Overheating

[Baker]

See sig for specs. The temp gauge stays right in the middle of the green at 70mph, but as soon as I slow down (to 45-50mph) it overheats (REALLY overheats). Ideas?

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Baker
'84 Grand Wagoneer "B.U.F.F" (Big Ugly Fat... um...Fellow)
360,727,229, 44 & 20 (3.31s), 30x9.5
If you don't know what all those numbers mean, you shouldn't be here.

[Ralph]

Replace your radiator cap, and replace your thermostat. And check for weapage around the water pump. If those cheap fixes don't fix it, you might be in for a new water pump.

[This message has been edited by Ralph (edited August 25, 2000).]

[andy d]

B try a flushing tee. install it on the correct hter hose and back flush radiator. is the fan shroud installed?should be for max cooling.get a compressedair source and blow crud outta cooling fins from inside. how old is water pump? acid waterwill erode impellers down to nothing. how old is radiator? hard water will leave deposits that clog passages. how is fanclutch? what kinda shape are the hoses in? optimum coolant mix is 50/50.lastly a lean fuel mixture and advanced timing willmake stuff run hot. try the cheap stuff first. i tend to suspect the fan clutch, but check other stuff too. its been hot in Texas.good hunting

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'88 gwag,pure stock

[andy d]

oh,yeah radiator cap is prime suspect. thanks Ralph (doh)

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'88 gwag,pure stock

[MonsterMash]

Assuming that you are still in the same gear at both speeds the only things that change are the rpms going down and the external air flow also decreases. Decreased rpm should lead to less heat produced and the fan should be able to compensate for the reduction in external air flow. I would think that the fan mechanism (clutch in our stock set-up) is malfunctioning. All the other components mentioned will help your motor run cooler but if it just over heats at low speeds then the fan is at least partially responsible. I've had cooling problems with my rig in the past and I can testify to the problems of a malfunctioning rad. cap, missing fan shroud, and poor coolant mixtures as well as clogged coolant portals and like the guys said they are easy to remedy and will gain you some benefit.

[Ralph]

A faulty fan clutch would cause the fan to remain engaged even at high speeds, so it wouldn't have the effect of causing overheating at lower engine and vehicle speeds. The fan clutch is easy to check: if you can turn the fan relatively by hand when the engine is cool, your fan clutch is okay; if you can't move the fan, and if you hear a whirring rumble at highway speeds, then the fan clutch is bad.

I doubt this is a serious mechanical problem. Probably pressure related (i.e., replace the radiator cap). If it's a mechanical problem, then I suggest that the water pump will be the culprit. We can all pitch in to diagnose that after Baker has tried the cheaper fix.

[JERRY88GW]

Fan Clutch.

[BobBarry]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Ralph:
A faulty fan clutch would cause the fan to remain engaged even at high speeds, so it wouldn't have the effect of causing overheating at lower engine and vehicle speeds. The fan clutch is easy to check: if you can turn the fan relatively by hand when the engine is cool, your fan clutch is okay; if you can't move the fan, and if you hear a whirring rumble at highway speeds, then the fan clutch is bad.<HR></BLOCKQUOTE>

Well, that's one way for a fan-clutch to fail. The more familiar way that almost all my fan-clutches have failed has been the opposite; they stay loose all the time, so that they're never spinning near engine speed. You can test for this by taking the truck out for a drive to get it warmed up, leaving it running, popping the hood, and then watching the fan as you shut off the engine. A good fan clutch should stop spinning almost immediately; a failed fan-clutch will keep spinning a few turns after the engine is shut off. When you've turned it off and it's still hot, a good fan clutch will give a lot of resistance to being turned by hand, while a bad fan clutch will spin more freely.

It does sound like a bad fan clutch, though.

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Bob Barry<UL TYPE=SQUARE>* '78 Cherokee 4-door
* '88 Grand Wagoneer[/list]http://studentweb.providence.edu/~rbarry/wheels/

[Ralph]

Thanks, Bob. I didn't know a fan clutch could fail that way.

[Baker]

I replaced the fuel pump and took the water pump off the Jeep today. I took the water pump off 'cause there's a hole (about 1/4" square) at the top of the timing cover where it covers the back of the pump. I looked inside the pump, and found...a bolt! A F***IN' BOLT *AND* WASHER! It's about 1.5" long, .5" head, rusted together and on the threads, so it's obviously been in there a while...probably since before I got the Jeep...It looks like one of the thermostat cover bolts, but they're both accounted for and match each other (I tested the 'stat today, too). Maybe the brother of the bolt I found is still floating around in the engine...

