Help, Im stumped...

I have a 1990 Wagoneer Limited with a cooling problem. Seems to run cool around town, but at highway speeds, it runs hotter than I think it should. Around 210 around town, but on the highway around 220-235. Ive replaced everything I can think of, new t-stat, new water pump, new fan clutch, hoses, etc. Im at a loss. Its a 1990 Wagoneer Limited, mostly stock, 3 inch lift, 31's, everything else is stock, gearing, etc. Any advice offered would be great. Thanks...

Do you have a transmission cooler? When under constant power on the freeway or towing your tranny can warm up quite a bit and effect engine temps. Just a thought..

No, I dont have an aux tranny cooler. Thats on the list to buy, but I may not if I cant get this running hot problem sorted out.

A new radiator???

Just some thoughts.

You've modded your ride ...jacked it up ...put larger tires on it but have stock gears. The oversize tires effectively lower your final drive ratio ....and raising your ride increases the already dismal drag coefficient of the little "brick on wheels". Got some roof top stuff too (light bar, rack, etc)??? ...more drag. Your engine is more than likely working much harder to punch through the atmosphere at highway speeds and it's showing on the temp gauge. For most vehicles, the biggest resistance the engine faces above about 40mph is wind resistance.

I would upgrade the stock cooling system to compensate for the other mods you've done. New radiator ...three core ....brass and copper. Water pump ....high flow ....Summit Racing has FlowKooler pumps for the 4.0L.
Slip in a balanced flow 180deg T-stat ...to compliment the better pump. Get a tranny cooler and mount it on brackets *away* from the radiator (rather than mounting it *on* the radiator). Out side of these suggestions I would consider some hood vents to allow better flow through the engine bay. There's a website... http://go.jeep-xj.info/HowtoBonnet.htm ...and this guy did some interesting tests to see about getting better airflow through the engine compartment (which equates to better airflow through the radiator ....and ultimately a cooler motor).

Like I said, just some thoughts. Hope this gives you some ideas.

mike
00XJ

when you do replace the radiator, switch over to an open system, and buy a good replacement, i run a genesis auto all aluminum, it runs about $150. i dont run hood vents, and have zero cooling issues. couldnt be happier.

boonie said:

I have a 1990 Wagoneer Limited with a cooling problem. Seems to run cool around town, but at highway speeds, it runs hotter than I think it should. Around 210 around town, but on the highway around 220-235. Ive replaced everything I can think of, new t-stat, new water pump, new fan clutch, hoses, etc. Im at a loss. Its a 1990 Wagoneer Limited, mostly stock, 3 inch lift, 31's, everything else is stock, gearing, etc. Any advice offered would be great. Thanks...

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Common reason for higher temps at highway speeds is because the radiator is gummed up ....

Make sure theres nothing blocking the fins like leaves, bugs or mud .... and then try a flush for starters ... and see if theres an improvement.

Replace it if its not doing its job ... Its the main provider of cooling on the vehicle ... followed by an effective fan ... all the other bits just help move the liquid around ... but they still need to be in good nick too.

A good quality, well designed 2core in copper/brass should be more than adequate for most circumstances.

All the points above by jocko463 are relevant ... but you need to ensure the basics are right ... before doing any modding to suit your vehicle setup.

With a decent radiator and fan ...
You shouldnt need a hi-flow pump ... especially as too fast, flow rates can create additional problems.
You also shouldn't, need a thermostat any lower than 190'f.

As for vents commonly shown fitted on forums .... They are just to allow the buildup of underbonnet heat at low speeds - to escape utilising the basic physics principal of "heat rises" ....

You need to do something different to actually improve engine bay airflow .... especially at highway speeds.

I already put a new radiator in it, all aluminum, and converted the system to an open one. May try the high flow water pump next.

Coolant mix 50/50 ethylene glycol/distilled water? Change it to 30 ethylene glycol and 70 distilled water.

Check your radiator cap. If your loosing pressure from your cap it will cause your water to boil and jack your temps up. I have seen a couple Jeeps have cooling issues and everything was replaced except the dumbest smallest thing; the radiator cap. My wrangler had a very similar isssue as your rig and I repalced everything with no success. Finally spent $12 at napa for a new cap and my overheating issues went away. Just a thought.

bhicks said:

Check your radiator cap. If your loosing pressure from your cap it will cause your water to boil and jack your temps up. I have seen a couple Jeeps have cooling issues and everything was replaced except the dumbest smallest thing; the radiator cap. My wrangler had a very similar isssue as your rig and I repalced everything with no success. Finally spent $12 at napa for a new cap and my overheating issues went away. Just a thought.

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And a good thought it is.. I would check/replace the cap before continuing further with any mods at this point.

Ok, heres an update. To date, I have replaced the radiator cap, thermostat (again), and temp sending unit. Still overheating. IR temp gun shows 195 at thermostat housing, head never above 190, yet gauge still says 215 and above. Im at a loss, not sure where to proceed from here. No radiator blockage at all. 180 degree thermostat, and still hot. System converted to open style. If I cant get this sorted out, I may end up selling this and starting over. Any suggestions...?

Infra-red says 195-215. Gage is no good. You replaced the sending unit. That does not guarantee that the gage is right. Just pretend your gage is really saying 195 when it says 215. If it goes to 235, start to worry. It isn't overheating until it's boiling. With the radiator cap pressure, it won't even boil until at least 230.

Simple, test your gauge:

100 degrees F = 1365.0 ohms
200 degrees F = 93.5 ohms
260 degrees F = 55.1 ohms

Stop at Radio Shack, buy some resistors, check the gauge's accuracy.

Did you test your coolant mix yet? Is it at 30/70?

ALSO--when you start a thread, provide ALL of the pertinent information up front, if possible, like the new radiator/open system conversion. Makes things go smoother, and it doesn't waste other peoples' time.

I have heard of aftermarket temp sending units causing the gauges to read high. Follow Joe's suggestion on testing the gauge/sender.

Ok, this may be a dumb question, but how do I go about testing the gauge? Resistance across the connections?

no, you need to ground the gauge lead using a resistor of a known value and see what the gauge reads. Joe provided you with the resistor values.

If you've verified that the motor is not overheating with an IR gauge I would just make a note of what normal operating temp is on the gauge and run it. The temp gauge is not a precise measuring device, it's just there to let you know when you're getting into trouble. If it really bothers you that much, replace the cluster, or make a new overlay with numbers that correspond to your gauge.

You may also try a new thermostat housing from an HO, and relocating the temp sensor to the thermostat. You can leave the old sender in the head or plug it with a brass plug. It's possible that you've got a hot spot on the back of the head. Indicating some sort of flow problem in the block caused by blockage.