M936 wrecker / NH250 water pump pouring water

[ke6rwj]

I recently changed all the belts on our m936 wrecker. This truck doesn't get tons of use but is started every other day or so. Today we used it to flat tow an m1085 LMTV about 2 miles to a storage yard (I know it's undesirable to flat tow the lmtv) when we got there the water pump on the 936 was pouring water out the bottom. It doesn't look like it's around a seal on the edges but just one spot. The truck wasn't overheating according to the guage, nor did it look or feel like it was other than the water.

I'm assuming I've gotta replace this pump, but I'm wondering if it's possible I over tightened the belt? This truck has very LOW miles, but of course they sit alot and are neglected..

Thoughts? Tips on getting a new quality pump?

-- chris

 

[simp5782]

I recently changed all the belts on our m936 wrecker. This truck doesn't get tons of use but is started every other day or so. Today we used it to flat tow an m1085 LMTV about 2 miles to a storage yard (I know it's undesirable to flat tow the lmtv) when we got there the water pump on the 936 was pouring water out the bottom. It doesn't look like it's around a seal on the edges but just one spot. The truck wasn't overheating according to the guage, nor did it look or feel like it was other than the water.

I'm assuming I've gotta replace this pump, but I'm wondering if it's possible I over tightened the belt? This truck has very LOW miles, but of course they sit alot and are neglected..

Thoughts? Tips on getting a new quality pump?

-- chris

You had to loosen the pump to tighten the belts on the eccentric so the crush seal just failed... it's a copper seal

 

[ke6rwj]

Got a better look at this issue, it's leaking from around the shaft, not around the perimeter of the pump. Also it pours out as fast as I can fill it.

 

[juanprado]

I suspect the shaft seal stuck/froze due to sitting up and destroyed itself once it had tension from the belt spinning it.
I think you will need a water pump.

Typically they are designed to leak from the weep hole.

 

[ke6rwj]

Well about a month ago I'm told that the water pump "stuck" and started smoking the belt... but when they shut it off and when restarted it was fine.. so it fits..

 

[juanprado]

Most stupid design for a water pump in history. As simp stated get the crush copper seal.
Do your research as many thoughts/opinions on what does or does not go on it.
I recommend picking up the plate gasket for the water pump and change it at the same time.

Pain in the butox that job is

 

[ke6rwj]

Yea replaced the water pump... one thing.. dont over tighten the belt.. will lead to premature water pump failure.

 

[87cr250r]

Under-tightened belts can also cause bearing failure. Bearings for rotating shafts and stationary housings are clearance fit in the housing. Without sufficient tension the outer races of the bearings can slip or rotate in the housing which causes the system to wear out and fail. Proper belt tension can be surprisingly high.