Followup-- 2000 JGC V-8 still overheating

Did you touch the radiator at different spots/corners to see if it was getting hot at all? Upper radiator hose getting hot?

Might be a partially clogged radiator and the area where you touched with your finger is part of the clogged area where the coolant possibly stays cooler. I would assume that if the water pump was not functioning then that engine should overheat just idling.

Just a theory. later, dave AKA vwdoc1

The place where I was touching was in the water itself. I took the pressure cap off for the test. The water is just under the cap.

--James--

I would be thinking that the thermostat that is supposed to open at 195 has serious issues.

You should have burned your finger in 205 coolant. Water boils just slightly hotter than that....

Mike

Yes, Mike, I agree with your comments. My mechanic put in a new thermostat just several months ago. I wonder if it was installed backwards. Could that be ?

--James--

Or just plain a bad one.... That happens. I think yours must be opening 'some' or you would get a boil over.

Mike

I fully disagree here. He can keep chasing monkeys but I am pretty sure it is one of three problems. THe first that the core is blocked externally with dirt and bugs limiting air flow through it. The second is the clutch fan is bad because contray to popular belief ram air will not always cool engine especaily when a big V8 is packed in a small compartment. Some seem to think that they never good bad but the thermostatic coil on them ages and when it does it retards the operation of the fan. (I have posted instruction on how to adjust the clutch fan in my forum) When it is 220 or so the fan should be a humping. The thrid is the core is blocked internally which can happen if proper coolant quality is not maintained. I would check it in that order or you can just keep chasing the monkey around and never catch it.

----------------- TheSnoMan.com

SnoMan, I had the fan clutch replaced about four months ago. Yes, I know it could be defective, but talk about chasing monkeys, I am not quite ready to put another clutch in. You posted a very good article on adjusting the fan, but my mechanic indicates that for the labor involved, he would only go with another new fan. I am not ready for it, as I see that as doubtful.

When you say the "core" could be blocked, exactly what part do you mean ? Are you speaking of the radioator itself ? I am thinking more and more that it is the radiator. Perhaps you mean the radiator core, huh?

Can a flow test be done without removing the radiator?

--James--

First when the engine overheats is the clutch fan engaging? Next on the blocked core it could be that the external part where air flows through is blocked with dirt or bugs or the fins are badly smashed blocking airflow. Internally, you might find a shop to flow test it in car but not too likely. Feel core of raditor (if possible) and see if it is evenly heating up. I still stand by my 3 suggestions. because the symptoms match it.

----------------- TheSnoMan.com

If something was indeed blocked, he would get boiling fluid pouring out the open radiator cap in the test. He has cool non moving fluid only with the inside gauge reading above the temp an open thermostat would be working at.

He could have no real problems with the rad and a wonky sender for the gauge.

Mike

SnoMan wrote:

Could you be sticking his finger in the wrong area? Had to ask!! You keep saying 'water' and not 'coolant'. This is the radiator cap right?

I have known people that add coolant to the engine through the oil cap or into the washer bottle.

I had to ask since it is hard to believe that your pressure cap allowed you to take it off safely and the coolant was only warm AFTER you have been running the engine for awhile getting it up to normal operating temperature. ODD!!!

You still did not answer my question about the temperature of the radiator measured at different spots like all four corners!!! You might have an extended neck on the radiator which might cause that coolant there to not move around much. Touch the outside of the radiator in the corners AFTER the engine is at normal operating temperature.

This sounds a little unbelievable to me!!

JMHO

But Mike, how would the faulty sender know when I am doing 75mph rather than 65 mph ???

It is normal temp at 65, and 15-25 degrees hotter at 75. I doubt a faulty sensor would act that way.....

Yes, I took the cap off after the car sat overnight. I ran it for a total of 45 minutes. Yes, I put my finger in the COOLANT, and yes it was warm but no where near hot. The gauge temp was about 205, even after 45 mins no hotter , and no detectable flow. I assume the coolant in the nec (where the cap goes) would be gurggling or bubbling, etc if there was flow. The coolant was even, and not disturbed.

I have not checked the spots on the four corners, as you cannot get to it.

--james--

I have no way to know this. I can't look at it or hear it at 75 mph.

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First when the engine overheats is the clutch fan engaging?

Thanks Bill. The thermostat was bought from NAPA, and specified for this vehicle. 4.7 engine.

As I said in the other group, it could be defective, but it just sounds to me like my experience with a stock radiator that was a little too small for the engine.

Dan

Dan, if the "stock" radiator in this Jeep is just a bit too small for this engine, why do you think it never overheated in the first 125,000 miles ?????

Surely, you are not suggesting that the radiator shrunk a bit during this time................................. are you ???

Respectfully, I don't quite see your logic..........

--james--

IF the clutch fan started to engage at 65 or 75, you would know it unless you have a very loud stereo or exhaust system. Many years ago I had a over heating problem with a old Jeep truck in the winter plowing snow but only when transporting, not when plowing. . It turned out the between the cold air temps preventing thermostatci clutch fan from engaging (it is based on air temp coming thru core not coolant temp) and disrupted flow of air from plow at speed the truck would start to slow cook and get pretty hot. The cure was a more agressive clutch fan setting. Not say this is for sure your problem but when you stuff a big engine in a little compartment you can have cooling issues sometimes because ram air does not always cut it. If you get guage hot and stop and idle does clutch fan engage then?

----------------- TheSnoMan.com