Bleeding coolant system

neilly · Oct 20, 2019

My 90 300tdi, runs at 96C on a private runway at 80 ish. Normal tootling about it sits at 92.

Cheers

ivancrx · Oct 20, 2019

Well I have just purchased a new brass and copper radiator so if nothing else I can rule the radiator out of the equation.

Got to love spending money on the thing.

flat · Oct 20, 2019

I inly day as I had endless trouble with mine with a copper and plastic rad, recored the original and it was fine immediately!

ivancrx · Oct 23, 2019

Well that didn't work, £250 on a new radiator and still no difference.

flat · Oct 23, 2019

oh wtf.

is the system holding pressure when hot?

so just to refresh:

stat - checked twice, both stats good and fitted right way round with joggle valves

- rad, swapped for new quality item

- gauge is a durite one and corresponds with the IR gun

- water pump is working and shaft is firm, vanes all okay and it pumps alright

- matrix okay

- pipes okay

whats in it? coolant or water?

I am at a loss, trying to imagine it in my head is giving me a headache!

ivancrx · Oct 23, 2019

flat said:
oh wtf.

is the system holding pressure when hot?

so just to refresh:

stat - checked twice, both stats good and fitted right way round with joggle valves

- rad, swapped for new quality item

- gauge is a durite one and corresponds with the IR gun

- water pump is working and shaft is firm, vanes all okay and it pumps alright

- matrix okay

- pipes okay

whats in it? coolant or water?

I am at a loss, trying to imagine it in my head is giving me a headache!

I am now using a Tim gauge as I swapped this with the durite one to just try something else, i am only running water in it at the moment.

Water is pumping round fine.

There isn’t anything else I can change.

Mo Murphy · Oct 23, 2019

Personally I would not bother about it until you have driven it on the road and see how the temperature behaves whilst driving, with airflow through the rad.
Like neilly, my 200 runs at 92°C, getting up to about 96°C when the thermostat fully opens if pushed hard. Measured on an electric VDO guage and sender.
HTH
Mo

kermit_rr · Oct 23, 2019

Yes, i think I'd be driving it from cold at reasonable revs to keep the flow. Keep an eye on the durite gauge.. see how it goes

ivancrx · Oct 23, 2019

I am going to try and get an mot on it at the weekend and see how it runs.

Nothing else to lose.

Interceptorxj · Oct 23, 2019

So it isn't actually overheating /pressurising or spewing its water out?

flat · Oct 23, 2019

HAs it just been sitting idling as opposed to being driven?

zeaphod · Oct 24, 2019

I feel your pain, this is one of those odd ones. You do seem to have considered everything. Just to confirm - have you tried running it without a thermostat? Is it actually running as hot as the gauge says? - over 90deg you will have trouble holding onto the hoses. Just one more thing - if it only overheats when being driven (as opposed to sat idling) - your brakes might be binding - it's a bit of a stretch, but worth checking.

ivancrx · Oct 24, 2019

flat said:
HAs it just been sitting idling as opposed to being driven?

No is is sitting on the drive at the moment, but prior to replacing the chassis you could see the temp drop on the gauge when it got to 88 degrees, now it just keeps rising until I turn it of at 100 degrees.

ivancrx · Oct 24, 2019

zeaphod said:
I feel your pain, this is one of those odd ones. You do seem to have considered everything. Just to confirm - have you tried running it without a thermostat? Is it actually running as hot as the gauge says? - over 90deg you will have trouble holding onto the hoses.

I have tried without the thermostat and it is the same, tested with an IR thermometer and it reads the same as the gauge, can't hold on to any of the hoses as too hot.

zeaphod · Oct 24, 2019

Thanks Ivan, you really do seem to have covered all the obvious things. Not the rad, not the pump or thermostat. It's odd, I can't get mine near 88 degrees unless I thrash it. I don't understand how your engine is generating so much heat. Someone must have had the same symptoms.

zeaphod · Oct 24, 2019

Logically, that rad should be easily capable of cooling the engine. I can't see how it can be anything but a problem with the water flow, the only other thing I can think of is that the engine has started to generate a lot more heat since the rebuild. Did everything go OK with the engine rebuild? Could any engine bearings be binding?. If you take the belts off and the glow plugs out you should be able to turn it over easily with a ratchet on the crank nut. I'm clutching at straws on your behalf

flat · Oct 24, 2019

its a good suggestion, could an internal water way be blocked or something?

ivancrx · Oct 24, 2019

zeaphod said:
Did everything go OK with the engine rebuild? Could any engine bearings be binding?. If you take the belts off and the glow plugs out you should be able to turn it over easily with a ratchet on the crank nut. I'm clutching at straws on your behalf

The engine turns over fine with no problems at all with binding, this is using the crank nut.

I am just going to get the MOT on it (hopefully it will pass), and then try running it and see what happens.

ivancrx · Oct 24, 2019

flat said:
its a good suggestion, could an internal water way be blocked or something?

Water runs around the system no problem, had a hose on the heater hose and flushed it through no problems, so I wouldn't think a waterway was blocked.

Hicap phill · Oct 24, 2019

Does the temp keep rising past 100 or do you turn it off?
Header cap on or off when you testing?

(Our classics goes over 100 & then cools real quick. If they get to 110 we turn them off)

sorry for more questions but we are all trying to help

Bleeding coolant system

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