300tdi loosing coolant

Hi I’ve been scratching my head on this one for a while.. Please do help if you can.
I have 1995 tdi 300 110 done about 130k miles and it seems to lose coolant at about the rate of 1.25 litres every 500 miles or so... I replaced the header tank with a clear one... replaced pressure cap... replaced heater hoses.... checked for exhaust gasses in water (not present).. inspected as best I can p gasket nothing really evident?? I have replace y shaped bleeder hoses to header tank.... it’s a slow leak which occurs mostly on long runs... no overheating and heater works.... Any ideas? Thanks for looking any advice welcome as I’m a novice

Ohh I don’t think it’s the heater matrix as no water in passenger footwell.... I think it’s leaking and evaporating as the are no drips I can see or visible stains? Perhaps the p gaskets gone but no obvious marks...

Have a look at the area below the heater box under the bonnet.

tottot said:

Have a look at the area below the heater box under the bonnet.

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Hmm rusty but no stains or drips I’ll keep an eye on it though cheers.... I think I’ll get the system pressure tested next ?? I took it to the garage and they said don’t worry to much but keep an eye on it?

William Marshall said:

Ohh I don’t think it’s the heater matrix as no water in passenger footwell.... I think it’s leaking and evaporating as the are no drips I can see or visible stains? Perhaps the p gaskets gone but no obvious marks...

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Assuming you are using antifreeze in your coolant then an iffy player gasket is easy to spot

Marmaduke said:

Assuming you are using antifreeze in your coolant then an iffy player gasket is easy to spot View attachment 147462

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Ohh that’s dramatic is it as easy to see when assembled? I’ll have to poke around with a torch although I didn’t notice the rust last time I looked I do have the gaskets in the workshop in case they were needed? The garage mechanic also looked there and didn’t think it was the p gasket... Thanks for the photo and advice I’ll look again

William Marshall said:

Ohh that’s dramatic is it as easy to see when assembled? I’ll have to poke around with a torch although I didn’t notice the rust last time I looked I do have the gaskets in the workshop in case they were needed? The garage mechanic also looked there and didn’t think it was the p gasket... Thanks for the photo and advice I’ll look again

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Ohh and yes antifreeze is in the coolant thanks

It occurs to me it is possible it’s in the radiator area? I don’t fully understand the water flow in the engine but sort of assuming that when it’s hot the thermostat opens putting coolant circulation to the rad and when it’s not it doesn’t? So perhaps on long runs it opens the leaks somewhere there? The radiator looks ok but I’m not sure what to look for there

I had a really annoying leak I couldn’t find for ages. In the end I got a UV dye I put in the coolant and that showed it up and a couple of others aswell.

It stays forever in the engine though but it worked for me

flat said:

I had a really annoying leak I couldn’t find for ages. In the end I got a UV dye I put in the coolant and that showed it up and a couple of others aswell.

It stays forever in the engine though but it worked for me

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Ohh that’s an interesting idea I’ll look into it

William Marshall said:

Ohh that’s an interesting idea I’ll look into it

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Out of interest where were the leaks?

I’ve just ordered some so we will see. Thanks for the tip

After having my local garage refit the p-gasket for a second time as it was still leaking I was told that the bolts holding the water pump on could do with being longer.
I'm not convinced they used the correct seal actually.

gymmaniac said:

After having my local garage refit the p-gasket for a second time as it was still leaking I was told that the bolts holding the water pump on could do with being longer.
I'm not convinced they used the correct seal actually.

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housing could be warped or surface pitted, the correct bolts are long enough

jamesmartin said:

housing could be warped or surface pitted, the correct bolts are long enough

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agreed. so far it hasn't leaked again though.

William Marshall said:

Out of interest where were the leaks?

I’ve just ordered some so we will see. Thanks for the tip

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Mine is a 200tdi but it was fron around one of the water pump bolts and the rad was weeping - it was never wet though so I think it was evaporating, but it left a uv dye stain behind.

Also showed up that a couple of hoses weren’t nipped up right

Ok I’ve ordered the uv stain I’ll report back thanks for all your help Will

Don't you need a UV lamp as well?

Flossie said:

Don't you need a UV lamp as well?

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Just wait for an 80's night at your local discotheque

Stick some K seal in it !

Flossie said:

Don't you need a UV lamp as well?

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It comes with that all for a tenner