Thermostat replaced - STILL HOT

KeighJeigh · **Posted:** Sat Aug 23, 2008 7:06 pm

It's been over a week now. Lots of money, lots and lots of time. I replaced the thermostat (twice, because the first time the gasket leaked). New sending unit. Back-flushed the entire system as thoroughly as possible and checked for flow through every hose I had access to. I put in new antifreeze. I rinsed the cooling fins thoroughly and checked for debris. It has a new EGR valve, recent oil change and new air filter.

Exactly the same symptoms as before: AC on, warm day. Everything looks normal until I get 1/2 way up my mile long driveway and the gauge begins to climb - just a bit at first but then more and more until I reach the top and, depending upon ambient temperature, it shows from 3/4 to pegged. And yes, the engine is actually hot and there is no gauge cluster recall for my VIN#. The electric fan is on. The engine has never eaten fluid, there is no steam in the tailpipe and no bubbles in the coolant. The engine runs very well (better now that I have replaced the EGR) and gets normal fuel mileage with plenty of power on the passes. Thus far I have not seen it overheat at highway speeds - just when under stress at lower speeds. I put in a nifty purge valve at the top of the thermostat housing so I can purge any air in the system.

The only thing I can think of to replace is the fluid clutch fan. When I check it by trying to spin it fast, it only spins 3/4 of a turn or so and stops so I assume it is probably OK.

I'm now back to the same place I was last week with nothing changed but less money in my bank account.

What am I missing?

- Chris

PS- I have a full set of pictures and was going to do a write-up of the thermostat replacement and modification for the bleeder screw....but not until I get this d@mn thing fixed.[/b]

moto-scoot · **Posted:** Sat Aug 23, 2008 7:26 pm

you have checked for coolant flow
ive seen some water pumps with the vanes slippng or off altogether
none with this engine though
just a thought

KeighJeigh · **Posted:** Sat Aug 23, 2008 7:39 pm

moto-scoot wrote:

you have checked for coolant flow
ive seen some water pumps with the vanes slippng or off altogether
none with this engine though
just a thought

I considered the water pump and checked for anything that would indicate it wasn't working properly. No debris, no loose bearings, no strange sounds, no leaks. The only water pump failures I've ever seen involved those issues. The car only has 37K on it.
The water pump is even harder to get to than the thermostat. Unless I can find a really easy way to check the thing, I cringe at the thought of another week of working on it, probably a couple hundred more dollars, no use of the car and in the end, a nice new water pump that doesn't solve the problem.

Ranger1 · **Joined:** Mon Oct 17, 2005 7:40 pm **Posts:** 1137

Does it overheat with the MAF plug pulled?

I didn't notice in your posts if you had the cooling system pressure tested. Depending on what it costs, it might be less expensive to buy a new coolant cap first. I think someone already suggested buying a coolant cap with a pressure gauge in it to see if it's fully pressurized when hot. If it won't hold pressure, it's not going to cool correctly. If you've already done this test, my apologies. I skimmed the thread.

Definitely try disconnecting the MAF(ORM mod) and testing the same drive again.

Look at the coolant overflow tank while the engine is idling - do you see coolant flowing from the black hose on the right side of the tank? You should be able to see the fluid pumping into the inside of the tank for about an inch in a steady stream at idle.

KeighJeigh · **Posted:** Sat Aug 23, 2008 8:02 pm

Ranger1 wrote:

Does it overheat with the MAF plug pulled?

I didn't notice in your posts if you had the cooling system pressure tested. Depending on what it costs, it might be less expensive to buy a new coolant cap first. I think someone already suggested buying a coolant cap with a pressure gauge in it to see if it's fully pressurized when hot. If it won't hold pressure, it's not going to cool correctly. If you've already done this test, my apologies. I skimmed the thread.

Definitely try disconnecting the MAF(ORM mod) and testing the same drive again.

Look at the coolant overflow tank while the engine is idling - do you see coolant flowing from the black hose on the right side of the tank? You should be able to see the fluid pumping into the inside of the tank for about an inch in a steady stream at idle.

