Overheating 300TDI

Ziva · Sep 13, 2023

Hi All,

The mystery continue. The car came back and it is not overheating while standing still. I ran the engine for one hour and nothing. However, water comes back in the expansion tank and overflow. This empty the cooling system.

i also noticed the heating is not producing hot air.

tonight We did the followings:
change The water pump. Did not look bad
change the thermostat. Did not look bad
run water from the top to the bottom of the radiator. water runs freely.
still not mayonnaise in the oil.

i am running out of idea. I cannot figure out why the water is not circulating.

do you have a idea?

thanks.

Ziva · Sep 13, 2023

Hi All,

The mystery continue. The car came back and it is not overheating while standing still

kevstar · Sep 13, 2023

Came back from where a proper garage, whats the compression test results, sniff test done, pressure test done.

Bypass the heater matrix & bleed properly as per the manual. Running a hose through a rad doesnt make it a good unit.
Checked a thermostat by looking at it,

Reminds me when I sent a lad for a thermostat for an old vw bettle

tottot · Sep 14, 2023

If coolant being blown out of pressure tank and overheating starts shortly after then you have a head gasket issue. Likely cylinder's two or three leaking combustion gas to the coolant ways. Head off time.

D1Nut · Sep 14, 2023

a cheap thing to do is a new expansion tank cap

Ziva · Sep 14, 2023

D1Nut said:
a cheap thing to do is a new expansion tank cap

Thanks, forgot to mention but it is done.

What I really do not understand is why it overflow directly and it looks to me like not circulation rather then exhaust gaz. I have no weird oil and no white smoke.

D1Nut · Sep 14, 2023

The heater not working is possibly a clue

Are the pipes coming and going to the head and firewall very hot to touch - cause they should be

Is top radiator hose getting very hot - cause it should be

tottot · Sep 14, 2023

Ziva said:
What I really do not understand is why it overflow directly and it looks to me like not circulation rather then exhaust gaz. I have no weird oil and no white smoke.

If all that is happening is gasses going from a cylinder into the coolant ways there will be no weird oil and no white smoke.
Just coolant being blown out of the system, result because heater unit is high it runs out of coolant first, hence no heat.
The 300tdi has a high on the block coolant pump and soon runs dry as coolant is blown out, hence no circulation.
No good will come of delaying any more. Head off time.
I have seen a 300 that lost coolant and then ran so hot that number one piston became a melted lump of metal.

lynall · Sep 14, 2023

I would go with head gasket, and whilst head is off get it pressure tested.

D1Nut · Sep 15, 2023

I have seen our brit in canada using an all metal head gasket and he likes them = a lot

Ziva · Sep 18, 2023

Dear All,

last weekend I did the checks that you all proposed:
- checked the oil : not missing and no strange colour (not diluted nor oil)
- changed the water pump (the old one was fine)
- changed the thermostat (I still need to test the old one)
- changed the expansion tank cap
- bypassed the heating element.

I bleded the air out of the cooling circuit the best as I could and went for a test drive, the engine now only overheat (based on the needle) when going up hill (slight incline) or when keeping a high rev. the needle stay at about 1mm from the red zone, as soon as I stop then needle goes down. and I am not loosing coolant anymore through the expansion tank nozzle.

I still very worried and I do not know what to do next except changing the head gasket.

I am heading more towards the radiator?

D1Nut · Sep 18, 2023

So that heater bypass might be a key - they are a known weak point and leak

If it is indeed the heater leaking i am surprised you didn't pick up the smell of anti freeze in the cabin and the drivers side carpet should be wet on the left top

If the heater matrix leaks it allows pressure to escape and drops the boiling point of the water

