Coolant loss - M10

[greg124]

The latest fault on our lass's chromie is coolant loss, and I can't see where it is coming from. Checked all the hoses.
After two trips to work and back (total about 60 miles) the temperature guage goes up close to the red. On inspection the coolant level is below the top of the tubes in the radiator. Adding about 300ml brings the level up.
I could hear the radiator cap hissing, thinking that maybe the release of pressure was allowing the temperature to rise, I bought a new cap, but no change.
Another strange thing is that when I add coolant to just above the tubes in the rad, it starts coming out of the overflow pipe. Now the entry to the overflow pipe is in the neck of the rad (about and inch and a half higher than the coolant level), so I can't undertand why this happens.
As always, advice gratefully accepted.

[daimlerman]

Sounds like it's over pressurising to me...forcing coolant up the radiator neck to compress the cap's spring to release pressure....

But why?

Pump OK?
Thermostat opening properly?
Blockage somewhere...like radiator partly clogged up?

[johnl320]

You have any white sludge on the engine oil filler cap?

[greg124]

Thanks guys.
There's no evidence of white sludge on the oil side johnl.
I was thinking it was maybe over-pressurising, daimlerman, and forcing steam out past the radiator cap, as opposed to a leak.
Think I'll have the rad out tomorrow and back-flush it. Always try the no-cost options first.
Do you know whether an M40 thermostat is suitable for an M10? (As I have a good spare)

[johnl320]

No M10 thermostat is a very different beast, it sits in its own seperate metal housing connected to the bottom rad hose.

If a rad flush fails and you can confirm the water pump and thermostat are good, what you can do is take it to a garage and get them to 'sniff' the air in the top of the rad to test it for exhaust gases. This will help confrm head/gasket issues.

[greg124]

Thanks johnl.
Have now flushed the rad. Didn't get any crud out though, and the water flowed pretty freely, so I suspect the problem lies elsewhere.
I presume the thermostat must be that big metal blob with 3 hoses, one to the rad, one to the head and one to the water pump.
When I've tested 'stats before I've dangled them in a pan of hot water. Can you still see this type opening that way?

[daimlerman]

Quoting from Bentley;
For four cylinder engines,measure inside the thermostat housing and determine the change in length between cold and hot conditions.Heat the thermostat housing in a pan of water and measure as shown in fig.4-10 while monitoring temperature with a thermometer.The thermostat should open at about 80c.At boiling point the measurement should be 8mm(ish) greater than when cold.A thermostat that does not open full amount is faulty and should not be installed.

The sketch shows the 'stat in a pan with a measuring stick poking out of the top hole,and a second hole at right angles....

HTH.

[johnl320]

I have just dug out another thermostat from my pile of shite, worked fine two months ago, PM me if you are interested

[greg124]

I have now tested the thermostat, and it opens by 8mm at boiling point, and the bent elbow on the end (top) closed off, so I think we can safely eliminate that - thanks Daimlerman. And thanks for the offer Johnl.
Next question - how do I go about testing the water pump?

[daimlerman]

Bentley gives no similar information for testing the pump!

Just the expected guff that we all know about waggling the fan to check for a shagged bearing....
However,reading through the thread again,the pump must now be the prime suspect,the impeller failing to to turn on it's shaft would give all of the symtoms that you describe.

Only other possibility is a clogged radiator,sneaky buggers,radiators,you can stick the garden hose in one end and water pours out of the other at roughly the same rate and you assume it's OK,get the local specialist to sweat the core out and compare to a new one and the old looks like a twenty a day smokers lungs...

[greg124]

Thanks Daimlerman.
just the the car up to temperature. Well until the guage touched the red, then turned it off again.
The radiator cap was releasing steam, yet the radiator bottom hose was stone cold, while the thermostat was too hot to touch, and the other two hoses to it and radiator top hose all hot.

I'm beginning to wonder whether the thermostat is the problem, as if it had opened at the correct temperature (I only tested it in boiling water) the radiator bottom hose and the pipe coming out of the stat which remains in circuit when it is open should be at roughly the same temperature.

I've also waggled the water pump pulley, and there is a small amount of movement, but I'm not sure how much is acceptable.

[daimlerman]

I think, I know that's a dangerous assumption in it's self,that the pump impellor has failed...as water does not seem to be circulating.

You seem to have established that the 'stat is opening,but still getting pressure building up,so I'm blaming the pump,what do you think?


Put some piccies of your Alvis in 'Other Marques',please!

[greg124]

Just waggled the water pump pulley on my car (M40 engine) and there seems to be about the same amount of play. However, that only tells us the state of the bearing, not the impellor.
Would removing the water pump to examine it be a good ideo?

[johnl320]

just be careful not to shear a bolt removing it

[greg124]

Thanks Johnl. I'll spray penetrating fluid on them today, and get a new part ordered tomorrow

[greg124]

Just topped up the coolant again, and run the car up to temp. It seems to stabilise just below the half way mark, with a slight hiss of escaping steam from the radiator cap.
However, unlike yesterday, the bottom hose is now warm, which suggests coolant is circulating.
I am now suspecting a partial blockage of the radiator, rather than the water pump.

Any suggestions for a slightly more aggressive radiator flush than just plain water? I seem to remember there used to be somtehing called 'Radflush' but don't know whether it is any good.

[Gwynleym10]

M10's like to pressurize their cooling systems. I had symptoms that sound exactly the same as yours. In the end it turned out to be a cracked bottom end and when the engine was running, it was pressurizing the cooling system.

Can you get hot air inside the car? When you are topping up are you doing it with the fan on hot and on full?

I seem to remember what helped mine was to flush out the system (probably used 2 lots of rad flush) took the inside of the thermostate out.

If its still no better - try some K-seal.

[johnl320]

Coolant cap ok?

[greg124]

First thing I did was replace the coolant cap, Johnl. Not that that is any guarantee that it isn't faulty!
Have now flushed the system with Carplan Radiator Flush, as recommended by my local independant motorspares shop. An incredible amount of crud came out. Looked like mostly limescale.

[greg124]

Update: Haven't lost any more coolant this week, which is about 160 miles.
So it looks like flushing out the crud has cured it.
Thanks guys for your advice.

[johnl320]

Happy days