First a quick report: the GMB 125-6030 water pump I installed three months ago and drove maybe a thousand miles on started leaking, with coolant flowing out of its weep hole. The engine is cooling fine with plenty of heat from the heater, so I'm assuming this was a very early failure of an internal seal.

A lesson learned for diagnosing mysterious coolant leaks down the front of the engine is to run the engine until the leak starts and then quickly shut it off and remove the water pump pulley to check the weep hole hidden under it.

Anyway, when I went to look up the torque specs for the water pump bolts I ran across this thread on the XJ8 forums. Apparently there were both revisions to the bolt length AND worries about snapping off bolts over there, with shop manuals warning not to use bolts more than three times.

I can't find mention of either on these XK8 forums even though both cars seem to use M6 bolts torqued the same.

Has anyone here had worries about snapping bolts when used more than thrice?
Did XK8 move from the M6x50 JFB10610B to M6x55 AJ88674 as well?

When I replace this pump I'd sure hate to face extracting a broken M6 for want of $5 worth of new bolts.

 

When I replace criticaI parts, I use OEM ones so I don't have to do it over. This goes for alternators and water pumps. Rebuilt stuff is not dependable, some good, some lousy. Reusing bolts should be no problem with a water pump, although I like to use anti seize on them. A corroded water pump bolt is a real bummer.

 

The Heritage site shows JFB10610B as superseded by AJ88674, although still described as M6x50. They're also >$4 each

JTIS torque figure is 8Nm + 90°, which I think means it's a stretch bolt and might explain why some are snapping after they've been reused a few times. Must admit I missed the 'torque to yield' when I did the R&R so mine are just torqued to 8Nm. Hard to imagine that low figure shearing a m6 bolt under normal circumstances, but I would have renewed them had I done my research properly.

I agree with oldmots about using antiseize in this location, although that's another popcorn session re its effect on torque figures

ISTR the Delco pump I used had a hole on the top of the shaft. Thought that was from old skool where you could add a couple of drops of oil as periodic maintenance.

 

Huh, even with +90° I wouldn't expect 8nm to torque to yield.

Well, if those XJ8 guys are on to something plausible with this, then maybe they also know what they're talking about with the spec for steel grade 8.8. That's pretty easy to find.

Tomorrow the replacement water pump arrives, and I'm leaning toward changing out bolts for some generic grade 8.8 bolts I know I have on hand.

From my reading last night, water pumps these days have these weep holes to let water out through a failing seal instead of oil in through the seal where it might contaminate coolant, and to give drivers warning that the seal is in the process of failing. At first I thought that was a pressure relief and my coolant was somehow going overpressure, but a variety of websites lead me to think the hole really is mainly about showing and dealing with the failing seal.

 

99% of the time, the failing pump seal, which is allowing the "weeping", is caused by the bearing going out.

Z

 

AJ88674 what is it m6x50 or m6x55???

 

I know this post is old, but I wanted to include a note about weep holes in water pumps.
A little coolant leaking from the weep hole is not a sign of failure! It's how the water pump is designed to work.
Without the weep hole, coolant would back into bearing housing, and wash out the grease, leading to bearing failure.
As long as your pump is operating efficiently, a little weeping isn't anything to weep about! (small joke there....very small)
Here is a little video from a water pump manufacturer that talks about the weep holes and their purpose.

 

With all due respect to the expert at Gates, if you ignore a weep hole dripping at some point you will experience water pump failure. A small leak as described by the Gates rep inevitably leads to a larger one. Have I ever seen a small leak stay that way ? No. They get progressively larger. It may take a few weeks or months, but the drip becomes a drip drip drip.

I’ve replaced hundreds of water pumps in the past 50 years that had totally failed by seizing up or bearing failure by disintegration. Every one has signs of coolant coming out the weep hole that was ignored by the owner.

Conversely, when the weep hole is 100% dry of coolant, the pump operates perfectly..

perhaps videos like this is a good strategy to counter warranty claims long enough so the pump is out of warranty, hmmmm ????

Customer: my pump is leaking out the weep hole

Gates rep: that’s not a problem, it’s part of the design

Customer: grrrr… grumble grumble, well OK.

Gates rep: (a few months later) you’re back, how can I help you ?

Customer: that leaky pump seized up. I want to make a warranty claim.

Gates rep: let me check your receipt. Sorry, your warranty expired yesterday….
Next please.

Customer: grrrr…. Grumble grumble..”

I think I’ll believe my lying eyes this time.

Z

 

Totally agree with zray on this one!
Water punps with weep holes has been around for 40-50 years and has one purpose; tell you that the internal seal is leaking.
The weep hole let the coolant escape so that you will discover the failure of seal BEFORE the bearing gives up.
Very often the seal fails because the bearing has got some slack in it.
And cars "today" has a totally sealed coolant system that runs with a specific pressure. The pressure makes the boiling point higher.
With a leak your pressure will be lower and so will the boiling point.
There is only one answer to this; If your car has a leak - fix it!