. this one may be different though.

orodi · Jun 2, 2010

I'm borrowing leak down testing equip. from a buddy at a shop tomorrow. I have never heard of a Fox body doing this, freaking weird. I know it's almost the same power train as the SN95 but holy are there some screwy problems with these cars haha.

MustangMoser · Jun 2, 2010

Screw a fox body. lol

MustangMoser · Jun 2, 2010

At least an SN car doesnt look like a friggin shoe box comin down the road

Lee12609 · Jun 2, 2010

I agree with mustangmoser, even a hairline crack would cause problems during normal driving. I would be looking for a restriction in the cooling system. Should hold pressure with a pressure tester though.

orodi · Jun 2, 2010

Well, ha ha I figured it out, the exhaust in the coolant was fixed with the head gasket change....It was coming out of the small tube next the where the upper radiator hose mounts on the lower manifold. It's aftermarket chrome piece and that tube THREADS in so it was loose and had no sealant on it. Even though it was a colossally stupid thing to do, I put the rear of the car on blocks and had him drive it and it sprayed every where when you put it under a load. It dripped when sitting there but I couldn't see it leaking. Problem solved, I beat the piss out of it for 3/4 of a tank of fuel and nothing.