So, what's a water pump impeller supposed to look like? The blades on mine are U-shaped -- they stick out from the hub about 1", then fold over (toward the front of the pump) and point back inward parallel to themselves about .5".

Question 2: How the he!! did it get in the water pump?

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Baker
'84 Grand Wagoneer "B.U.F.F" (Big Ugly Fat... um...Fellow)
360,727,229, 44 & 20 (3.31s), 30x9.5
If you don't know what all those numbers mean, you shouldn't be here.

[DLyons]

The AMC Gremlins put it there!
??? Really, that is a strange one.
A previous owner/shadetree mechanic was probably wandering where that bolt went.

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DLyons
84 Grand Wagoneer
360-727-229-3.31s
2" Suspension Lift
2 1/2" Body Lift(HomeMade)
Redneck Engineering at its finest!

[Ralph]

Might have fallen into the intake manifold when a previous mechanic replaced the thermostat. Anyway, good thing you found the problem. With a chunk of metal like that in your water pump, I would just assume that some damage has been done, even if you can't quite see it, and replace it. Summit racing has high capacity aluminum water pumps made by Flow Kooler for $79.95.

[Baker]

I can see the damage--I got a new pump and the blades bend 90 degrees! On the old one they were bent 180 degrees! http://www.cs.colostate.edu/~zeimet/ubb/eek.gif

Gotta go and take off the A/C compressor braket so I can get the pump on...

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Baker
'84 Grand Wagoneer "B.U.F.F" (Big Ugly Fat... um...Fellow)
360,727,229, 44 & 20 (3.31s), 30x9.5
If you don't know what all those numbers mean, you shouldn't be here.

[andy d]

hey Baker, how,d ya makeout with the hot trouble? signed curious

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'88 gwag,pure stock

[Baker]

Got a new water pump, and it seems to work. Now all I need is to fix the hole in the radiator (my uncle's friend owns a radiator shop, so I can get it done cheap).

I think the fan clutch is bad too (turn easily when hot), but I'll wait a while to replace it.

I just bought a digital camera on eBay, so I'll take some pics and post 'em in a few days.

[Manhattan]

I have a new 360, new radiator, new water pump, new 160 degree thermostat, new clutch (fan) and I can still not use the AC with the under 30 mph without overheating. This sucks - I live in Manhattan... we don't get to go over 3 mph that often.

[Coley]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Manhattan:
I have a new 360, new radiator, new water pump, new 160 degree thermostat, new clutch (fan) and I can still not use the AC with the under 30 mph without overheating. This sucks - I live in Manhattan... we don't get to go over 3 mph that often.<HR></BLOCKQUOTE>

Manhattan,
Geez, that just ain't right! Before I blew my ac hose, I could leave my wag idling in the 105 degree sun, AC on high, for at least 1.5 hrs without even coming close to overheating (I did that to test the cooling system one day). And I suspect my fan clutch is kinda weak!
Of course, now that I post this, my wag will have a meltdown.


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84 GW
360 727 NP229
Totally stock

[Manhattan]

I agree, it's not right. I have a wife and 11 month old daughter who like functioning AC - I don't mind the windows open. I did fix it though, I bought a factory Jeep replacement part - a new AC system. It came with a 2000 Grand Cherokee V8 Limited as a carrying case.

Yup, I caved. I bought a new Jeep because my old one isn't reliable.... hmmm maybe I should've thought that one through a bit more. Oh well, love the new GC.

[Dutch]

After my fan clutch went bad I replaced the entire fan assembly with the Flexi-Fan. They're available at most discount auto-shops, easy to install and much cheaper than a replacement fan clutch. Just be careful of the blades on installation they are litterally razor sharp.

Incidentally, I have beef chilling A/C and even with extended low speed pulling (hey, I like cool 4-wheeling) I have no problems at all even at 90+ degrees.

Dutch

[JERRY88GW]

I just replaced:

4 core radiator
flex fan with spacer kit
Aluminum High Vol. Water pump
180 degree thermostat
All new hoses and belts while they were off anyway.

My jeep can barly get out of the blue now. I should replace the thermostat with a 195.

But, since my engine runs cooler now. My oil stays thicker and give my better oil pressure. http://www.cs.colostate.edu/~zeimet/ubb/smile.gif

[Baker]

Another question--mine has a 195 deg thermostat. Is that what it should be? (BTW, I'm in NE TX--avg high temp this week was ~105)

Hey, a 'stat's a helluva lot cheaper than a fan clutch (which is only $20-ish--I had 'em look it up when I got the water pump)

Baker
sig removed to save server space

[JERRY88GW]

Acording to me TSM. 84 through 88 G Wags and J Trucks came with a 195 thermostat.

Jerry