Water pump or thermostat

[derjac]

My Marlin has suddenly started to overheat. The engine is the morris 1800.

Not sure if it the Thermostat but can't get the thermostat housing off as I think it has corroded arround the studs and I am trying to get a replacement before I damage it in the removal process.
However it may be the Water pump. The engine gets hot then fills the expansion tank, which then overflows. Would this happen if the water pump was not working?

Grateful for suggestions

Derjac

[dogoncrazy]

Re: Water pump or thermostat

Is the fan belt tight enough to drive the water pump?
Does the top hose get hot when engine is up to temp, if it does then the thermostat should be ok.
Unlikely that the water pump is unserviceable unless its leaking coolant -seals can fail but you should see evidence ie fluid dripping or worse from beneath the pump.
Radiator could be silted up-remove both top and bottom hoses and flush through with garden hose, you should have unrestricted flow.

[b_caswell]

Re: Water pump or thermostat

I would bet on the thermostat failing shut. Try drizzling pepsi cola over the studs of the stat housing to freee it.
I think I remember someone having a water pump fail when the impeller fell of.
Lastly (but hope not) the head gasket may have failed.

[derjac]

Re: Water pump or thermostat

Thanks for the help guys.
I will give the radiator a flush through as suggested.
I will also try the cola trick I,l try anything to shift the thermo housing.
I dont think it is the head gasket as there is no steam from the exhaust and the oil is still thick.
It is funny how the coolant is expeled through the expansion tank.
Thanks again

[cameronfurnival]

Re: Water pump or thermostat

have you checked the pressure cap? Might be a simple case of it failing :-)

[derjac]

Re: Water pump or thermostat

Good news. Having sourced a replacement housing from the MGB specialists I resorted to the Birmingham spanner and finely removed the thermostat.
The thermostat does not open when placed in Boiling water so I think that is the problem.
On a slightly different topic I note that the head has an 'A' cast onto the surface. does this mean it is an A series as I had thought it was a B series coming from a 1972 car.
Thanks for all your help

Derjac

[CABRIOBOB]

Re: Water pump or thermostat

The B-Series 1800cc engine has the letters 18V incorporated on the serial number plate just below the cyl head behind the alternator and has the number 1800 cast in the block in front of the fuel lift pump.

[derjac]

Re: Water pump or thermostat

Thanks for that Bob. Yes it does have 18V on the plate. I will look for the 1800 tomorrow.

Derjac