Imo000

Pulled the pump today and the pump did contact the block. However it is extremly minor. I've compared it to the spare engine and there is barely a lip where the impeller touched the block. It's not even close to what I've seen in other threads where the block was actually machined out by the cast iron impeller. I think I'll put some playdoh on the replacement pump impellers and see how much the gap is. Anyone knows what the aceptable clearance between the impeller and the block is?

Mrmerlin

you got lucky,
put a new pump and gasket on it and run it

Iwanna928

Wow nice save. Looks like you will be OK. Good thing you are handy and doing the work yourself or this would have cost some money.

Are you looking into ED's new pump being sold by Roger by any chance?

Good luck! Looks like you will be driving in no time!

PorKen

Water pumps don't just go bad all-of-a-sudden...

I wonder if a (5/16, 8mm) glass fuel filter in the 'burp' line from the coolant bridge would show ground aluminum (or other coolant issues)?

I think I might put one in place of my leaky coolant pressure sensor to what it collects...

Lizard928

how many miles on this pump?
Was in a rebuilt?

blown 87

Yea, the old style lasso's can and have done just that, mine did in less than 3000 miles from new.

Imo000

Well.... uhmmmmmm I'm going to get flamed for this but so be it as I won't lie.

Bought the pump 10 years ago, used, off e-bay for $25. I was laid off and had limited funds to get the project finished. Bought the car with a failed WP (looked just like mine does now) and the T-belt jumped, bending all the passanger bank valves. The idea was to put this used pump on with a new belt and next time get a new pump too. The miles on this pump were not that much since I had it, maybe 10K.

Lizard928

I am suprised noone had asked that yet....

polecat702

Irme, you must have a lucky horseshoe up you're rump.

blown 87

I have measured a fresh volute with a couple of different water pumps and found the clearance to be up to .090 with a new lasso, less with a rebuilt pump from mark, about .030 IIRC.

I think the specs Greg wanted when I did the block repair was .020.
All of this in in inches.

Tails

The clearance between the impeller and the conical recess in the block should be as close as possible to prevent flow-by.

Usually centrifugal pumps have an impeller incased by two side, like a ventlated disk brake and the water seal is obtained by seal ring located in the pump casing.

As the impeller in our cars is only encased on one side and the conical shape in the block is in fact the other side of the impeller, so minimum clearance is required for maximum efficiency. Before setting to minimum check that there is no axial end play in the bearing as this could effect the clearance required.

The clearance can be adjusted by using different thickness of gaskets which can be made by yourself. All you need is a pair of sharp sissors and some wad punches. To get an outline on the jointing smear some oil on the WP joint face and place it on the jointing and you will have a clear outline to cut to.

The volute is spril scrol like a gastaropod's shell (sea shell) and can be clearly seen in post 46, in the WP casing and correspondingly in the engine block, that spirals out from the pump impeller.

Tails 1990 928S4 Auto

GregBBRD

Agreed.

New factory pumps on undamaged blocks consistantly measure .019" to .020", using a factory gasket.

FredR

Imre,

A few observations here:

1. I have always had the impression from the likes of Rennist that generally the 16V motors do not tend to bend valves if the TB goes- clearly not the case unless your motor is the 32 valve 86.5 motor?
2. I am sure you feel bad enough without the need for anyone to jump all over you. I am sure a big lesson has been learnt about water pump economy.
3. I dare say that no matter what one does sooner or later most owners will face a problem with TB/WP- no matter what you do there remains an element of unpredictability. I certainly feel that Roger's new water pump is worth considering.
4. My personal recommendation is to replace the WP/TB every 60k km [approx 40k miles] or more importantly, every 5 years and at the same time do the water hoses and clean/flush out the radiator. Change the coolant every two years or so just to replensish the anti corrosion chemicals/clean the system.
5. When the water pump fails you do not have much time to react. I guess the lesson here for other owners is "ignore the timing belt warning light at your peril". On the two occasions I have seen this light come on I immediately stopped the car and opened the bonnet to take a look at things/sniff down the cam belt vent towers to smell for any burnt rubber. If there is none, I presume the belt simply needs adjustment. Needless to say, if burnt rubber can be smelt- stop the engine immediately.
6. If the timing belt has jumped a cog you might consider testing compression just to make sure no valves were bent.

Best wishes for a speedy and cost minimal recovery.

Fred R

M. Requin

Interesting idea! I might try that to, just for the heck of it.

Imo000

Fred,

It's a 32V engine and all is well.

I was in too much hurry to get the car ready for Hell that didn't have time to take any pics. I took all the necesarry steps to make sure everything was put together as it should. This included wire brushing each bolt and so on.

Buttonned it up half an hour ago, go it running 30 min before that. Runs as smooth as it did before the WP incident.