SCARY COOLANT LEAK

Ok, Tell me this is OK and all I need to do is seal the thread.....

Just got my SECOND engine back from the shop (long story). Has about 100 miles on it, running great. I just noticed a small coolant leak coming from the front exhaust stud on the exhasut manifold. I don't want to believe the head is cracked......

AH not good I'm guessing this is a 4.0. The only engine that I know of that the exhaust manifold bolt goes all the way through to the coolant is the Dodge 360 v8 from the early 90's. Im not and engine expert but I would think that is really bad.

Year?

Yep 4.0.

I have a bad feeling.

make sure it is not spraying from the lower rad hose and if not, your fears are confirmed. No coolant should be in the exhaust manifold. You could try to re-torque the head bolts.....that might fix it????

Checked that first. Definately oozing out the front stud of the manifold. Out the thread, and around the nut.

Nevada City Sparky said:

Just got my SECOND engine back from the shop (long story).

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It sounds like we need to find out the story from here first before telling you to take it back to the shop!

Run it over to the shop that did your motor if you can, have them look at it.. But i think you got trouble with this leak

when i got my '88, that front stud was altogether missing. no coolant was leaving the head through that hole. that definitely sounds bad.

From what I've heard from friends' engine shop experiences (horror stories), the mechanic may have lost that stud bolt and replaced it with a similar yet longer bolt and tightened it in to a point of cracking or breaking through to the coolant where otherwise the thread is not drilled and tapped all the way and normaly sealed! This IMO is especially easy with aluminum. I'd take it back to the shop and insist on observing the mechanic finding the problem. If you don't, they can find the problem and hide the fact it was their fault and make it look like it was your fault somehow. Or they may assume you know nothing about engines and tell you it is normal for rebuilt engines to do that. If they do say that, I would really be suspecious of their workmanship and honesty. Then report to BBB! I am no expert as there are some here, I hope someone here can help with an easy fix if no resolve is found at the shop. Good luck!

Sounds like cracked head... sorry man.

You would have probably saved considerable time and headache by just doing the rebuild yourself... Seriously I recently did a head swap and I remember explicitly that it is a "blind hole". The early 4.0s had an ordinary bolt there instead of the stud... Joe

I DIS-agree on the "early 4.0s had an ordinary bolt there instead of the stud..." as I have owned 2 4.0 XJ's new since 1987 and 1988. Neither one has a bolt in the end of the exhaust manifold, on either end. I have, however, had the "experience" of having to replace one of the said studs, due to it snapping off during tear-down for re-build.

My 95 has a bolt for the exhaust manifold on the front side of the engine. Didn't look at the rest lol.

Fawk.

Here's the story:

1st engine, suspicious rebuild by shop. Was sent back for another rebuild.

Just got through putting second engine in, being as meticulous as possible. As a final check, I gave the jeep to my wife's friend's hsuband, who works at a dealership. Idea was he'd check it out and take it into the shop to scope it and ensure all was OK.

Meanwhile, I went on a business trip for a week.

I talk to him on the phone when I get back and according to him on phone call, all was perfect and he merely tightened a few bolts here and there. He offered to recharge A/C and we'd meet for dinner Friday night and he'd drive the 25 miles there.

Get to the restraunt and meet him and he tells me the jeep overheated on the way up. I especially had a bad feeling when he told me he didn't notice until it affected performance. He pulled it over and parked it and came on with wife who was in chase car. He said it didn't overheat until he pulled over, at which point the cap came apart on him.

So during dinner I find out he did nothing during the week he had the vehicle except drive it to and from work. I suspect at minimum he at least topped of the reservoir level and over-tightened the cap.

No doubt it's at least a blown head gasket, since I saw water drip ot the tail pipe on startup and the humidity is at 5% right now...

This just plain sucks. Two seasons missed now for 4x4, since I leave to work in Europe again in 3 weeks.

ren said:

I DIS-agree on the "early 4.0s had an ordinary bolt there instead of the stud..." as I have owned 2 4.0 XJ's new since 1987 and 1988. Neither one has a bolt in the end of the exhaust manifold, on either end. I have, however, had the "experience" of having to replace one of the said studs, due to it snapping off during tear-down for re-build.

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I will post a photo tomorrow.

Joe

well, mine had a stud, as did others I've seen.

Not that that makes much of a difference.... I'm screwed.

OK, I finally got a chance to do some testing yesterday. First of all, here is the leaking exhaust stud. You can see how the centerlines for the Head bolt and the exhaust stud line up:


Here's a closeup of the stud with the engine cold (these were cropped from an iPhone image, so sorry on the detail):

Notice the crusties from coolant leak last time it was driven...

Here it is after warm up. You can clearly see green coolant leaking from around the stud and washer. No leakage at all at the #11 head bolt (there is a white hazy material which I assume is sealant from when the shop assembled head and block):


Here's test results:

I did a cold compression check with all plugs removed and came up with:

138, 142, 145, 145, 145, 138, 138

A bit low on 1, 4, and 5.. but I'm thinking that's consistant with an engine that's gotten warm. I plan on retorquing.

Checked all spark plugs and everything looks good. All plugs firing cleanly.

Idles and runs nice.
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So, it doesn't appear as though there's a crack into the compustion chamber. If anything, I suspect there's a crack from exhaust stud hole to head bolt hole (or maybe it's drilled through?).

Here's what I'm planning to do:
1. Pull stud.
2. Examine best I can to see if crack or hole drilled through.
3. Seal with Locktite high temp thread sealant (same as used for Head Bolt 11).

I'm thinking I may want to pull the #11 bolt and reseal as well. Can I do this without loosening others?

Any other tips?

apply a teflon sealant to the left front head bolt threads. thats the problem. there is a water jacket that the bolt goes through

You'd have to use something for high temps, I assume.

If that's true about the water jacket, I suppose you're in luck!

Nevada City Sparky said:

Here's test results:
I did a cold compression check with all plugs removed and came up with:
138, 142, 145, 145, 145, 138, 138
A bit low on 1, 4, and 5.. but I'm thinking that's consistant with an engine that's gotten warm. I plan on retorquing.

Click to expand...

can you clarify those test results again please? I'm not so sure you have a 7 cylinder engine, right? so, which test results are which? and which cylinders are low? 1, 5, 6?