On the bleeding process this is my very long winded way of doing it

Cap tight on the expansion bottle
unscrew big bolt from top of thermostat housing
unscrew same bolt from top of radiator
keep filling the thermostat housing slowly till no more bubble's coming out of top of radiator - while it's still over flowing at top of radiator screw bolt back in and tighten
screw bolt back into top of thermostat housing till finger tight
open expansion bottle cap and level needs to be at max 1 inch above the seam of the tank

when done tighten it all up - this should be done with a stone dead cold engine

Your bolt's on the thermo and radiator might still be the plastic ones and I have put the brass ones in years ago

that needle near the red isn't a nice thing at all but let's see if it helps

lynall · Sep 18, 2023

Ziva said:
Dear All,

last weekend I did the checks that you all proposed:
- checked the oil : not missing and no strange colour (not diluted nor oil)
- changed the water pump (the old one was fine)
- changed the thermostat (I still need to test the old one)
- changed the expansion tank cap
- bypassed the heating element.

I bleded the air out of the cooling circuit the best as I could and went for a test drive, the engine now only overheat (based on the needle) when going up hill (slight incline) or when keeping a high rev. the needle stay at about 1mm from the red zone, as soon as I stop then needle goes down. and I am not loosing coolant anymore through the expansion tank nozzle.

I still very worried and I do not know what to do next except changing the head gasket.

I am heading more towards the radiator?

How hard/solid was the top rad hose after the roadtest?

Ziva · Sep 20, 2023

lynall said:
How hard/solid was the top rad hose after the roadtest?

Quite hard and soft before the start

Dr Strangeglove · Sep 20, 2023

Have you looked at your radiator to check it's OK. They often look fine at the front but when you touch the fins at the rear they turn to dust.

On both my RRCand my defender they were both like this. When taken out and you poked the fins between the tubes, the fins just turn to dust in a pile on the floor. I would say on mine only 20% of the fins were any good - that's a lot of heat transfer you are loosing!!

Ziva · Sep 20, 2023

Dr Strangeglove said:
Have you looked at your radiator to check it's OK. They often look fine at the front but when you touch the fins at the rear they turn to dust.

On both my RRCand my defender they were both like this. When taken out and you poked the fins between the tubes, the fins test turn to dust in a pile on the floor. I would say on mine only 20% of the fins were any good - that's a lot of heat transfer you are loosing!!

indeed, this is what I am ordering at the moment. however, I wanted a bigger radiator as I am towing a lot but I could not find any. same for the hoses, I will change all of them.

Dr Strangeglove · Sep 20, 2023

Ziva said:
indeed, this is what I am ordering at the moment. however, I wanted a bigger radiator as I am towing a lot but I could not find any. same for the hoses, I will change all of them.

I hope its a fix for you but also consider the low coolant alarm as it gives peace of mind. Have a look at the condition of your hoses too as you don't want to get the radiator off and not be able to refit it due to a perished hose or broken hose clip.

Dodgy Den · Sep 20, 2023

Is there any fluid leaking out of the radiator expansion tank where the 'radiator cap' is? I had a TD5 Defender that was like your is. I changed the cap and it still leaked fluid so i then went for a head gasket. I had no emulsification at all just pressure in the header tank and leakage of the orange coolant. When i took off the head you can see in the picture that i had a holed head due to someone not using the right coolant and just using water!!!!!! On an alloy head you must use 'OAT' coolant which is orange or the water rots the alloy like on mine. Cost was £1300 for a new head plus fitting costs.....so be warned!!!

v8250 · Sep 20, 2023

I'll just leave this here

Ziva · Sep 20, 2023

Dodgy Den said:
Is there any fluid leaking out of the radiator expansion tank where the 'radiator cap' is? I had a TD5 Defender that was like your is. I changed the cap and it still leaked fluid so i then went for a head gasket. I had no emulsification at all just pressure in the header tank and leakage of the orange coolant. When i took off the head you can see in the picture that i had a holed head due to someone not using the right coolant and just using water!!!!!! On an alloy head you must use 'OAT' coolant which is orange or the water rots the alloy like on mine. Cost was £1300 for a new head plus fitting costs.....so be warned!!!

very interesting but you scare me because I always refilled the tank with water in recent weeks (since the problem arises to test the system) I have personally never used the orange coolant but always the one I find at the petrol station.

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