Lotus Elan

Water pump flange fell off

PostPost by: Pfreen » Thu Feb 27, 2020 2:06 pm

A friend of mine‘s engine (in a Europa tcs) was toasted when after pulling the engine, it was discovered it had no water pump pulley or flange. This happened while driving 75 mph on an expressway. He described hearing a clunk, like he ran over a rock, and then two minutes later, smoke was rolling out the back and he pulled over.
I did a compression check on it and numbers 2 and 3 cylinders had no compression.
He had the head pulled and the head was warped and he is doing a rebuild.
My question is, how the heck could the pulley flange fall off, and has anyone else heard of this happening?
The car had been running fine for years.
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PostPost by: rgh0 » Fri Feb 28, 2020 5:29 am

The pulley flange is just a press fit onto the bearing shaft. If the press fit did not have enough interference then the pulley flange could fret and wear the shaft and flange and work loose overtime until it was loose enough to just move and fall off. The front of a Twincam Europa's engine is not very accessible so I suspect it would not have had a close inspection for some time. Alternatively maybe the bearing failed and this put enough load on the pulley to spin the pulley flange on the shaft until it came off

Close inspection of the water pump bearing and shaft will tell more about what happened i suspect.

I have never seen it happen, but when building engines using old pulley flanges I have found flanges that were not the right interference fit occasionally due to wear over the years.

A popular modification is to fit the pump with a larger diameter shaft and stronger bearing from later Fords and the pulley bored out to accommodate this larger shaft if this was not done correctly you could also get this problem.

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