This is regarding this Jeep [urlhttp://www.bobistheoilguy.com/forums/ubbthreads.php/topics/3719586/Hard_grit_/_chunks_in_oil?__Pl]Here[/url].
The hard, gritty substance that plugged the oil pickup (along with sludge in a lot of places) was said to have indicated a severe overheat.
When looking in the engine bay of the Jeep, one could tell that the head had been replaced recently.
After cleaning out the oil pump , once the Jeep would get up to temperature, it would hemorrhage oil. We're talking 1 quart every 20 miles once it was warmed up. Replaced a few things - dizzy seal, oil pump seal, oil pressure sensor seal (that someone didn't even screw in all the way ...) and it started to leak worse.
Turns out it was all coming from the head gasket. Not uncommon for 4.0Ls of this era to leak from the head gasket. We had assumed that the previous owner overheated it and cracked or wapred the original head and swapped with the cheapest head gasket possible, causing the external oil leak.
Well ... we were close, but missing one fact.
It appears THEY REUSED THE HEAD GASKET. What?!?! Yes!
Ran a compression test on it and the only cylinder with good compression was 4. The other five cylinders were all at 50PSI. Can't remember what 4 was at, but it was acceptable.
When the head came off, this is what we found:
- There was no head gasket between 5 and 6 and 1/2/3. Appears that when the head was taken off, the PO scraped the material and just stuck the gasket back on
- Cyl 5 and 6 were dumping exhaust gas into the lifter galley
- The back part of te head gasket was missing, significantly, around the oil passages (hence major leak)
- There are coolant passages between the head and block that are SUPPOSED TO BE BLOCKED BY THE GASKET ... the PO drilled these out
- Numerous spots the gasket was just "missing" between coolant and oil passages
- Head coolant passages were filled with sludge and ,in a few cases, plugged.
With that said - this is why the AMC 4.0 has such a good reputation. It's still quiet (no knocks - even though it was run with no oil when the pump plugged) and has decent low end torque.
We also threw a timing chain at it since there was so much slack the distributor was 10* off. I suspect this is why the engine would run out of breath above 2500RPM. The head gasket, or lack thereof, was probably why it felt a bit down on power too.
I unplugged the coolant passages in the head. Hopefully that will stop the head from seeming to be extremely warm along with the valvecover. I'm sure a new head would do it wonders ... but the Jeep may not be worth it.
Has anyone else ever seen this before? I'm assuming that it was just someone trying to get the vehicle to the point that it would look good to sell.
It isn't back together. Still waiting for that.
I'm interested to see what the compression is going to be.
The hard, gritty substance that plugged the oil pickup (along with sludge in a lot of places) was said to have indicated a severe overheat.
When looking in the engine bay of the Jeep, one could tell that the head had been replaced recently.
After cleaning out the oil pump , once the Jeep would get up to temperature, it would hemorrhage oil. We're talking 1 quart every 20 miles once it was warmed up. Replaced a few things - dizzy seal, oil pump seal, oil pressure sensor seal (that someone didn't even screw in all the way ...) and it started to leak worse.
Turns out it was all coming from the head gasket. Not uncommon for 4.0Ls of this era to leak from the head gasket. We had assumed that the previous owner overheated it and cracked or wapred the original head and swapped with the cheapest head gasket possible, causing the external oil leak.
Well ... we were close, but missing one fact.
It appears THEY REUSED THE HEAD GASKET. What?!?! Yes!
Ran a compression test on it and the only cylinder with good compression was 4. The other five cylinders were all at 50PSI. Can't remember what 4 was at, but it was acceptable.
When the head came off, this is what we found:
- There was no head gasket between 5 and 6 and 1/2/3. Appears that when the head was taken off, the PO scraped the material and just stuck the gasket back on
- Cyl 5 and 6 were dumping exhaust gas into the lifter galley
- The back part of te head gasket was missing, significantly, around the oil passages (hence major leak)
- There are coolant passages between the head and block that are SUPPOSED TO BE BLOCKED BY THE GASKET ... the PO drilled these out
- Numerous spots the gasket was just "missing" between coolant and oil passages
- Head coolant passages were filled with sludge and ,in a few cases, plugged.
With that said - this is why the AMC 4.0 has such a good reputation. It's still quiet (no knocks - even though it was run with no oil when the pump plugged) and has decent low end torque.
We also threw a timing chain at it since there was so much slack the distributor was 10* off. I suspect this is why the engine would run out of breath above 2500RPM. The head gasket, or lack thereof, was probably why it felt a bit down on power too.
I unplugged the coolant passages in the head. Hopefully that will stop the head from seeming to be extremely warm along with the valvecover. I'm sure a new head would do it wonders ... but the Jeep may not be worth it.
Has anyone else ever seen this before? I'm assuming that it was just someone trying to get the vehicle to the point that it would look good to sell.
It isn't back together. Still waiting for that.
I'm interested to see what the compression is going to be.
