overheating need help

[blown XJ]

ok so i have a 89 jeep xj with a 4.0 motor. i cant drive it at all with out it out it overheating.. its got a new water pump, a new tstat. the raditor is about 3 or so years old. im running out of ideas on what it could be. any help would be awsome..

i heard some where you can put a comanche raditor into a xj and get a really raditor cap instead of the crappy coolant bottle on the firewall. is this true? if so what years of comanche's are the right ones to get a raditor for?

thanks for any and all helps

 

[SteelHeadz]

With the new water pump and new thermostat, and still overheating, did you check your cooling fans for proper operation?. A 3yr. old radiator is not a likely cause for the overheating concern unless it's leaking or it's plugged up. Have you done a pressure test on your cooling system?. Overheating is usually caused by a minute leak or lack of circulation. Leaks can be internal or external. Internal leaks are best diagnosed by using a combustion chamber coolant leak chemical tester. This chemical is blue in color and will turn yellow when it mixes with the combustion gasses. If this is the case, the possibilities would be a crack on the head, bad head gasket or a crack on the block. In some occasions, a head gasket leak will cause the coolant to mix in with the engine oil which would make it look like a mocha cappuchino without the extra shot of espresso. Check the cooling fans first. If that's ok, pressure test the system. The last resort is the internal leak test.

 

[Sly8795]

I went through the exact same issues and steps as you. Your real problem is probably the 10 dollar temperature switch that the gauge reads on thats located at the back of the block on top.

Once I replaced this I realized I actually never overheated one time because I was testing my rig one time in 4x4 low and it actually start to run hot and the a/c fan kicked in which had never happened before.

Id replace that switch burp the system and then see what happens.

 

[blown XJ]

what is this temp switch? i know im overheating by the steam coming out of the hood. my jeep has no temp gauge on it. i have one but i have been out of town for work so i havent had time to put it in. i drove it about 5 weeks ago no prodlem. it sat till last nite and overheated. im at a loss for why it did so.

 

[SteelHeadz]

what is this temp switch? i know im overheating by the steam coming out of the hood. my jeep has no temp gauge on it. i have one but i have been out of town for work so i havent had time to put it in. i drove it about 5 weeks ago no prodlem. it sat till last nite and overheated. im at a loss for why it did so.

A stuck thermostat may cause the overheating. You didn't mention that it has sat for awhile. It could be as simple as that. The 4.0 liter engine has a coolant temp. sensor located at the top of the thermostat housing. This is an input to the PCM for the electric rad fan module and the PCM supplies the output for the cluster.

 

[blown XJ]

on the therostate housings? for the sensor.. i dont have any senors the hook into the tstat housing. i hard wired the electric fan into a switch and put an aftermarket flex-a-lite fan in place on the stock electric fan

 

[SteelHeadz]

When the engine temp. is at around 185 to 190 degrees and you flip your fan on, when the overheating occurs after that, are the upper and lower radiator hoses about the same temperature?. If not, there is a circulation issue. If the overheating occurs while driving and causes a boilout condition, Check the radiator cap for proper operation. If that's good, go to napa and and invest on a block tester. its around $45.00 and worth every peny to make sure your not going to blow up your engine due to an overheat problem.

 

[blown XJ]

yes the hoses are about the same temp. i have got in the habit of turning the fan on when i start the jeep and just leave it on the time, as i dont have a temp gauge. i also do not have a raditor cap. it has the crappy coolent bottle with a plastic raditor cap. i have decided that im going to take it into a shop and have then put a raditor with a regular style cap and overflow on it. hopeful a 3 core aluminum one. i have a 2 core now. i have ran out of ideas. and im tired of it getting hot every time i go wheeling.

 

[MoparMatt77]

If your Jeep has AC the electric fan stays on when AC is on. You may either have a small leak, faulty coolant overflow bottle, cap, or an air bubble. It's the design flaw with 87-90 Jeep 4.0L closed loop cooling system. If everthing is working perfectly it'll overheat too easy. I have done the open loop cooling conversion on 3 jeep 4.0L's. No overheating issues after the conversion. I also kept the original radiator too.
Here's more info on conversion:
Open System Cooling Conversion

I used Summit.com for a better price. Moroso p# 63745 msrp $26.99 ea

http://store.summitracing.com/partdetail.asp?autofilter=1&part=MOR%2D63745&N=700+115&autoview=sku

Summit catch cans p# SUM-G1372 $16.95 ea

http://store.summitracing.com/partdetail.asp?autofilter=1&part=SUM%2DG1372&N=700+4294924500+115&autoview=sku


Napa online for 91-01 Jeep 4.0L Heater control valve #BK 6601272 $18.99. NAPAONLINE

 

[Sly8795]

what is this temp switch? i know im overheating by the steam coming out of the hood. my jeep has no temp gauge on it. i have one but i have been out of town for work so i havent had time to put it in. i drove it about 5 weeks ago no prodlem. it sat till last nite and overheated. im at a loss for why it did so.

ah didn't realize that it was actually blowin smoke. I have a temp gauge in mine its a 90. the temp switch is located on the back of the head thats what i used to bleed my system as well.

 

[MoparMatt77]

what is this temp switch? i know im overheating by the steam coming out of the hood. my jeep has no temp gauge on it. i have one but i have been out of town for work so i havent had time to put it in. i drove it about 5 weeks ago no prodlem. it sat till last nite and overheated. im at a loss for why it did so.

ah didn't realize that it was actually blowin smoke. I have a temp gauge in mine its a 90. the temp switch is located on the back of the head thats what i used to bleed my system as well.

Correct if wrong but 87-90 4.0L has tempeture thermal switch in bottom of radiator next to Lower hose or in a factory tee in lower hose itself. If it has gauge it has temp sending unit in back corner of cylinder head. Switch turns fan on and sender is for gauge. 91-01 4.0L has combintation sending unit and switch in Tstat housing. 91-01 switch is signaled through ECM. IDK 'bout 87-90 but 91-01 fan also switchs on when you turn ac on.