Coolant leak on 2.0 bluehdi - is this serious?

[sneakyfox]

I have a coolant leak on my Boxer and am wondering if it's something I need to take a look at or if it's okay to just top up with coolant when it drops down.

It leaks around 120-150ml per month.

It can't quite get to see exactly where it leaks out but these are the best photos I could get.

The pipe marked with X in both pictures is the same. The second picture is taken from below.

The coolant runs down above the pipe and then runs on to it. I'm not sure the colour is really from rust, but rather from dirt on the outside of the engine.

Appreciate any thoughts!

[mickthemaverick]

There are mixed views on slight coolant leaks. Some say try using a sealant like radweld and others say don't let it near your engine. I would try checking all the hose clips for security and then possibly try a pressure test with the engine off and see if you can spot the weep.

[myglaren]

I certainly wouldn't let Radweld or Barr's Stop Leak anywhere near anything that I owned but Forté Radiator Stop Leak & Cooling System Conditioner is recommended for Citroens and indeed essential for the warranty if fitting a Valeo heater matrix. IIRC I believe that Liquimolly have a similar product.
https://www.forteuk.co.uk/product/radia ... nditioner/

[windy1603]

I would not leave it for long as air can get trapped in the head and cause the head to overheat, boiling the coolant which then vents from the header tank.

You may be lucky and its just the gasket on the thermostat housing if not a new housing will be need. Based on my experience not the easiest to change (the clamp bolt on the solid pipe that goes behind the engine is a pain) and they are very expensive I was quoted over £300 from Peugeot got a quality OEM replacement (had the PSA Logo's ground off) for £145

[sneakyfox]

Thank you for the replies!

I seems like Forte is not a thing here in Spain but there is this Liquid Moly product: https://www.amazon.es/Liqui-Moly-2533-R ... B01DT5TZ8A
It looks like Wynn's has a similar product too.

I don't think I have the tools to do a pressure test, I guess you need a compressor and fittings for that? So it would probably be a trip to the mechanic in that case.

I would not leave it for long as air can get trapped in the head and cause the head to overheat, boiling the coolant which then vents from the header tank.

You may be lucky and its just the gasket on the thermostat housing if not a new housing will be need. Based on my experience not the easiest to change (the clamp bolt on the solid pipe that goes behind the engine is a pain) and they are very expensive I was quoted over £300 from Peugeot got a quality OEM replacement (had the PSA Logo's ground off) for £145

Sounds like it's going to be some work.

For what it's worth, after heating up the needle on the temperature gauge sits right in the middle, never moves at all.

I have never seen any liquid or smudge around the header tank. Even if coolant escapes as steam wouldn't it still leave traces there?

It looks like you can get a new aftermarket thermostat for 110€ in Germany: https://www.autodoc.de/fast/22054447
There are more expensive ones too.

[PaulC5]

The hose clip on the lower photo looks to be missing the screw part that tightens it up if it is a jubilee clip. If so it might just need a clip replacement.

[sneakyfox]

Thanks but I think there is a screw on the opposite side, not visible on the photo. But the coolant is running down from above, probably somewhere on the thermostat housing.

[sneakyfox]

Went to the mechanic and they confirmed that the thermostat is leaking. They then tested the coolant for gas leaks and confirmed that the cylinders are leaking a bit. The chemical was slowly changing colour to green.

So that's why the thermostat is leaking.

Obviously changing head gasket and seals was not what I was hoping for. Now considering whether to do something about it or not. It's only a small leak after all. They said the pressure leak is unlikely to get worse, but possibly the thermostat will die at some point.

[Rp0thejester]

So basically change the thermostat and everything is okay?

[Stickyfinger]

No Stop-Leak product will stop a pressure leak from the cylinders.....however, I am very surprised that the pressure in the cooling system is not increasing more than it is. Blow-by is not often "leaking a little".

IF it is the case that you have blow-by then it needs doing now. Finding that it needs a new head gasket the way you have and at the time you have allows for a very easy gasket replacement without a head rebuild and other costs generated by a more "violent" event with follow-on damage/contamination.

I would fall on the ... Fix the thermostat leak, refill with clean coolant and Re-Check the head leaking test with a clean/new test kit. If it needs doing OK, if not you waste nothing (even recover the new coolant for re-use)

Went to the mechanic and they confirmed that the thermostat is leaking. They then tested the coolant for gas leaks and confirmed that the cylinders are leaking a bit. The chemical was slowly changing colour to green.

So that's why the thermostat is leaking.

Obviously changing head gasket and seals was not what I was hoping for. Now considering whether to do something about it or not. It's only a small leak after all. They said the pressure leak is unlikely to get worse, but possibly the thermostat will die at some point.

[sneakyfox]

So basically change the thermostat and everything is okay?

No they say that a new thermostat will likely start to leak as well because the pressure leak from the head is still there to blow it open.

No Stop-Leak product will stop a pressure leak from the cylinders.....however, I am very surprised that the pressure in the cooling system is not increasing more than it is. Blow-by is not often "leaking a little".

IF it is the case that you have blow-by then it needs doing now. Finding that it needs a new head gasket the way you have and at the time you have allows for a very easy gasket replacement without a head rebuild and other costs generated by a more "violent" event with follow-on damage/contamination.

I would fall on the ... Fix the thermostat leak, refill with clean coolant and Re-Check the head leaking test with a clean/new test kit. If it needs doing OK, if not you waste nothing (even recover the new coolant for re-use)

Okay, thanks for the idea! What are your thoughts behind doing a new test? Why might that give a different result?
Are you thinking that exhaust gas might enter into the coolant from outside through the leaky thermostat?