258 running hot,220-240F???!?!?!

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.

Any help would be greatly appreciated.

Thanks,
Scott

Sorry for the long post.

 

I want to add that when I shut my Jeep off, I can hear what sounds like a water trickling sound.

Scott

 

When was the last time the water pump was changed?

No thermostat...no restriction...everything is okay.
With thermostat...little bit of a restriction....runs hot.

It could be the fluid isn't circulating enough...bad water pump? Or maybe the belt is slipping...or the fan clutch isn't catching?

Of course, having a shroud would probably help a lot also.

 

Yeah, highway temp should be ok, shroud, fan or not. If the air temp is not blistering hot.

Using the Autometer sender or the Jeep sender?

You can get an infrared thermometer from Harbor Freight for about $20 I recall. Might be worthwhile to point it at the radiator and compare that to the temp reading.

How's the radiator? It seems that the most common cure for a problem like this is a new radiator. Do you know the Jeep's history? How long hae you owned it?

 

I am using the sender that came with the Autometer guage. As for the history of the Jeep, I have owned it for about 2.5yrs. The radiator was supposedly replaced not long before I bought the Jeep, and it does in fact look to be in good shape. The fan is mechanical, no clutch, so it isn't that. The belts don't appear to be slipping nor is it making any noise.

I am guessing the next step is water pump or flush the system?

Scott

 

So, let's go back, did you have a working temp guage before last Easter, do you know what temp it ran before?

 

Unfortunately, none of the guages worked on the dash except for the Speedometer every now and then, that was the main reason for the re-wire (among light issues). So I don't know how long this has been going on for, but once I had a working temp guage, it just seemed a bit high. Now that I can run cooler without a thermostat, I feel something is wrong and the Jeep should be running cooler. I just am not sure what needs fixed/changed, be it the water pump, radiator, complete system flush???

Thanks
Scott

 

A friend has a Jeep of similar era that ran hot.
He needed to get the timing right, a shroud and strangly, reverse the fan.
The fan had some cupped blades and whoever replaced it before had it in it's less efficient orientation.
I don't think it was the original fan.

 

Did your friend have issue at speed?? I understand my idle will run hot because the idle speed is set high and I do not have a fan shroud. My concern comes from the higher temps at speed when the airflow is provided by the vehicle speed and not the fan.

I am looking for help on what to work on since I run colder without a thermostat. Does that imply a new waterpump, flush radiator???/

Scott

 

Did 74's have a shroud from the factory?

And I agree with timgr, check the radiator temp with another gauge if possible for comparison.

 

Did you put teflon tape on the threads of the sending unit? If so remove the tape so the sender is metal to metal contact, any added resistance will throw the reading off. Just a thought.

 

I agree tape might make the reading off, but it would be off on both tests (thermostat and no thermostat). Although I feel teflon tape on the threads wouldn't be a big issue because the threads are not what is measuring the temperature. It is the end of the sensor that is in the coolant, and the resistance change due to that growth of the metal that should be giving the resistance change, and ultimately the temperature change. My largest issue right now is how to get the Jeep to run at least as cool with a thermostat as it does without one.

Does anyone know of a test to determine if I need a new water pump or to flush the system???

Scott

 

Yes, his still runs warmer at highway speeds.

 

I think you might be interested in this, considering the brand of gauge you're using.

http://www.madelectrical.com/workshop/water-temp-gauge.shtml

As far as a water pump test, I ain't a water pump expert, but if it still has fan blades on the back side and isn't leaking, there ain't a whole hell of allot else that can go wrong with it.

Did things seem to get hot before you added the gauge? Smells, gurgling sounds?

What's your anti-freeze mix ratio?