Chimaera overheats then knocking sound from engine

[tvr-badger]

For various other reasons,recently I took my 500 out for the first time this year. After a short journey the temperature got hot and there was a knocking sound from the engine. I let it cool down , checked the water level which was ok and restarted the engine. At low revs there was no knocking sound but as revs increased so did the volume of knocking. Again the car overheated.
Could these symptoms be the result of a failed water pump or are there any other likely causes?

[Sir Paolo]

Hi could be many things - how badly did it overheat before you switched off?
Generally, valve train related noises are constant and not usually affected by load (increased revs), whereas bottom end noises are.
However, before we go down that scenario, if you suspect the water pump, you could check this by removing the drive belt and spinning the pulley.
If it feels gritty and stiff, then yes the pump is failing (and you’d soon notice water loss too), there may also be play on the pulley.
But if it spins smoothly and freely, look elsewhere.

Good luck.

[Classic Chim]

Sir Paolo said:

Hi could be many things - how badly did it overheat before you switched off?
Generally, valve train related noises are constant and not usually affected by load (increased revs), whereas bottom end noises are.
However, before we go down that scenario, if you suspect the water pump, you could check this by removing the drive belt and spinning the pulley.
If it feels gritty and stiff, then yes the pump is failing (and you’d soon notice water loss too), there may also be play on the pulley.
But if it spins smoothly and freely, look elsewhere.

Good luck.

^ This. If pump has play look for it leaking right there.
The fact it got hot very soon after a short journey suggests the system is not working correctly or you have air in the system. Check your water level cold via swirl pot. Check rad hoses when it’s warming up as thermostat might be stuck closed or blockage might restrict flow back to rad. They should both get hot as soon as stat opens.
Feel if heater feed and return hoses are getting hot, set control to hot and make sure heat comes through.
Report back.
Good luck.

Edited by Classic Chim on Thursday 24th June 13:00

Edited by Classic Chim on Thursday 24th June 13:01

[Zener]

How does a failing water-pump cause over-heating exactly? (impeller intact and driven obviously) if it seized/jammed the belt would throw more likely the stat as failed shut

[Olivera]

Sounds like bottom-end gone, engine gubbed.

[Zener]

Cant comment on the noise I cant hear it

[Sir Paolo]

The gauges aren’t known for their accuracy, but what oil pressure are you getting?
If pressure is very low, it could further point to big end failure as cause of knocking, but that won’t explain the overheating, unless the sump is empty!

[tvr-badger]

Thanks for all your help and advice. Having let the motor cool down , I went to the bible on how to check on coolant level. It was fine in the expansion tank however checking the swill pot was more difficult. The slotted head would not move so I got access by taking the hose off. It took 3 litres of water to fill the swill pot (and block!!). When it was all full restarted the engine and saw that the temperature gauge immediately started to rise. With increasing revs , there was no knocking sound
.
The next job is to detect where the coolant is leaking from.
Thanks again for advice.

[gruffalo]

Can you smell exhaust gas in the coolant, my concern would be a slipping liner.

[QBee]

Big screwdriver blade sideways (i.e. horizontally) in the slotted brass plug shifts it for me