Good suggestions!

I just swapped my wife's 06 cap for mine and will test. I'll go into town right now & see if I can get a pressure gauge before the parts store closes.
If that doesn't do it, I will then try unplugging the MAF (the one on the air filter housing....right?) How would the mass air flow sensor affect overheating?

Unfortunately, it is now cooling off so my tests will become more difficult to recreate.

Ranger1 · **Joined:** Mon Oct 17, 2005 7:40 pm **Posts:** 1137

Yes. The MAF sensor when pulled will disable the EGR almost completely. The idea is to see how much, if any, reserve cooling you have left without the egr induced heat load.

MrMopar64 · **Posted:** Sat Aug 23, 2008 8:54 pm

For sure it sounds like the viscous fan clutch is bad. I just got back from a hot trip out west, had the same problem on a car - swapped the fan clutch, problem went away. Do you have a fellow CRD driver in the area that maybe you could do this with to see if the problem follow the part or not?

KeighJeigh · **Posted:** Sat Aug 23, 2008 9:14 pm

Ranger1 wrote:

Yes. The MAF sensor when pulled will disable the EGR almost completely. The idea is to see how much, if any, reserve cooling you have left without the egr induced heat load.

I made 2 runs with the cap swapped from my wife's 06 CRD - no difference.

I then made 4 runs unplugging and then plugging in the MAF - some difference but not much. If the gauge was 7/8 before, it was perhaps 3/4 after. It's a very bizarre problem
because it requires certain specific conditions:

* It only begins to rise after I'm 3/4 of the way up the driveway. It has to be fairly warm (over 70 deg), it helps if the AC is on.

It is a steep, gravel driveway - mostly under tree canopy - and the speed is 10-15 mpg max.

The driveway gains 600 feet in this last short stretch where I've been testing it and there are a series of small flat spots - perhaps 200 ft long. Flat spot 1 shows a tiny rise in temp. Flat spot 2 shows another notch. Flat spot 3 is where it begins to rise more dramatically ...and then as I pull into the parking lot level with the house, it starts to really rise. Just as I park, it peaks out and then slowly begins to go back down as I let it idle.

Ranger1 · **Joined:** Mon Oct 17, 2005 7:40 pm **Posts:** 1137

Ok,

You've eliminated the thermostat, the coolant cap and egr heat load. When your temp gauge shows 3/4 the mechanical fan should be running wide open. Once when my thermostat stuck as I was pulling in my driveway, I popped the hood and the mechanical fan was turning but not very fast, not a lot of air flow. As soon as the t'stat opened, with the gauge at near 3/4 scale that mechanical fan took off with a roar I've not heard since. The electric fan also hit the high speed setting. The fans were very loud, a literal roaring sound. It was really pushing some air at idle.

If yours isn't moving a lot of air when at 3/4 temp, I'd follow MrMopar's suggestion and switch viscous couplers with your wifes CRD. It's a process of elimination now. At least you have one close by without having to buy one just to test.

gmctd · **Posted:** Sat Aug 23, 2008 9:52 pm

The electric fan comes on only above 208* with ac on and below a certain forward vehicle speed - I've wired-in a grounded spdt bypass switch directly to the lo and hi relays for testing - won't hurt a thing because ECM grounds the relays to energize them - only thing you need to do is be sure the switch is OFF when you start the engine because ECM does a continuity check on all the i\o points - if any are above or below expected ohms value during that housekeeping sweep = DTC

KeighJeigh · **Posted:** Sat Aug 23, 2008 10:14 pm

gmctd wrote:

The electric fan comes on only above 208* with ac on and below a certain forward vehicle speed - I've wired-in a grounded spdt bypass switch directly to the lo and hi relays for testing - won't hurt a thing because ECM grounds the relays to energize them - only thing you need to do is be sure the switch is OFF when you start the engine because ECM does a continuity check on all the i\o points - if any are above or below expected ohms value during that housekeeping sweep = DTC

It's a sad state of affairs that I have been on this forum enough now that I actually understand everything above except "DTC". I assume you are referring to the ECM throwing a code due to the ohm value being off...but DTC?

