Lotus Elan

Seized water pump ?

PostPost by: wobblyweb » Sat May 02, 2020 8:22 am

My car is overheating. Temp just rises with no cooling at all. The stat is opening and the radiator is not blocked.
Top of the rad is hot bottom is cold. I suspect no water is circulating. Heater blows cold.
I have removed the fan belt and the water pump turns but not freely. Can they seize..
The pump does turn when the engine runs at low revs but I suspect slips.
Should it spin a few turns by hand or is it tighter than that.

Thank you
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PostPost by: alan.barker » Sat May 02, 2020 11:00 am

Have you removed the bottom Rad hose yet to see if it is not blocked with a Jelly type product.
I had this problem on a car and i think it was caused by some reaction they caused like a Jelly in the Pump :shock: :shock:
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PostPost by: wobblyweb » Sat May 02, 2020 12:16 pm

Hi Alan, water is running freely from the top hose through the rad and out of the bottom hose.
I can only think the pump is not circulating the water.

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PostPost by: benymazz » Sat May 02, 2020 3:12 pm

It's tough to describe how stiff something is, but I'll give my best attempt. My water pump when new had very slight resistance to turning but spun freely, if that makes sense. With coolant in the cooling system, if I spun it as hard as I could with my hand it would only turn maybe 1/4-1/2 turn once I let go. With a more worn water pump maybe it would get 1 to 1-1/2 turns before stopping.

That's a poor way of measuring anything meaningful though. I would be more concerned if when you grab the water pump pulley and try to move it up or down or side to side there is an undue amount of play. If there is too much play it is possible that the impeller of the pump is grabbing the insert in the timing chest and causing binding HOWEVER if there was enough play for this to happen I would expect you to be dumping coolant out of the front of the timing chest.

If when the water pump was assembled the proper clearance between the impeller and the insert was not achieved (.025-.030" I believe), then it is also possible that the impeller is binding on the insert.

There are more possible failure modes of course, like the impeller coming loose on the shaft, or a piece of debris interfering mechanically somewhere, but they are extremely unlikely.

Even though you say that the thermostat is functioning correctly you have all of the symptoms of a bad thermostat. I would experiment by removing the thermostat entirely and running it and seeing if it overheats still.

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PostPost by: englishmaninwales » Sat May 02, 2020 3:20 pm

Sounds like an airlock. Have you refilled recently?
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PostPost by: wobblyweb » Sat May 02, 2020 4:18 pm

It will not spin not even a quarter of a turn and there is no up and down movement or leaks, It does have a resistance to turning. The stat must be opening as the top of the radiator gets very hot.
I think unfortunately it is an engine out job.
Don't think its an airlock problem, but whatever the pump is not correct so will need changing anyway.
Happy days.

Thank you for your help
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PostPost by: alan.barker » Sat May 02, 2020 4:39 pm

I would remove Rad and back flush to be sure of flow in Rad first.
If you remove Engine i would change all Core Plugs and while Core Plugs removed flush Block. Also flush Heater Mattrix.
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PostPost by: mbell » Sat May 02, 2020 5:57 pm

I would back flush the radiator and engine. Just requires removing thermostat and bottom hoses and a hose pipe.

Would be looking for gunk in the coolant, that it flowed well, and how easily the pump spins with no coolant in there.

I'd also flush the block while there by removing the drain plug behind number 4 exhaust manifold.
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PostPost by: Mr.Gale » Sun May 03, 2020 5:33 pm

Or you can do this. :D https://www.youtube.com/watch?v=I9No_RTRGIE&t=8s
The other benefit is increased power.

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PostPost by: wobblyweb » Sun May 03, 2020 8:38 pm

The engine is almost out. whatever the problem is the water pump is far too stiff. I can only just turn it.
The pipes and radiator are all clear enough. I will report back when the pump is out. Good call for the core plugs I will change them and also flush everything out.
Thank you for your help
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PostPost by: wobblyweb » Thu May 07, 2020 1:58 pm

Engine is stripped and I have found the water pump impellor is loose.
It looks like it has loosened enough to move and then jam on the block causing the pump shaft to spin inside.
The impellor pulled of the shaft by hand and now the pump spins freely. I cant understand how it is loose Its been on the car a few years but not done many miles.

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PostPost by: alan.barker » Sun May 10, 2020 8:49 am

Was the Impellor a press fit on the Shaft.
Was the clearance set correct.
Is the special Wire Clip in place to stop Bearing moving in Alloy Front Cover.
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PostPost by: wobblyweb » Sun May 10, 2020 8:52 pm

I'm certain everything was assembled correctly when I last rebuilt it. The impellor was pressed on and with the correct clearance.
Just stripped the water pump from the cover and inspected it, the impellor spins freely on the shaft and it does have a mark where it has jammed against the block. I did have a problem last year when the car would run with correct temperatures but after a long run then stop for a while it would overheat. After letting it cool everything would be fine again.
I don't know why but I guess getting the car really hot must have expanded the impellor and made it slip??? until finally once too often it came off all together.
New water pump on order. I had forgotten how big a job it is to change.
On a slightly different subject, on removing the sump I found the spring from the front cover oil seal snapped and lying loose, that explains the oil leak. :D
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PostPost by: nmauduit » Mon May 11, 2020 7:38 am

wobblyweb wrote:I don't know why but I guess getting the car really hot must have expanded the impellor and made it slip???

I rather think the water pump was getting out of whack caused the car to overheat more and more (provided the conditions for overheating were present)

as for the pump failure itself, if it was assembled properly (including spring, clearances etc) is it still possible that corrosion of the casing and/or previous cold pressing in and out of the bearing caused metal removal where the bearing holds, not leaving enough material for a strong fit (there is not much for the bearing to grab onto to begin with). It is recommended to use temperature difference to assemble the pump (casing in boiling water and bearing in the freeze box), with a setup to do it square and right the first time.
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PostPost by: alan.barker » Fri May 15, 2020 8:41 am

Please don't forget to change the Core Plugs and while Core Plugs out give Block water ways and good clean.
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