300tdi Coolant Leaking Out Of Cap

Just as you sort one problem... Another 3 come along.

Noticed this last week that if I use the disco for a run where the engine has a chance to sustain running temperature for a while, when stopped on the drive or road, etc a little coolant appears on the floor!

Upon opening the bonnet you see a little bit of coolant leaking from the header tank cap

Now the gauge doesn't show that it is overheating, it sits about half as it always does when running warm. No leaky hoses or anything. No engine light has come on.

It had a cambelt just over a month ago and they obviously changed the coolant when refitting the rad.... Could it be that they overfilled slightly?

Airlock? Broken cap? Broken disco?

Any ideas???

What is the fill level on a 300tdi in the header tank. I can't see no marks.

matthew2riches said:

Just as you sort one problem... Another 3 come along.

Noticed this last week that if I use the disco for a run where the engine has a chance to sustain running temperature for a while, when stopped on the drive or road, etc a little coolant appears on the floor!

Upon opening the bonnet you see a little bit of coolant leaking from the header tank cap

Now the gauge doesn't show that it is overheating, it sits about half as it always does when running warm. No leaky hoses or anything. No engine light has come on.

It had a cambelt just over a month ago and they obviously changed the coolant when refitting the rad.... Could it be that they overfilled slightly?

Airlock? Broken cap? Broken disco?

Any ideas???

What is the fill level on a 300tdi in the header tank. I can't see no marks.

Click to expand...

Airlock? Broken cap? Broken disco? maybe

What is the fill level on a 300tdi in the header tank. I can't see no marks should be half filled where the tank is joined

I'll get me hammer out in the morning and have a look.

I'm guessing it has been slightly overfilled if it is up to the seam. I recall it being slightly higher. And with the hotter weather just lately, the water might be slightly hotter causing more expansion.

I've just been out there in the dark, back from work and there isn't any coolant on the floor!!!

I reckon it was overfilled when it had its belts done! We'll see if it starts leaking again on Wednesday as I should be off to Kent to grab a surprise.

Get some brass replacement bungs and bleed any air off from the top of the thermostat housing.The fill level is,as said,the seam,or covering the top of the post inside.If you are getting an overheat,get it sorted now before the head goes on you.Have a look at the inner surface of the radiator,maybe brush it GENTLY with a soft big paintbrush if there is crap on there.I have learned the hard way about low water in 300s.We had a thread before about a low water warning mod,someone found a nice handy device to fit the header tank.I am toying with the idea of incorporating the sensor-cap from a peugot XUD engines header that I have around.

It's not overheating, this is the thing that confused me. Temp gauge is sitting as it should.

Good point about the rad. It's been through water and mud over the bonnet so I might give it a dust. A gentle blow with the compressor and vacuum might help too.

I saw the X post inside the coolant bottle today. It is sitting on that so it is right now???

No more water has dropped out this morning.

We're doing a weekend offroading at Rougham airfield this weekend so we'll see if there is any issues. If it blows up, it blows up I'll keep an eye on it but I think it was just overfilled.

Just to bring this back up..... it's still doing it. Noticed it today again. Hasn't done it since last post.

What is going on lol?

Have you replaced the cap?

arienol said:

Have you replaced the cap?

Click to expand...

There are alot of quite simple things that may be causing this.

Airlock - as said before check this out first as it is quite likely. Take out the bung in the top hose and mahe sure you get clear water comming out.

Over fill - what is the cold level like - was it overfilled when you got the cam belt done

Knackered filler cap - quite possible that the working pressure isn'y being acieved as the cap has failed. - No real way of checking - just stick a new one on a try it.

Blockage in coolant system - radiator likely, thermostat likely, heater matrix very likely.


It starts to go downhill a bit from here.....

Head gasket - Get it checked as it could be exhausting into your coolant system. This happened to me on a TD5 and it was actually more of an explosion of coolant onto the floor rather than a slow prolonged problem - but it depends on how the car is being used etc I suppose.

It's worth considering replacing the hosing and one way valve that goes between the expansion tank and head, only £20 or so and I'm almost convinced that this little b*****d not letting water back into the head was a least partly to blame for our recent head failure

Aye,that a one way bugger,that little valve....much overlooked