Why did you wire this into your system? Have you had trouble with overheating as well?

KeighJeigh · **Posted:** Sat Aug 23, 2008 10:19 pm

MrMopar64 wrote:

For sure it sounds like the viscous fan clutch is bad. I just got back from a hot trip out west, had the same problem on a car - swapped the fan clutch, problem went away. Do you have a fellow CRD driver in the area that maybe you could do this with to see if the problem follow the part or not?

OK, here is what I did: My 05 is hot. I started up my wife's 06 and let it get to 1/4 gauge. I then shut them off and spun my fan - it spun almost a full turn before stopping. I then spun the 06 which about 1/2 turn or less. The 06 is definitely stiffer. I also assume the fan on the 06, since it is cooler, should spin more freely than the one on my 05. Is this correct? I assume the hotter it gets, the more it would tend to engage the drive.

I uploaded a video clip showing my experiment. You can see it here: http://www.youtube.com/watch?v=JFEE-85zVrk

I wonder if it is covered in my 7/70 warranty...hmmmm.

gmctd · **Posted:** Sat Aug 23, 2008 10:33 pm

What gear range and what rpm do you use to get up the drive?

KeighJeigh · **Posted:** Sat Aug 23, 2008 10:48 pm

gmctd wrote:

What gear range and what rpm do you use to get up the drive?

Speed is 10-15 mph max due to water bars and neighbors. I haven't paid much attention to the gearing - although sometimes I just put it into 2nd and leave it but mostly because if I don't it can't decide what gear it should pick and often shifts between 2nd and 3rd which seems lugging it at that steep of an incline and that slow.

If I think about it.....it may be a bit more of a problem if I lug it in higher gear. Which, I assume would lead us to viscous fan clutch problem.

I can't think of a time when I saw this problem on the highway - it seems to be a slow speed, steep hill problem.

I uploaded a video clip showing my experiment. You can see it here http://www.youtube.com/watch?v=JFEE-85zVrk

gmctd · **Posted:** Sat Aug 23, 2008 10:56 pm

Lemme do some pics tomorrow, show you how to wire the electric fan for manual control, turn 'at sucker on at the bottom of the run, see how some extra airflow helps at that low speed - it's a wimpy fan, anyway, not very aggressive attack angles in the blades - got one from a Chry 300, looks bad enuff to erode the paint right off the ac condenser fins, but is a pull-thru configuration - we need similar in a push-type, one that would pull the Jeep along at 30mph when on hi speed

KeighJeigh · **Posted:** Sat Aug 23, 2008 11:00 pm

Quote:

one that would pull the Jeep along at 30mph when on hi speed

Like a swamp-boat 4x4!
The more flow the better.
Are you having trouble with overheating on your CRD?

gmctd · **Posted:** Sat Aug 23, 2008 11:08 pm

None - just intensive R&D preparations - check my sig..............

KeighJeigh · **Posted:** Sun Aug 24, 2008 5:33 am

gmctd wrote:

None - just intensive R&D preparations - check my sig..............

That mule will be quite the racehorse when done!

Pablo · **Joined:** Thu Feb 02, 2006 10:06 pm **Posts:** 1201

Sorry you are having so much trouble. My mechanical fan comes on daily at stops, but it is 110 here still. The Jeep is not close to overheating when it comes on. If you get out of the Jeep you can hear nothing but the fan roaring, it is loud. I have no doubt it moves quite a bit of air when working properly and if it is not working that would explain the overheating.

mudpup226 · **Posted:** Sun Aug 24, 2008 8:19 am

Had the same problem about a year ago . Overheating according to the gauge then going on my yearly hunting trip 100 miles into the trip away for home. Then things went south. Fan clutch went out.The fan clutch water pump shaft proceeded to move forward into the radiator took out the water pump and 38 days later. Haven't had a problem since. Parts might be a problem for these little mule? Took forever to get fixed.

Thermostat replaced - STILL HOT

Who is online