This issue has been extensively documented here by people like EcoMike but I thought I would do my own thread as I diagnose and repair mine. I have a 1990 Cherokee that had a 300K wonder of an engine. Always ran in the 190-200 degree range, occasionally spiking up to 210 going uphill on the freeway without the stock engine skid on. (More on that later). I have a winch and lights blocking airflow through the radiator. Rings were shot and it had blow by that required special plumbing to avoid it becoming some kind of Nazi extermination device. Compression was around 90-100 on each pot with one down around 75. Oil pressure was embarrassing but did not seem to bother the engine. The mill we all know and love. Never even thought about the cooling system. Had a 6 year old water pump and a plastic 1, or 2 row radiator from the middle ages. I hard wired the electric fan circuit for occasional use on the trail. It never overheated except the one time it blew a heater hose. Anyway I got tired of putting oil in it and gassing my passengers but it worked like a champ.
Fast forward:
Acquired a chrysler rebuilt Renix engine for $250 with 150K approx, since rebuild from a reliable source who told me that it had "ran fine" when pulled a year ago. It had sat in his shop for that time. He had it for sale before it was pulled and I had asked him for compression and oil pressure reports at the time. 135 psi each cylinder and great oil pressure. We could not agree on price. When he finally dropped the price to a fraction of what I had originally offered I figure "what is the worst thing that could happen" So I swapped over the engines after doing the requisite RMS install while the engine was out.
I did commit the cardinal sin of not flushing the engine cooling system out before running it which I regret. Will admit that now. I was more worried about whether or not the thing would actually run, that the valve seats would be rusted and pitted Run it did. It started on the very first crank great compression and oil pressure. (Love these engines).
So I have now been running the beast for a couple of months and the only issue I have with it is that it runs at about 210 at idle and regularly gets up to 225-230 under load. My engine skid no longer has any impact. My own theory here is that the engine skid works like a spoiler and will actually suck air through the rad. Manifolds, sensors, injectors are all off the old mill including temp sens. Now this is not necessarily bad but like EcoMike I want the cooling system to be the best it can and my wife complains that the engine "smells hot" ( I hate this) when going uphill on the freeway. I do think it is a little close to the ragged edge. Summers here are not horribly hot but I actually would like to take this rig to Moab at some point. BTW I am not interested in going to an open cooling system and am not going to debate that bit.
So working theories in order of likelihood imo:
1:I have clogged the rad up with stuff from an engine sitting for a year.
2: That an engine that actually has compression runs a little hotter and that the old cooling system is not up to the added requirements.
3: The POS Hayden fan clutch that I installed is not working.
4: Head gasket
5: Water pump/thermostat
6: Radiator tired
7:After reading EcoMike's saga air trapped in top of rad
My plan is to document my steps and report on the results.
Step 1: Thanks GoatMan, Perform exhaust gas detection test on cooling system: Passed
Step 2: flush the system: In process and will report.
Step 3: Inline filler neck: In process and will report
My plan is to go through the system and replace parts that are unknown to me. I will be installing a CFS 3 row radiator and a Hesco water pump,a robertshaw 180 deg stat and a ZJ HD clutch.
More to come
Fast forward:
Acquired a chrysler rebuilt Renix engine for $250 with 150K approx, since rebuild from a reliable source who told me that it had "ran fine" when pulled a year ago. It had sat in his shop for that time. He had it for sale before it was pulled and I had asked him for compression and oil pressure reports at the time. 135 psi each cylinder and great oil pressure. We could not agree on price. When he finally dropped the price to a fraction of what I had originally offered I figure "what is the worst thing that could happen" So I swapped over the engines after doing the requisite RMS install while the engine was out.
I did commit the cardinal sin of not flushing the engine cooling system out before running it which I regret. Will admit that now. I was more worried about whether or not the thing would actually run, that the valve seats would be rusted and pitted Run it did. It started on the very first crank great compression and oil pressure. (Love these engines).
So I have now been running the beast for a couple of months and the only issue I have with it is that it runs at about 210 at idle and regularly gets up to 225-230 under load. My engine skid no longer has any impact. My own theory here is that the engine skid works like a spoiler and will actually suck air through the rad. Manifolds, sensors, injectors are all off the old mill including temp sens. Now this is not necessarily bad but like EcoMike I want the cooling system to be the best it can and my wife complains that the engine "smells hot" ( I hate this) when going uphill on the freeway. I do think it is a little close to the ragged edge. Summers here are not horribly hot but I actually would like to take this rig to Moab at some point. BTW I am not interested in going to an open cooling system and am not going to debate that bit.
So working theories in order of likelihood imo:
1:I have clogged the rad up with stuff from an engine sitting for a year.
2: That an engine that actually has compression runs a little hotter and that the old cooling system is not up to the added requirements.
3: The POS Hayden fan clutch that I installed is not working.
4: Head gasket
5: Water pump/thermostat
6: Radiator tired
7:After reading EcoMike's saga air trapped in top of rad
My plan is to document my steps and report on the results.
Step 1: Thanks GoatMan, Perform exhaust gas detection test on cooling system: Passed
Step 2: flush the system: In process and will report.
Step 3: Inline filler neck: In process and will report
My plan is to go through the system and replace parts that are unknown to me. I will be installing a CFS 3 row radiator and a Hesco water pump,a robertshaw 180 deg stat and a ZJ HD clutch.
More to come