have you got the thermostat round the right way ?
Hello brains trust. So on a td5 here.
So I recently replaced head gasket and at same time did all the coolant hoses, radiator and water pump.
All seemed good but now I think the coolant is over pressurising. I'm losing small amounts of coolant at various points after a drive. I've tried a different expansion tank (although not new) and that didn't change anything.
Other strange thing is the radiator is staying cool with engine running (coolant measured at 92 degrees) but minute I turn engine off the radiator gets hot. I guess it's flowing in reverse. It's a relatively new thermostat but it was off for a while when head gasket changed, although I kept it in a bucket of coolant. Engine not overheating.
Apologies for the essay, hope you're still with me. Any ideas?
I'm thinking thermostat but would have thought it would overheat if that was it. And would that cause the pressurising?
Anyway over to you mob
Cheers
have you got the thermostat round the right way ?
Yep. Double checked that and all the other hose routing...
FWIW:
My last two coolant issues:
1/. my dads little Peugeot 307 Hdi. electric fan struggles to come on, on what I think should be a low speed, and only comes on if A/C is tuned on, or it eventually reaches 100°C on the gauge. Radiator is never too hot to touch. Not cool, just never as hot as supposedly 100°C coolant should be!
2/. my own D2 V8 project car. came to me with a history of overheating, so went about sorting coolant anomalies created by other mechanics. I had it idling in my driveway for 1-1.5hrs after I'd done some work, never overheated, but on a short drive overheated. Radiator never too hot to touch too. A few weeks ago pulled rad, found it blocked up to high heaven(maybe 1-2% flow) with some sealing additive. Changed rad let it idle for another 1 hr, coolant registered 90°C and then dropped to 88°C took it for drive coolant registered 85°C on this short round the block drive.
Assumed it's overheating issue was almost completely sorted, gave it one more flush, before I did that tho, once again radiator was never too hot to touch .. I'd say 'luke warm' or ambient temp .. after the drive around the block.
Only two cars I've personally ever had anything to do with that have had this same strange happening.
I know my D1 at normal operating temp heats the (copper) rad what you'd expect to be normally. Going to check brothers Td5 one day to see too.
.. weird stuff.
Arthur.
'99 D1 300Tdi Auto
'03 D2 Td5 Auto
Have you got a good stream of coolant coming out the telltale/ bleeder, and the heater blowing hot air?
Yes heater hot, blip the accelerator and coolant shoots out of bleeder. Coolant is circulating back into expansion tank...
Mmmm interesting. This radiator is completely cool though. And yet not overheating. Although that is just based on the coolant temperature taken from the top rad hose which may not be circulating so could be painting an incorrect picture. It doesn't smell like it's overheating though either...
I find a Infra- red thermometer is a handy tool to have in the kit, if you are still using the original hose clips on a leaky joint you could try a worm drive clip to see what happens.
These Td5 cooling systems will make your old very early with worry, i still have a small amount of gurgling in the heater it goes away after a minute so “it is what it is “.
what temp thermostat you got?
have you felt the bottom hose out of the rad?
also feel the by pass hose to the thermostat as until the radiator is at engine temp that is where most of the coolant will travel through with a little bit out of the radiator to the control of thermostat temp.
thermostat in the bottom hose don't really get the radiator hot unless the full cooling capacity is required.
for coolant loss have you got any weeps?
have taken the expansion tank and raised it well above the engine to get rid of any air? best to do this with the engine at temp the radiator blocked off so the thermostat is open to encourage air to escape, even better if you have ramps to drive up on to encourage any air to the front of the engine
Thanks all for the replies. Tonight I replaced a couple of the old clips, tightened up a few more. Bled it again, this time with the engine running and I am getting some heat into the radiator. Hallelujah! Also the bottom hose is heating up which it wasn't before. I can't take it for a test drive until tomorrow as I've had too many beers this evening. Fingers bloody crossed. Will update tomorrow.
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