So I re-wired my 1974 Jeep CJ5 over Easter weekend. Part of that re-wire included Autometer guages, one of which was coolant temp. I have been driving around since then with the temps being about 220-240F, which according to the service manual I have is the upper part of the operating range. The part that made me worried is that on the highway, I set at 230-240F. To me, on the highway it should be the coolest with all that airflow.
So I decided to dig into the cooling system this weekend and so far have tried the following:
1) Install new 195F thermostat with a 1/8" hole drilled to help burp the air out of the system. I tried my best to get the air out and went for a ride and it still acted the same.
2) Remove the thermostat all together and try to burp the system. When driving around, coolant was 180-200F. At idle, it would creep up to 210 or so, and that is when I shut it off. I should mention, the idle is set high in the Jeep right now. I am not sure exactly what RPM, but the oil pressure is 50psi, same as when going down the road or highway, so I know it is pretty high. I don't have a shroud or the HD radiator, so I just assume the radiator can't handle that load without a shroud to help pull air through the radiator. I am ok with this and will address the idle at some other point.
Now, what do I do about my cooling system. Do I still need to flush the system/radiator, or does the fact it runs 180-200F with no thermostat mean the system isn't plugged? I still feel there may be some air in the system,but don't know how to get the rest out. One more note, I do not have the heater core hooked up, but instead have a hose routed from the water pump the thermostat housing.
once you get the coolant system figured out. I would suggest going to a pick and pull and finding a ford taurus and pulling the electric fan. I got one to go with a 360 and the whole set up cost about 65 dollars the majority of that being the fan control from the autoparts store. It makes a huge difference and gives you a lot more control over cooling power than the clutch driven fan. The control i got can be set to cut on in a range of about 30* i think. I used to run at around 210-220 with the stock fan and now the highest i have seen it creep to was 212 at a stop in the summer.
I think the oil pressure is a clue to your heat problem. Oil not only lubricates but also helps cool the engine. High oil pressure can indicate a blockage of sorts preventing the oil from fully lubricating (and cooling) internal parts. If the pressure is the same at idle as it is on the highway at higher RPM's, this could indicate a worn relief valve and and sludged oil passages. The trickling sound you here when you shut it off may be oil running back down to the oil pan.
The oil pressure is high at idle because the idle speed is set high. If I shift into 3rd gear while at low speed, the engine RPM's will be brought down and the oil pressure will go to ~25psi. I mentioned the oil pressure just to give a clue as to roughly what the idle speed is at since I do not have a tachometer.
I have a separate ground strip under the dash that anything dash related gets grounded to. I can check that, but I feel the guage is reading correctly since it runs cooler without a thermostat. I can check this as it is an easy one to try.
50 psi oil pressure is great. i have a 350 sbc in my old willys jeep and it idles at 50 - 60 and will run at 70 - 80 psi. usually when your motor runs hot your oil pressure will drop, the hotter the oil gets the lower the pressure. id try another gauge, if you can find even a cheap one, just to make sure the gauge isnt the problem. it seems like you have checked everything else. then id have the radiator checked out. you should be able to get a radiator for under $200.00 from autozone or checker, or check ebay. the only other thing i can think of is a bad vacuum leak, that would lean the motor out and cause it to run hot.
Just a thought, i've been watching the same thing with my 258, tried all kinds of things trying to solve the problem. i have a fan on the radiator that works like a charm, new thermostat, flushed the whole system. In the end, I check the radiator cap and the rubber seal was cracked inside it. Once I replaced the cap, it ran nice and cool.
The test between the 195C thermostat and no thermostat was with the same cap. It resulted in running cooler while at speed. I bought a replacement cap anyway and put it on with no thermostat. That resulted in the same running as originally without a thermostat.
Sounds like you have the ground covered, but good to check anyway. Since you started the thread with this changing since you re-wired, that's why I went there...assuming that temps were good prior to the rewiring, or at least you assumed they were, what were you using to measure the temp prior to the new gauges and where were they reading?
Overall top temperature should have nothing to do with the thermostat temp, only how quick you may get there.
Timing, Radiator, fan, and/or fan clutch is where I'd be looking, but I think most have already covered those topics.
I too hear the gurgling after shut down, I think that is normal.
I did just switch to a new HD radiator (I have pics posted showing the size difference of the two). If yours came stock without, it should run fine with the smaller one. Can't hurt going to the larger one, but the process of changing (flushing and stuff) may be the actual fix. If it's your current radiator, getting it hot tanked and cleaned up from a radiator shop may do the trick, just as a new one would too....
I have a very hard time getting up to 200 now with everything replaced, running regular fan, no fan clutch.
I never was able to monitor coolant temp before the re-wire. One of the main reasons for the re-wire was to have a functional dash, lights (brake, turn, headlights). Prior to this, I just ran whatever temp it ran at, which to me seemed hot because the Jeep would diesel when I shut it down.
I do not have a HD radiator as far as I can tell. I also don't have a shroud, which I plan to get. The fan is clutch-less and is always spinning with the water pump. The idle heat I associate to too high and idle with no shroud, and can live with that until I get the idle tuned down.
My biggest concern is the difference in temps from a thermostat to no thermostat. I am not sure if the added restriction of the thermostat is an issue further compounding because my radiator is starting to clog up, the water pump is going bad, or I trapped air in the system somehow??
I think I should start with a system flush, either by myself or at a shop. Then work on a lower idle tune on the carb and either a fan shroud or electric fans.
Here's the thread I put out there that has pictures of the two different radiators, maybe it will help you determine which one you have.
A good flush of the radiator / cooling system would probably be a good start. Prior to swapping my radiator, I wanted to flush things out well too. I used some Prestone cooling system cleaner and ran that through, drained, then I rinsed and drained, then I dropped the radiator and replenished the coolant (I also swapped the water pump just to be fresh and all the hoses).
Bad thing about this is I have a bunch of coolant to get rid of now. That's the one advantage of having a shop do this as they may be able to do it quicker too (need to wait for things to cool down each time, takes time).
I was figuring I just wanted to start things from scratch, which is why I bought a new radiator. If you do take it to a shop to do, having them tank, maybe re-core the radiator (if needed), while they have it all apart would probably be a good idea. It would be a bummer to have a bunch of junk in the radiator, get this all refilled with coolant, then have that junk get back into the engine.