Yj over heat

a_kelley

a_kelley

mechanical fixer
Joined
Jan 26, 2010
Location
Rutherfordton
Ok.
New & clean looking rad.
Newer but old water pump
New tstat
New sending unit (supposed to match original in ohms/temp according to service manual/Mitchell)
resurfaced & checked head & new gasket
Flushed: heater, block/head, & rad.
Rad & block wasn't too nasty.
Heater hose had a turd in it.
IMG_20190713_013343594.jpg

Heater had crap in it. Flushed clear. It throws heat now..... It will run hot @ idle or 2000rpm, just keeps creeping up;;. Verified with scanner that it is indeed getting over 230. Upper hose gets hot, so I know the tstat is opening. Heater works, so I would think the water pump is ok. Upper and lower radiator hoses are not discernably different temperatures.

Thoughts? Ideas? Thinking of pulling the WP to check the impeller. If not, I'm at a loss.
 
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Mechanical fan clutch? They move a ton of air when working right. If they are not working right or get removed it causes problems.

I second your thoughts to check the water pump impeller. I’ve seen them corrode away and just not move enough water.
 
I'd be checking the water pump and fan clutch. Also that is one nasty turd out of the heater core.
 
Fan clutch is pulling air for sure. It engages harder as the temp climbs, so I don't think that's the problem. Going to pull the pump here in a while. It had been replaced but it's been some time.. and I've got no idea how long it was run with plain water in it. The turd was combustion gas deposits from the blown HG & cracked head.
 
If it was ran with just water for a while there’s a very high chance the impeller is not up to snuff. Antifreeze acts as a lubricant as well as stops the corrosion issue.
 
With that much Turd coming out of the rad. hose, I would bet the radiator needs to be rodded out.

Quick and dirty, I would pull the thermostat out and see if it can keep itself below 210.....if not, my money would be on a clogged radiator.
 
Rad is like a month or less old and appears to be clear.

Water pump impeller fine. (Removed to inspect)

Looking like fan clutch is it, heat gunned the temp coil and it didn't get any more difficult to turn.

Turning the heat on was enough to lower the temp, so definitely either airflow or the rad is stopped up, though it drains quickly and the tubes that I can see are clear. I'll swap the fan and see.
 
With that kind of crud in a hose, I have to wonder what may be stopped up in the Block? That would be my best guess, considering all the other things you've checked. Best thing I ever did for mine, is changing to the Flow Kooler water pump! But that doesn't seem to be your problem.
 
Block is clean for sure. Rad looks clean from what I can see and is newish with fresh stickers.. however I did not check pump impeller to pump body clearance, but after reinstalling the original, and looking closely at the new one, it seems the new pump is tight clearance (50-75 thou? Guess) and i seem to recall the clearance on the one I reinstalled being closer to .2-.25".. I think that would be the issue, I refilled and rechecked temps and that would be consistent with low flow.

Gauge(back of head)@ 230,
thermostat housing(IR thermo) @ 205
Top of radiator cap opening(IR thermo) @185

And no visible flow in cap opening.. pump clearance sound high? I'm going to just swap the pump at this point, but need a gasket since I used it reinstalling the old pump.. changed the fan clutch with no change. No visible flow is what's pointing me back at the pump.. I didn't see erosion on the vanes, so just threw it back together instead of looking closer at the clearance - I can't assume anything since it had a blown head gasket when it came in so any information regarding overheating from customer is worthless.
 
It's been a year since I did a 4.0 water pump but I want to say clearance on the impeller to pump body is fairly close but I could be wrong. With visible flow I'd be suspect of the water pump.
 
Have you gone back and checked that you don't have exhaust gases in the coolant? Sounds like you had to put a new HG on this....any chance the head was cracked in a cooling jacket somewhere?

I pulled a pretty roached WP out of my XJ a couple of weeks ago, and it still never went above 212.
 
Ehhhh I just remembered something else.... surely you’ve checked this but who knows.

Once had a friend whose truck ran hot and puked antifreeze. We couldn’t figure out for hours why in the world it was running hot. Turned out it had a muddy air filter and wasn’t getting enough air. Later on since I knew to check this, had a buddy’s XJ overheat and it was because the thing puked a ton of oil on the air filter=same thing.

Andddd finally, my 01’ XJ blew the head, I swapped the motor but it still overheated because the exhaust was clogged from the nasty mess from a cracked head put into the cats.

So, make sure it’s getting plenty of air in, and getting that air back out without restriction. I know it seems elementary, but all too often we are guilty of overlooking the simple so I thought I’d mention it.
 
shelby27604 said:
Have you gone back and checked that you don't have exhaust gases in the coolant? Sounds like you had to put a new HG on this....any chance the head was cracked in a cooling jacket somewhere?

