Cooling Questions

[cjkeeliii]

I have an '85 m1008 and its cooling system is making me scratch my head. Here are the symptoms:

Used to run between 182 and 195 then began running around 205 so I replaced the radiator. Then it ran around 110 to 130 from late Summer throgh now until I found a leaky freeze plug (never could keep the overflow tank full) so I installed a block heater a couple of weeks ago. Still ran 110 to 130 until a few days ago and now it runs 160 to 165 but the overflow tank is full.

I don't get it: is the water pump broken? If the water pump works is the water even circulating if it never gets hot enough to activate the thermostat? For those that haven't installed a mechanical temperature gauge, let me tell you that I've run two different radiators and the temp will always cool about 5-7 degrees when stopped, and the temp will rise about five degrees on the interstate because of the heat from the road. Right now it's cold here in Georgia, so when summer comes I don't know how this thing will act. The radiator is the standard four row, brass, and copper model from O'Reillys'. The block heater is a 1000 watt Zerostart. As cold as the weather is now-38- this thing should be running 110 to 120. Any ideas? Thanks.

 

[merace19]

have you checked to see if the thermostat is working. It may be stuck open. Thats the only thing I know of that will keep temps way down. that and a bad gauge. Which you can check by getting a cup of boiling water and dropping the sensor in.

 

[OL AG '89]

cj
I'll start from the beginning.

I think the correct temp for the 6.2 is 180 - 195. The TM has exact number.
Have you looked at that?
The engine "running" temp is not affected by outside temp. a proper operating cooling system will run at the correct temp whatever the outside temp is.
Unless under extreme load, then it may for awhile run a little warmer.

What mix of water / coolant are you running?
If you havent changed since you purchased and arent sure of condition, check with a hydrometer (?) I think that's what its called, can get one at oreilly, napa, advance....

Have you checked if the radiator is moving water?
start cold and let it warm up, once thermostat opens water will flow in radiator. If it flows immediately when you crank up cold, your thermostat is stuck open.
If it isnt functioning the temp will get much higher than 110 - 120.


Is the cap good?
pressure test at oreilly, napa, advance.... should hold 15 - 16 lbs.

there are so many things, the TM troubleshooting sections will always be your bwst bet!

 

[markg]

have you checked to see if the thermostat is working. It may be stuck open. Thats the only thing I know of that will keep temps way down. that and a bad gauge. Which you can check by getting a cup of boiling water and dropping the sensor in.

i agree, its the thermostat. do you have heat in the cab? put your hand on the heater hoses after running for a while . correct temp and you wont be able to hold them for more than 5 seconds.

radiator cap is usually good if it pulls coolant back in from overflow bottle when cooling.

 

[cjkeeliii]

What is the correct pound radiator cap? Looked on the net and the TM's, but don't get a clear answer. The one on the radiator is 13lbs.

 

[merace19]

13psi even if it held to that psi would not give the low Temp reading.. Check the 2 things I mentioned earlier..

 

[jacksmad1]

I agree you should check the other things listed in this thread first. I was having trouble getting heat in the cab, it was only lukewarm. After reading a lot of threads on here, it seemed I might have air in my coolant system, which it sounds like may be the same problem you have. Try to park your CUCV somewhere facing uphill that allows the radiator to be higher than the engine. I removed my radiator cap, started the engine, and let it get up to operating temperature. My crossover pipe has a hex head plug about an inch to the left of the thermostat housing. While the engine was running, I carefully loosened this plug with an allen wrench just enough to let any trapped air to escape without totally removing the plug. ( You may want to break this plug loose before you start the engine but not loosen the plug until the engine is running and at operating temp. Be careful of the fan blade which is just a few inches away ! ) Once coolant starts to leak out, all the air is out of the system. I tightened the allen plug back down and re-installed the radiator cap. After just a short drive down in the fields, I had real heat in the cab for the first time this winter. Outside temperature here today is about 35 degrees. Hope this helps.

 

[natemccabe]

I replaced my heater core his summer and hae had horrible heat since. I'll use the mentioned method to bleed out any air as I'm sure there is some in there!!

 

[just-speed]

I was looking for info on replacement Rad and saw this thread. I have to ask. It was siad standard rad was a 4 core? My 85 has a 5 core and I want to find one for my other Blazer. Anyone know where to find the 5 core? Is the 5 core in mine not standard?

 

[OL AG '89]

CJ
Any news?
I would read the TM carefully before breaking apart connections on a 25+ yr old vehicle. I have NEVER had to bleed and radiator as described in previous post. These vehicles were meant to worked on by the avg. joe. I know, used to be a 63Y/N. We would never work on a "running" vehicle, in close proximity to a spinning fan. I'm not saying the bleed method won't work, it just puts you in the line of fire unnecessarily.
Did you determine if radiator is flowing when you first crank up?
what about the condition of the fluid?

Good Luck