Coolant leaking from exhaust bolt (Page 1/1)
Blitz54 OCT 04, 08:55 PM
Went to fix my exhaust leak this weekend on my 2.8. Turns out the manifold did have cracks on it, and the passenger firewall side gasket was getting blown by. Discovered another problem though. The same port, lower manifold stud leaks coolant. Had to pull the stud out to wiggle the manifold off, and as soon as the stud came out coolant started draining from the bolt hole. Went to thread it back in the next day (I just let it drain) and I'm only catching maybe two threads max near the back. Couldn't really see how the threads look as the coolant pipe is in the way.

Anyone else experience this? I took a pick and could feel some threads in there, but I could push the bolt in and out without much resistance. Almost like the threads are oversized. I guess I'll have to helicoil it? And put some thread locker so coolant can't get by it. I'll look at it next weekend, but hopefully the hole is at the end, and not on the size somewhere because that could make my helicoil not work I think.
Blacktree OCT 04, 09:10 PM
Coolant shouldn't be coming out of the exhaust manifold bolt holes. Those bolt holes don't go into the coolant passages. Sounds like the cylinder head is damaged.
theogre OCT 04, 10:40 PM

quote
Originally posted by Blitz54:
Went to fix my exhaust leak this weekend on my 2.8. Turns out the manifold did have cracks on it, and the passenger firewall side gasket was getting blown by. Discovered another problem though. The same port, lower manifold stud leaks coolant. Had to pull the stud out to wiggle the manifold off, and as soon as the stud came out coolant started draining from the bolt hole. {snip}

Head is dead and sad news likely is because someone installed the exhaust studs wrong.

This is a common problem people replacing OE hardware w/o a clue.

Why?
Short version...
Studs bottoming cranks or breaks the casting at install time, later as gets heat cycled, or both.
1. Stud metal is different from cast iron/steel or aluminum and expanse/shrink at different rates and "hammers" the hole bottom.
2. Hole threads often not made by a "bottoming" tap so threads are not uniform near bottom and studs, or longer bolts, can wedge the hole and put huge forces to try to split the casting. Related Note: Same can happen w/ sensors etc using tapered pipe threads breaking whatever when fools over torque the sensor. Very common w/ sensors in aluminum parts.

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

[This message has been edited by theogre (edited 10-04-2020).]

Blitz54 OCT 04, 10:56 PM
My question is, is it salvageable the way it is? As long as it lasts until taken apart kind of thing. It was running fine, and the coolant and oil were fine as well. Nothing mixing. I only removed the stud because of the exhaust leak. I have a 3.4 sitting, but not ready to be put in just yet.
theogre OCT 05, 12:14 AM
Get another head or swap engines.
Very likely even a full machine shop can't fix it. If they do will cost a lot.

Exhaust parts gets too hot to "glue" them even to seal treads.

1 broken hole leaking coolant is likely just a start. Other holes likely have problem and could fail next day.