I pulled a pretty roached WP out of my XJ a couple of weeks ago, and it still never went above 212.
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I had the machine shop check the new head and machine it flat. Anything is possible though.

77GreenMachine said:
, make sure it’s getting plenty of air in, and getting that air back out without restriction. I know it seems elementary, but all too often we are guilty of overlooking the simple so I thought I’d mention it.
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this I had not checked.. it's a cone filter and it's fairly dirty, I'll pull it off and see if that's not it. If it isn't I guess I'll try pulling this pump back off and look at the clearance.. it moves enough water to have heat, but I can't see flow in the radiator. (Even put some particles in to see if they moved around.)
 
77GreenMachine said:
If it was ran with just water for a while there’s a very high chance the impeller is not up to snuff. Antifreeze acts as a lubricant as well as stops the corrosion issue.
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That's a myth, don't worry about it.
What are we supposed to be lubricating with coolant in a modern water pump? If anything needs lubricating that isn't handled by bearing grease, the pump is shot and needs replacing.
 
Fabrik8 said:
That's a myth, don't worry about it.
What are we supposed to be lubricating with coolant in a modern water pump? If anything needs lubricating that isn't handled by bearing grease, the pump is shot and needs replacing.
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the seals are lubricated by the coolant.. and the corrosion of a steel impeller is real. I've seen both happen in longer term situations.
 
a_kelley said:
the seals are lubricated by the coolant.. and the corrosion of a steel impeller is real. I've seen both happen in longer term situations.
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The corrosion protection is real, yes. The seals are to keep coolant out of the bearings. The amount of lube needed for seals is minimal, although having clean coolant is very important. The spring-type seals do need lube though, yes. I did forget about the seal lubrication. But, modern water pump seals and old-style seals are very different animals.

You've already pulled the pump and looked at it, so you would already know if the coolant was an issue or not.
 
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Since I know you're no dumb ass and simple things get overlooked sometimes...
Belt routing vs model year water pump you are running? You can spin the belt the correct way, but with the wrong pump, the impellors will be pointed backwards.
Happened to me a few times when an XJ pump was placed in a ZJ pump box.
 
Jody Treadway said:
Since I know you're no dumb ass and simple things get overlooked sometimes...
Belt routing vs model year water pump you are running? You can spin the belt the correct way, but with the wrong pump, the impellors will be pointed backwards.
Happened to me a few times when an XJ pump was placed in a ZJ pump box.
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Interesting. There are reverse rotation Jeep pumps? That's a very real possibility then, especially if the pump was of unknown origin (if you didn't verify part numbers yourself, I would assume it is suspect).
 
have you pulled a freeze plug on the side of the block to see how much mud is built up around the cylinder walls?
 
Fabrik8 said:
Interesting. There are reverse rotation Jeep pumps? That's a very real possibility then, especially if the pump was of unknown origin (if you didn't verify part numbers yourself, I would assume it is suspect).
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Yup. The up to 95 model ZJ and XJ water pumps are identical. Aside from the impellors being mirror images of each other.
 
Pump matches a store yj pump.

Pulled t-stat, still runs hot just takes longer.

Different fan clutch, no change.

Pulled air cleaner off, no change.

I can see flow in the radiator with the stat removed.. 3 week old rad, been at my shop for 2/3. I'm thinking more and more about the rad being the problem.. just because a garden hose flows through it doesn't mean that it's enough flow... But it looks clear from what I can see through the neck.

Block is clear looking in from the water pump and flushed it when I flushed the heater core.
 
I had a toyota years ago, between system rust and the bars leak stop the PO added, the radiator was probably 90% clogged, everything looked normal, fought all the normal stuff you have fought before I bought a new radiator.

Taking longer to overheat with the tstat out SHOULD be a good indication the pump is pushing plenty of fluid, it just doesn't have enough cooler coolant to move.
 
a_kelley said:
Pump matches a store yj pump.

Pulled t-stat, still runs hot just takes longer.

Different fan clutch, no change.

Pulled air cleaner off, no change.

I can see flow in the radiator with the stat removed.. 3 week old rad, been at my shop for 2/3. I'm thinking more and more about the rad being the problem.. just because a garden hose flows through it doesn't mean that it's enough flow... But it looks clear from what I can see through the neck.

Block is clear looking in from the water pump and flushed it when I flushed the heater core.
Click to expand...

I’m thinking you have some heavy build up that’s not being flushed with a hose. Both in the block and rad now that you’ve ruled out other things.
 
The block is clean, I looked at that when I had the head off.. also it flowing with a hose from the outlet at the thermostat and pouring right out the front where the water pump goes, and there's -no- crud whatsoever visible in the block, I'm near certain I can rule that out. (You can see all the way to the back of the block with the pump removed.)

I think I'm going to toss a known good rad in it and see.
 
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