D2 55 heat exchanger cap leak

[elias]

Hi to all,
I noticed a leak around the neck of the heat exchanger cap as seen in the pic . Does anybody knows if it is separate piece and just screws there or welded ? Any other experience on this issue ?

[IslandAlchemy]

If you are talking about at the bottom of the neck where it joins the coolant tank, it is welded.

Apply a fillet of JB Weld if it's leaking.

[elias]

Τhanks for the advice . You mean externally ?

[elias]

I have the suspicion that is the cap causing the leak , I just fill till the top and wait to see if it leaks in one two days

[PEA-JAY]

You seem to be overfilling the system!
There is a high level mark in side the header tank and only fill to that level when the engine is cold.
Probably it won’t leak if you do so

[Markus]

Hi to all,
I noticed a leak around the neck of the heat exchanger cap as seen in the pic . Does anybody knows if it is separate piece and just screws there or welded ? Any other experience on this issue ?

Seems to be similar design to my MD22 which had also a tiny leak. The leak was in the brazing/jointing between neck and the heat exchanger. I cleaned the area as best as I could and used Loctite 7649 primer and Loctite 290 on it. The latter is a thread lock compound which is used after assembling bolts and penetrates the threads by capillary action. My reasoning was that this method should seal the whole leak path as opposed to just an external patch with jb weld or similar.

[elias]

So last night I fill to top as seen in pic and then in morning I found that leaking stopped to the level of pic 2. You can see that there are 2 tiny cracks at that level , any ideas for material to use to cure it ? Be aware that must be very thin so the gasket of the cap seals evenly

[IslandAlchemy]

You should only fill up to about 25mm from the top of the tank, not right to the top.

[elias]

It has also en expansion tank connected with a T shaped cap like the photo

[MagicalArmchair]

Hello, Mine has the same set up, and mine was leaking too and I couldn't identify from where!

I found the below from Tino, and replaced the rubber bit he has replaced and I hope that works. The thinking being it is releasing too early, at too low a pressure and venting coolant.

https://www.youtube.com/watch?v=9jsslJTx9yw

[IslandAlchemy]

It has also en expansion tank connected with a T shaped cap like the photo

Ah!

If you have an expansion tank, you will have a rubber seal inside the tank cap.  These can leak (mine did).  They are about £5 from a VP dealer.  Get a new one.

Part number 1543751 - as shown in the video posted by Magic Armchair above.

[elias]

Thank you so much guys , I ordered the cap rubber gasket , I ll inform when I have it checked

[Jake]

I have been meaning to replace the gasket too.  My cap is slightly loose and I see a small bit of coolant around the cap from time to time.  It has been pretty low on my work list, but is certainly easy to do.

Jake

[elias]

UPDATE . Change the gasket , still leaking . I ll try to solder it with a chemical compound as Markus proposed and I ll inform about the result .

[elias]

UPDATE 2.
Cold weld with Permatex epoxy .
 1.with a big syringe I took out some coolant until the level is some centimetres lower from the leaking point .
2.Paint remover around the neck , grinding to make a clean and paint free surface.
3. Heat it with a good lighter around the hair cracks to get rid of the moisture inside .
4. Mix and apply the weld
5. Remember to put the seal like the Volvo parts diagram

Day one but without engine running no leaks so far .

[Yngmar]

It'll be interesting if that holds up to the thermal stresses of a few hot/cold cycles (engine running a few hours, then cooling down, etc).

It looks like a brass fitting in an aluminium heat exchanger, so different thermal expansion might be why it developed a leak in the first place.

Personally I would've tried something more flexible, like a high temperature silicone sealant. If the epoxy cracks, perhaps give that a try.

[elias]

That’s correct , I ll inform . But do you suggest a particular sealant so I can have it already on board ?

[Yngmar]

High temperature silicone sealant, whatever you can find where you are. The one I used when rebuilding the Volvo exhaust muffler happened to be red and rated to 460°C or so, but it doesn't even need to be that high. The heat exchanger cap shouldn't get much hotter than the coolant, so anything with at least 100°C long-term rating (check sealant data sheet - product listings often only feature peak rating) ought to be fine.

[elias]

Update
After 25hours , no leaks . Used the epoxy weld