Followup-- 2000 JGC V-8 still overheating

OK Maybe your coolant system is so efficient that the neck area does not get super hot. Do you have a factory tow package on this Jeep? I will ASSuME that the coolant system is FULL and you can't add any more to the system. Since you can't touch the radiator maybe the coolant in the neck where you can touch is separated from the coolant inside of the radiator. Is the upper radiator hose hot or can you touch that?

Yes usually if your engine is working harder it will get hotter. If the radiator or cooling system is not up to the task then the coolant temperature will rise. ALSO if the engine runs lean or has other issues such as a partially clogged cat then the engine could run hotter too. Has it been tuned or serviced recently? New filters, air and fuel, spark plugs, etc.?

Did you feel the neck of the radiator right after a good highway trip at 75 mph? BUT PLEASE DON'T REMOVE THE CAP!!

Running out of ideas without seeing this Jeep. ;-) good luck!

You had no coolant flow?

He has no coolant flow with the rad cap off....

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >

That is just it!!!!

He HAS done this! He has 'no' coolant flow with the rad cap off the rad!

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06 (More Off Road album links at bottom of the view page)

Could you possibly have the wrong water pump in there?

They make 2 pumps that fit in the 4.0, a normal one for V belt engines and a 'reverse' rotation one for serpentine belt engines. I don't know if the V8 is the same....

Having no flow and cool coolant with the rad cap off but it 'doesn't boil over is very weird....

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >

Without chasing all wthe way back through thread has he checked for a hose collapsed internally blocking flow?

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

Mike, it is the original water pump. SnoMan, yes, the fan does run at idle, with temp at 205.

Yes, I do have tow package, and the coolant is full. It is up to the very top of the neck when I take the rad cap off. There is NO circulation of the coolant, and it is warm, but not really HOT, even when the gauge is at

205.

I think my next step is to take it to a rad shop and allow them to take the rad out and test it.

Yes, I could have another "bad" (new) thermostat, but I don't know how many times I should try that. (I am not a mechanic, so I can't do that myself, so I have to leave it for a day when I have work done).

Coming from the viewpoint only of a lay person (non-mechanic) I just doubt it is a water pump or fan clutch problem. Could be another bad thermostat, OR a flow problem in the rad system.

It just seems to me that if the car does fine at idle (can run all day at a redlight and not heat up), but heats some at 75mph and heats a LOT on long incline, no enough coolant is circulating around the engine. Again, this is just from a "lay" person.

I do appreciate all of the comments though, thank you all!!

--James--

I just made a call to a buddy in the OEM automotive thermostat business who knows the T' Stat technical part pretty well, maybe he'll join in.

Talking to him ... he recalls that the 4,7 has an Inlet Side T' Stat - meaning that it controls the flow of coolant back into the engine from the radiator. This contrasts with typical / conventional T' Stats which control the flow leaving the engine.

Chrysler had some issues with the Front Cover in '99 and 2000 when the

4.7 was first introduced. The front cover mixes coolant circulating from the block with coolant coming back from the radiator. This mixed temperature is what the T' Stat sees and increases or decreases the amount coming from the Radiator (there are lots of good reasons why an inlet side T' Stat is a good idea). The problem that DCX had was that this mixing volume in the front cover didn't quite work right and some owners had problems from day one ... I believe the fix involved replacing the front cover which isn't a simple job on this integrated accessory drive motor.

With this inlet side T' Stat control the diagnostic logic isn't the same as on conventional T' Stat engines - such as when a T' Stat is installed backwards.

Regarding the coolant flow problem open cap at warm idle - if the coolant is warm there is some flow taking place - simple physics. That you cannot feel or see this flow means it is very low - and, since this is a cross-flow radiator you don't see flow across an upper radiator header like you would in a down-flow radiator. The radiator inlet connection is down part way on the inlet tank and the flow goes through the radiator core, most not seeing the light of day when looking in the filler neck.

I just called another buddy about the fan system on this car - the difference between trailer tow and non-trailer two configuration... he worked on the fan system when he worked for Delco in the time frame. He says that the JGC needs to have the engine driven fan operating at highway speeds, that the ram air alone wasn't sufficient to keep the coolant temperature controlled by the T' Stat.

The conventional (non trailer tow) system has an electric fan on the engine side of the radiator inside the shroud (with enough power to make the condenser work in air conditioning) and a engine driven fan with a Delco fan clutch. This fan clutch was engineered for very low drag - meaning that unless the bi-metal kicked it in the fan turned at a low speed - you can stop the fan at idle with a pencil. Even kicked in the fan clutch wasn't a real high torque clutch.

The trailer tow system was similar - an electric fan behind the radiator and an engine driven Delco 1525 fan clutch with a higher torque rating.

Your system is acting 'cooling limited' in that the coolant temperature is a function of engine load. There are two possible causes for this in the first breakdown.

- low coolant flow (as from an internally restricted radiator or a collapsed coolant return hose

- low airflow with two possible causes - blocked air path (bugs, mud, bent fins, airside corrosion - inoperative fan

The blocked air path can be determined by looking at it - is the condenser covered with dead bugs, do you have a bug screen, is it or the radiator plugged up with dried mud (clay gets like concrete) or is there a lot of white 'fuzz' corrosion on the louvers in the fins. If it is bugs or mud you can clean it with a garden hose, don't use a pressure washer or you'll fold the fins over and need to replace the heat exchanger.

