OverPressurized Coolant System - JeepForum.com
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post #1 of 5 Old 07-16-2017, 06:50 PM Thread Starter
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OverPressurized Coolant System

So i just bought my first jeep from my boss. Now my 1998 jeep grand cherokee laredo (told its a wj) came with a few problems of her own.

Previous owner ran the engine till it overheated. Upon a small flush i discovered the coolant system was fully neglected. As well as every other maintenance (ex: oil change, rust prevention, etc). One word. rust.

So after thoroughly flushing the entire coolant system, replacing the water pump and thermostat. My jeep wasnt liking the idea of holding an idle at startup.

Ok so i knew it overheated, and now i know there is a cold idle. I figured its time to check for the possability of a blown head gasket. Well... Haha..

Engine pressure test came out fine. Coolant pressure test was lower then normal (over a period of 3 months up to now). I discovered the rad had a few leaks. Oil was just oil, nothing mixed.

So now i start the engine after my tests and drove around for a few hours, suddenly my rad cap has coolant shooti g out of it. Oh no. After inspecting my radcap with the engine running, coolant just kept blowing out from under the cap.

Ok, somethings def up under my head. But what could it be.

Well i did just about what everyone fears to do, i tore my head apart. (Side note i discovered my rad developed a huge hole in it, and my heater core is blocked up(have to save for another time)).

In attached pictures are the head. Head gasket "looks" fine. Head has no cracks, and cylinders look "fine".but wait.

Theres dropleta of coolant sitting on top of the cylinder heads. Hmmmmm.

Now im wondering if it was just the manifolds' gasket that was bad. Upon inspection the gasket "looks" fine.

Well to eliminate any doubt. Ill be sending my head out to a machine shop tomorrow to be cleaned, checked, and leveled. While thats out ill replace the rad and get a new manifold (due to my old one having cracked).

Ill post with any new info. And i hope i can help someone else with these symptoms.

Cyl: 6,4,3 (could be 1,3,4) has coolant/water presence. Cyl 6 (or 1) has rust and will need to be honed.

Attached Thumbnails
20170716_130404_Burst03_1500252300960.jpg   20170716_130415_Burst01_1500252340655.jpg   20170716_133758_1500252397605.jpg   20170716_130424_1500252465189.jpg   20170716_130429_1500252526528.jpg  

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post #2 of 5 Old 07-16-2017, 06:51 PM Thread Starter
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4x4 l6 4.0L
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post #3 of 5 Old 07-18-2017, 09:09 AM Thread Starter
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So yesterday i sent the head out to be checked and decked. No cracks, but the head was twelve thousandths of an inch warped. (What i was told).

I worry my engine block is warped or cracked now, but i really really dont feel like tearing it apart to remove.

I will have to find visual alternatives to find a crack (was exhaust into coolant system and slight coolant leak into cylinders) so at least i know where to look. And a good straight edge feeler gauge to check for a warped block.

Id really like to just magnaflux the block but yeah. Again. Dont wanna take apart everything.

Well now im at a loss. Any tips or info is appreciated
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post #4 of 5 Old 07-23-2017, 07:34 AM Thread Starter
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Well i put the engine back together. Gonna fill fluids and bypass heater core.

Replaced radiator.

Upon checking thermostat again i realised the previous owner had the thermostat in backwards. So i flipped it aroung (now spring towards engine).

New exhaust manifold. New seals all around top. Rocker cover seems to be sealed weird but its tight.

See pics for new exhaust manifold and a side by side of radiators. Will post with results later on.
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20170722_193504_1500816694989.jpg   20170722_153336_1500816841698.jpg  
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post #5 of 5 Old 07-23-2017, 05:15 PM Thread Starter
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After all this. Jeep runs like its new. Link to finish everything off.

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