Water Pumps


New member
I have a 1986 Vanagon Westfalia with water pump problems. Since October of ’09 I have gone through 7 different pumps. Some pumps have gone a few thousand miles, some have made it less than 100. The pump will drip for awhile before bursting. This summer I drove halfway across the country with it dripping, but it never burst and I eventually had it replaced. Another time I had the pump replaced, and the new pump burst within a week of driving around town.

Pertinent information:

I have a mechanic that I trust. He has done a lot of work for me, and everything else has been repaired on the first try. He guarantees his work, so at least I have not had to pay each time, but I miss having a reliable car.

He has used different brands of pumps, and all have been brand new.

He has promised me that the belt is on properly and the pulleys are fine.

He has done compression tests on the coolant system, the heads and the head gaskets, and all check out.

One of the pumps was replaced by an out-of-town mechanic, when a pump began leaking on vacation. He said everything looked fine, and I should not have any more problems. I made it 200 miles before that pump blew.

I seem more likely to have pump problems under extreme conditions, like going up a long, steep grade (I live in Idaho; we have lots of them), really hot weather with the AC on, or cold weather with the heat on. This could be just a coincidence, though.

My mechanic now wants to take the engine out so that he can do a more powerful compression test. I think this would be expensive and a waste of time.

I wonder if the AC or any other coolant fan could be shaking the engine compartment so much that it could be throwing the belts or pulleys off.

There really is no constant in the pump problem. It is a total mystery and I am at a loss. I am even thinking of putting myself through the embarrassment of calling “Car Talk”.


New member
We would need to know what the definition of a "...burst..." water pump is. I am assuming that coolant is leaking along the driveshaft, past the seal and out into the engine bay. If that is the case I can see the "dripping" scenario but need to know more about the "burst" portion. Does the shaft break? Bearings seize? Housing break? Leak between the pump housing and the pump body?

Your comment "I seem more likely to have pump problems under extreme conditions, like going up a long, steep grade (I live in Idaho; we have lots of them), really hot weather with the AC on, or cold weather with the heat on." suggest that the the pump seems to have issues when your cooling system is working the hardest. My thought would be a bad head gasket or cylinder head that allows combustion pressure into the cooling system when the conditions are just right. I would guess the temperature has to be just right for the issue to happen. The chances of your mechanic being able to replicate the temperatures your engine is under while climbing a hill (for example) are unlikely. There is a test that some shops can conduct on the cooling system that can highlight if there is evidence of combustion gases in the coolant. This should be done so that the cylinder head joint can be either confirmed or ruled out as the root cause. If your mechanic has access to an exhaust gas analyzer that might pick up combustion gases if put in the coolant tank (but not in the coolant).

I've seen cracked heads that work OK under all conditions until they get hot and then issues can occur. There are not a lot of other root causes available that could cause the water pump life to be shortened so drastically but the evidence would be the failed pump. Please take some pictures or describe the failure as best as possible or ask your mechanic to see if there are combustion gases in the coolant.


New member
The dripping I referred to is fluid coming out of the weep hole of the pump.

By burst I meant that the shaft breaks.

I knew that I forgot one test, my guy has an exhaust gas analyzer. There was no evidence of any combustion gases in the coolant.

The test my mechanic wants to do would be in a machine shop, which he said would best replicate the extreme conditions.

I hope this helps, and thanks for the quick reply.


New member
Thanks for the information. If we can rule out the exhaust gases in the coolant then the only other issue I can think of is the water pump impeller coming in contact with the cylinder block. This could only be seen with the pump removed so I would have thought your mechanic would have noticed any contact marks if that were the case. I know we're far down the replacement trail but do you (by any remote chance) have the original pump? (The vehicle made it 13+ years so the original might have some clues as to why this batch of pumps is not holding up.) I know you have said you tried different manufacturers but have you tried a water pump from your local VW retailer?

Is there any evidence on the shaft (either side) that it was rubbing before it broke? This would identify if the pump shaft was having any side load on it before it failed. If it does, then we would need to look at the fan belt loading as being the issue.

I doubt the loading would break the shaft and would guess the belt would slip around the pulley if the shaft was stuck for some reason but cannot figure how the shaft would break in two. I've been a mechanic for 27 years and rarely seen a water pump shaft break let alone multiple pumps on the same engine.

You might want to have a different mechanic install a water pump and see what light (if any) he can shed on this. Sometimes a fresh set of eyes can notice something that another cannot and that might unlock the mystery. If the results are the same then you can rule out installation issues but you might just get lucky and have no issues.


New member
Belt Tension

The measurement for proper belt tension in Bentley is mm deflection. I've never understood how hard you should push or how to measure the deflection when your thumb is in the way, so I bought a Krikit II Micro-V belt tension gauge. It makes a satisfying click when it measures the pounds of tension. Unfortunately, I can't find the specifications for tension in pounds. Does anyone have those specifications?

1985 Camper