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Trouble after water pump/thermostat - upper hose not getting hot

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Old 06-01-2022 | 09:58 PM
  #46  
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Hey all - summer update. Really didn't have any problems all winter or spring - it liked to ride just to the right of the 210 line, but didn't really get any higher than that. Drove it yesterday on the interstate, and it got more than halfway to redline from 210. I did a little research and wondered since the entire cooling system is new it might be the head gasket/head. Bought a coolant exhaust test kit, and the liquid stayed 100% blue, so doesn't look like there's exhaust gas in the coolant. Tomorrow I'll rent a compression tester and see what that gives me!
Old 06-02-2022 | 12:28 AM
  #47  
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Loosening the temp gauge at the back of the head is a quick way to burp the air out, btw.
Old 06-04-2022 | 07:46 PM
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Good idea Lawson, I didn't know that. Think that might be my trouble even with an open cooling system?

Haven't had time for the compression test yet but I'll get it done in the next week. One thing that happened during the exhaust coolant test was I had the cap off to test it and had the motor on to get it up to temp, and it overflowed some, so I had to siphon it out again once it was up to temp to drop the coolant out of the neck enough to do the test without sucking any coolant up into the tester. Is that normal or does that say I've got a problem?

Thanks all!
Old 07-15-2022 | 06:56 PM
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Hey all - just did a compression test; 3 cycles on a warm motor and tried each cylinder at least twice. Everything was in spec - here's the breakdown:

1: 150
2: 135
3: 130
4: 125
5: 130
6: 130

I just remembered that I forgot to wedge the throttle open - but if I remember correctly that would slightly increase the numbers, right? So everything still looks good then I guess.

And here's a photo of the plugs I put in last year (they've maybe seen 1000-2000 miles).




So I'm pretty happy that this motor tested well - I didn't know anything about it except that that the PO pulled it out of a 97. This was after the motor that WAS in here became garbage after the idiot PO before that put Fix-a-Flat into it instead of replacing the blown head gasket............words fail.

I'm happy to check off the head gasket from my list of maybes.......but now I am REALLY scratching my head. Do I remember that if it's running either lean or rich it can cause overheating? After replacing everything in the cooling system I'm just out of ideas! Would sure appreciate yours.

And sorry if you saw this early - sent it way before I meant to!

Last edited by Thetastycat; 07-15-2022 at 07:09 PM.
Old 07-17-2022 | 10:16 AM
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Go buy a factory thermostat.
Old 07-17-2022 | 04:10 PM
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Hey Cruiser - so I actually got three factory (Motorad) thermostats, all with the jiggle valve, and boiled them on the stove. Only one opened at 195! So that's the one I installed.

Just saw a YouTube where a guy discovered that his harmonic balancer was shot and wasn't turning with the crankshaft - since I can't find anything else wrong, maybe that's worth a shot? Lord only knows what condition this one is in.....any way to test or should I just replace?
Old 07-17-2022 | 05:52 PM
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If the balancer was that loose, it would slide off. Here's a pic for you. New radiator also?


Old 07-17-2022 | 06:21 PM
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OK - I haven't actually looked at mine but I will - just trying everything I can think of.

Here's my list so far:

New:
Factory thermostat (tested, opened at 195)
Thermostat housing
Napa fan clutch
Radiator
Hoses
Water pump
Radiator cap

Idles just a bit above 210 but when it's warm or hot (say 75 or higher) and under load, like interstate, the needle goes about halfway between 210 and redline and sometimes higher.

I flushed the system and heater core multiple times. I did a compression test and everything was within spec, and I also tested for exhaust in the coolant and found nothing. What on earth could still be causing this??
Old 07-17-2022 | 07:00 PM
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Have you recently verified that the gauge is accurate?

What radiator?

Have you verified that the pump is the correct "rotation"? Getting the wrong part in the box isn't uncommon...
Old 07-17-2022 | 07:06 PM
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Not bad ideas, Jim. I did replace the gauge, same results - and the fact that it only overheats at speed make me not think it's the gauge.

Radiator is a Spectra off of Amazon - seemed to be the best choice after researching here.

It's been long enough that I don't remember the specifics on the water pump, but the new water pump looked the same as the old one......of course now you've got me wondering. I don't suppose there's any way to verify that it's correct without taking it off again.....

Old 07-17-2022 | 07:10 PM
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OK, funny enough I still had the old water pump out back, and it looks to be correct based on the diagram I found searching here. Man......just what else could it be????
Old 07-17-2022 | 07:26 PM
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Do you have a winch or anything else blocking the grill?

Fan shroud in place?

With it only overheating at speed, if both of the above are no, I'm putting my money on the water pump being the wrong rotation...
Old 07-17-2022 | 07:56 PM
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My fan shroud is intact and in place......but I do have a winch! Here's a pic:



I had no idea that could affect the radiator's performance, but it does make sense. Can I do anything about it?
Old 07-17-2022 | 10:17 PM
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It may help to seal up any gaps around the radiator and AC condenser, if you still have it.

One thing that XJs came with was an underbelly panel that extends beyond the back past the front of the engine. This would keep air from forming a high pressure area right behind the radiator due to axle and engine. I can't say for sure that this is your issue because a lot of XJs don't have one any more, but the whole getting hot while driving fast issue gives some weight to this; it should be it's coolest at highway speeds...

Another option would be well placed hood vents, right behind the radiator, to take advantage of the low pressure area that forms at the front of the hood due to the air behind forced up and over the grill. This certainly isn't the issue, but may help reduce it.

Others with similar bumper and winch setups should chime in whether they have issues or not...
Old 07-17-2022 | 11:35 PM
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Torque converter locking up properly at speed? If not, that'll dump heat into the radiator too.



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