MG F : Strange waterpump behaviour..

[Slinky]

Folks, any thoughts on this?

A chap in the office has a phase 1 MG F (N plate) that has a little overheating issue from time to time.. Now, before we jump on the HGF bandwagon, he's done a little investigation and can see that coolant is being pumped through the system @ idle, yet when taking it up to 3k rpm (stationary), coolant flow halts..

Should it be doing this? (my thoughts are NO!) what could be causing it, belt tensioner gone slack or something??

Any ideas gratefully received..

slinky

[esselte]

Slinky said:

Folks, any thoughts on this?

A chap in the office has a phase 1 MG F (N plate) that has a little overheating issue from time to time.. Now, before we jump on the HGF bandwagon, he's done a little investigation and can see that coolant is being pumped through the system @ idle, yet when taking it up to 3k rpm (stationary), coolant flow halts..

Should it be doing this? (my thoughts are NO!) what could be causing it, belt tensioner gone slack or something??

Any ideas gratefully received..

slinky

Isn't the pump driven by the cam belt? I would hope that's not gone slack otherwise a cooling issue will be a small problem for your friend..

[Mr2Mike]

Slinky said:

Folks, any thoughts on this?

A chap in the office has a phase 1 MG F (N plate) that has a little overheating issue from time to time.. Now, before we jump on the HGF bandwagon, he's done a little investigation and can see that coolant is being pumped through the system @ idle, yet when taking it up to 3k rpm (stationary), coolant flow halts..

How is he actually checking coolant flow? Just looking at the bypass hose into the expansion tank doesn't really give you much idea. Overheating issues on the F are very often caused by incorrect bleeding leading to airlocks...

[MG Mark]

Mr2Mike said:

Slinky said:

Folks, any thoughts on this?

A chap in the office has a phase 1 MG F (N plate) that has a little overheating issue from time to time.. Now, before we jump on the HGF bandwagon, he's done a little investigation and can see that coolant is being pumped through the system @ idle, yet when taking it up to 3k rpm (stationary), coolant flow halts..

How is he actually checking coolant flow? Just looking at the bypass hose into the expansion tank doesn't really give you much idea. Overheating issues on the F are very often caused by incorrect bleeding leading to airlocks...

Advice above is good - it's not a great indicator as to the cause, as the speeed of the engine, and its pumping of coolant often doesn't work not in the way that is the seemingly obvious. Do the obvious tests for exhaust gases and/or presence in the coolant, water droplets on the dip stick or emulsion sludge on the rocker cover cap - those indicate or dispel whether HGF is a problem. A few questions to answer before you can really do a diagnosis:

Is it using/losing any coolant so that it that needs topping up? A low, but not critical, coolant level will affect how it flows in and out of the expansion tank, as will air locks in the system, which must be bled properly from 3 specific bleed points points, one on the radiator, one on the heater and one on a cooling hose near the distributor. Other popular causes of coolant loss, aside from HGF (particularly in the age of car) would be the failure of the pressure cap itself (very common), a leaking radiator or leaking underbody coolant pipes at the weld points on the pipes for the supporting brackets.

Other causes could be a sludged up radiator, or the water pump blades being eroded away to not a lot left. But in what circumstances is the car overheating - during higher speed running or in slow heavy traffic, on hot days or irrespective of the weather, or all those? And what is it doing when it overheats - is the judgement of overheating based just on the water temperature, what is the oil temperature gauge doing at the same time, is everything smelling hot, and is steam actually escaping in nice plumes?

But check a couple of really simple things first - a blown fan fuse (so is the fan actually working when it is needed?) and the ECU temperature sensor (which can be checked with a multimeter in situ).

See here for more detail on this and other useful pointers http://www.mgf.ultimatemg.com/hgf_diagnosis.htm

MG Mark

[PJ3074]

Hi..cooling systems are notorious for air blocks...I've just landed a nice bill on mine for new hoses from front to back, water pump, thermostat and had all belts done too. Replacement coolant going in and at garage for a long old pressure test...once done I will be adding in K-Seal just to protect my newly uprated HG. Great looking cars, fun to drive..but a total mare when you get these issues. My advice would be to get all those hoses examined, especially the steel ones (why on earth didn't they use aluminium?) for corrosion as this can be a cause for blockage and overheats. If you get all flushed through and pressure test..don't forget your K-Seal. Best £10 you'll ever spend ok

[Ginetta G15 Girl]

Put K-Seal in a K-Series engine and you are asking for it to go pop!

[GreenV8S]

I'm not familiar with that cooling system, but is it possible that there's an air lock somewhere which is being sucked down towards the pump when the water flow is enough to overcome its natural buoyancy? Look at all of the hoses which are above the pump inlet to see whether this is possible. Header tanks are usually connected to pump inlets so if the header tank is emptying and allowing air to be sucked down to the pump that would stall the pump. Another possibility is that the coolant is aerated and the pump is cavitating.

[f1rob]

had a case before where the impellor was loose on the shaft,but only slightly loose so at tickover it was like normal but as the revs increased it started to slip on the shaft

[EG6mad]

do not use K seal it just fks everything up in the coolant system. the coolant should stop when you rev it. it means the thermostat has opened. you need to fully bleed the car from the rad, the heater matrix and at the back. let the water settle for an hour with the cap of before you start it. once all done put the cap back on and re-start. if the problem carries on you have a problem with the head gasket or intake manifold.

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