The inoperative fan can be checked this way - dig out the RTV holding the leg of the bi-metal coil in position and lift it over the boss on the clutch cover and rotate it counter-clockwise, let it rest against the boss from the other side. This will leave the fan always engaged. After driving the car to fully warm shut off the engine and see if there is significant drag when you try to rotate the fan by hand. If it spins pretty easily then the clutch is out of fluid and needs to be replaced. If there is drag and the cooling problem goes away you need to replace the clutch. If there is drag and the cooling problem hasn't gone away then it is either problem with bugs / mud or internal restriction on the coolant side of the radiator.

I would try the fan clutch bi-metal coil first - it doesn't cost anything, its easy and it doesn't risk screwing anything up ...

reboot

James proclaimed:

Cheap cooking thermometer will get the real temperature, but all symptoms so far say either your thermostat is not opening or your water pump is not working overly well or there is a blockage.

If you go to that expense, might as well replace it with an aftermarket, but that sure seems like way too many dollars spent rather than troubleshooting.

A *good* cooling shop would have already checked your water pump for flow and your thermostat for opening and your system for blockages that impede flow.

Or a very small head gasket problem that lets exhaust into the fluid but only at higher engine speeds [not that probable from your symptoms so far].

As a diagnostic, remove the thermostat. Yes, your engine may warm up slowly and fail emissions during warm up, but at least you've removed the easy part of determining if the thermostat is bad as installed.

If you don't see flow with the thermostat removed, your water pump is bad or you have a blockage.

You can test the thermostat while it is out by putting it in water and slowly heating the water to see if the thermostat opens. Again a cheap cooking thermometer works.

It really isn't that difficult to remove possibilities, but it works better if it is done scientifically rather than philosophically--which isn't doing that good so far.

If you let it idle and it doesn't overheat, you should still have coolant going thru the radiator. Your fan should also be cycling.

If your coolant isn't flowing [which is admittedly incompatible with many of the symptoms proposed] the engine heats up...which may not be obvious if the coolant cannot hit the temperature sensot. A second means of measuring coolant temp is a good idea... the radiator coolant should heat up but measure it, don't assume.

Oddball ignition can heat an engine at higher load as can a head gasket leak, but both of those tend to have other symptoms and I'd hope your PCU would throw a code on ignition retard.

Heating at 75 and on inclines usually mean someone has replace a major part of the cooling system without quite knowing what they are doing.

reboot, thank you for the very nice review !!

You and one other chap mentioned a possible lower hose collapse. That suggestion had been made before, and I will add it to my list as I sort through this.

Thanks again to all !!

--james--

They usually do at a idle warm. What happen when the RPM goes up for

1500 RPM or more warm. THe Jeep I had heating problems with 15 years arond "worked" at a idle too but not at higher RPM's when needed

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

James,

My money is on a bad water pump, thermostat, or clogged radiator. No coolant flow in the radiator at idle when warm could only be one of the three. Pull the upper and lower rad hoses and flush it with a garden hose, or just pull the radiator and have it cleaned and re-cored. While it's off replace the water pump, and thermostat (yes, do it again), flush the entire system and watch your cooling troubles go away.

Hope this helps,

Carl

Wouldn't a bad water pump that causes a "NO-FLOW" situation also cause no heat in the cabin? James are you freezing inside of the Jeep or do you have fantastic heat?

The answer should help you guess if it is the water pump causing your problem(s) or the thermostat and/or radiator. Whoever installed the thermostat should check your system out for you! ;-)

If you are getting good heat inside the Jeep, I guess I would start with another thermostat also. Make sure it is a good brand!!

I worked on a vehicle that had a defective oil cooler. This allowed oil into the coolant system and everything turned into a very thick paste-like crud. It clogged up the radiator hoses, heater core and the radiator causing the engine to overheat. I don't think that this is your problem.

8^o good luck! later, dave AKA vwdoc1

Good point. Do you have heat? If you do, it's the radiator.

Carl

Oops, I missed that. Probably came in from work and fired up the 'puter without eating supper first. Just like I did tonight, and I'm about to starve.

Dan

Someone mentioned that the thermostat is supposed to go in 'backwards' on this engines setup??? If the installer isn't aware of this.....

Inside heat can be deceiving. Most engines have a thermostat bypass so hot coolant can get to the heater core before the thermostat opens.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail > Good point. Do you have heat? If you do, it's the radiator.

James wrote: I let the engine run for 45 minutes. The gauge went to 205 and stayed there. At no time did I see a water flow, even after 45 minutes of running at idle. I put my finger in the water and it was **warm** but not at all hot. Just warm. It never got hot.

Mike Roman responded: I let the engine run for 45 minutes. The gauge went to 205 and stayed there. At no time did I see a water flow, even after 45 minutes of running at idle. I put my finger in the water and it was **warm** but not at all hot. Just warm. It never got hot.

I still think it would be good to verify the temp guage is really showing the correct temp. Where is the temp sensor that the guage could read >200 and the coolant not burn a finger?

But then, what do I know? I have not worked on my on vehicles for years...

Regards, doug

I am not aware of any that do not bypass Tstat for heater. It would be kinda silly not to.

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

No flow is only caused by four things. Clogged radiator, clogged block, bad t-stat, bad water pump. Tell us if the heat is working. If it works well, it's the radiator.

Carl

You forgot collapsed or clogged hose.

Earle