XJS ( X27 ) 1975 - 1996 3.6 4.0 5.3 6.0

Water leak

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Old Feb 18, 2018 | 05:22 PM
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Default Water leak

i have a coolant leak. Tiny rivulet coming from the bottom of the crank. I cannot see a leak at the water pump, but I’m assuming that. No way for coolant to come from anywhere else right?

Engine cold fill the low coolant in the center coolant fill. Very tiny sucking sound can be heard from water pump area. Drips ensue. Pump is properly torqued.

Im thinking this Welsch part is a great value.
Water pump
 

Last edited by JigJag; Feb 18, 2018 at 05:25 PM.
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Old Feb 18, 2018 | 07:16 PM
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Yes, probably the pump...but there are coolant hoses above the pump that might be leaking....and the path of the drips can take unusual twists and turns.

Looks like a good deal on the pump, yes

Cheers
DD
 
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Old Feb 18, 2018 | 08:09 PM
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Originally Posted by Doug
Yes, probably the pump...but there are coolant hoses above the pump that might be leaking....and the path of the drips can take unusual twists and turns
Cheers
DD
Everything visible is dry. Only the bit directly above the crank is obscured. Must be there.
 
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Old Feb 18, 2018 | 08:44 PM
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Originally Posted by JigJag


Everything visible is dry. Only the bit directly above the crank is obscured. Must be there.
Can you pressurize the system to see where it sprays from? On my car there is a small hose at the top of the filler neck on the expansion tank - might have to buy a plastic fitting but it works well for testing. Auto store will have coolant dye for for a blacklight to if that fails.
 
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Old Feb 18, 2018 | 09:06 PM
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Originally Posted by VancouverXJ6
Can you pressurize the system to see where it sprays from? On my car there is a small hose at the top of the filler neck on the expansion tank - might have to buy a plastic fitting but it works well for testing. Auto store will have coolant dye for for a blacklight to if that fails.
I can run it. It’s a very small leak. Drip, drip, drip. Even when under pressure, hot. Almost surely a leak at the gasket dead bottom of the pump. It’s dry everywhere else (can’t check that bottom spot) but bottom of the crank is dripping. Back side of crank bearing has no water jacket right😳?
 
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Old Feb 19, 2018 | 08:59 AM
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Originally Posted by JigJag
It’s dry everywhere else (can’t check that bottom spot) but bottom of the crank is dripping. Back side of crank bearing has no water jacket right��?
Correct. Sounds like the pump gasket or the actual pump spindle seal. BUT, it is worth carefully checking the bottom hose where it joins the pump inlet. Leaks round here are very common and might well give you those symptoms. But if you can get a bit of paper tissue up to the pump bottom (ie above the bottom hose join) and find out if it is wet right there, then that would confirm it is a pump leak.
 
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Old Feb 19, 2018 | 09:20 AM
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You need a cooling system pressure tester. Nothing like being able to go 5 psi above the normal pressure to find all those leaks, and they're a hell of a lot easier to find when the engine is not running, and it is cold.

Mine is a Mityvac MV4560.
 

Last edited by Mark SF; Feb 19, 2018 at 09:23 AM.
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Old Feb 19, 2018 | 09:38 AM
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There should be a hole on the pump shaft for if the seal fails but as doug said, the hose above tends to easily leak. Try to do a very good job drying and check again, especially if you have a pressure tester. Add dye if necessary.
 
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Old Feb 20, 2018 | 04:41 PM
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On my AJ6, had a similar problem, small leak, hard to diagnose, even pressurizing system.

After eliminating everything else, coolant was coming from the weep hole on the water pump, which indicated a bad seal. With 137k miles and who knows how many brushes with overheating, not surprising.

Solution: new water pump ($75), which also let me renew some seals, hoses, and gaskets. No leak, no worries since.

The V12 water pump should not me that much different, and the solution is the same: rebuild or replace it.

Padre
 
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Old Feb 20, 2018 | 06:08 PM
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You could also get an electric pump for a similar price.
 
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Old Feb 21, 2018 | 02:09 AM
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Hi

I had a similar problem, which turned out to be a leak around the 'Banjo Bolt' underneath the 'Closing Panel'

Where 'Water' would run (out of sight) along the Top of the Rad and then drip down, so might be worth checking that

As it took me forever to find out where the leak was coming from



Water was leaking from the 'Banjo' under the Closing Panel and running across the Top of the Rad and then dripping down
 
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Old Feb 25, 2018 | 07:39 AM
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New pump arrived Friday so yesterday I removed the old pump cleaned up all the surfaces and installed the new one. My rad drain worked perfectly and I was even able to get a Poly line to stay on it so no spills! Amazing.

The return pipe pipe was in pretty poor shape, peeling paint and rusty in a few spots. When I got it off it was worse at the attachments. Seems a lot of fluid gets trapped between pipe and hose. Wire wheel and new coat of enamel fixed it up sufficiently for me. Baked the enamel in overnight so I’ll be reassembling today.

Better.


I have a pair pair of T-stats rated to open at 78C. Listed as “summertime thermostats” by one of our vendors. While I have her dry would be the time to swap em if I’m going to.

Any opinion on lower temp stats for the hot months? Not looking to fix a problem here, she doesn’t overheat, but I also don’t have a fear of her running too cool here in the southern US.
 
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Old Feb 25, 2018 | 12:43 PM
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Replumbing the water pump went as well as can be expected. I’m very dirty and have several good scratches, but no leaks!

For anyone wondering, the bearing was worn. Noisy, I didn’t notice until the new quiet one, and leaking.
 

Last edited by JigJag; Feb 25, 2018 at 04:41 PM.
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