D2-55: Cooler lid - unknown modified connection to coolant reservoir

[Krumelur]

Can someone maybe help explain how/why/if my D2-55 was modified to have the coolant reservoir connected to the lid of the heat exchanger?
Please see the image attached. I have various questions:

1. Shouldn't there be some hose connected to this outlet? Where should it be connected to?
2. What should be connected to this closed port?
3. I cannot find this lid anywhere in the spare part catalog. It's leaking and I wanted to replace it. I am able to twist it about 30 degrees but cannot take it off. Something seems to be attached to it on the inside and that thing doesn't wan to come off/out.

My goal is to renew the lid which has really seen better days or to get the whole thing back into its original state.

[JEN-et-ROSS]

Hi...
 No 1.. I reckon this would normally be the overflow or the connection to an expansion tank if one is fitted..
 No 2.. Could it be a calorifier connection...?? otherwise I've no idea..
 No 3.. You would usually find a bog standard radiator pressure cap here, probably about 10-15 psi...

Interestingly, if an expansion tank is fitted the pressure release (radiator) cap would normally be on that instead of the heat exchanger, but the black cap on your expansion tank doesn't look like normal radiator type cap...
As to why this was installed...?? ,I'm as flummoxed as you are..........Bill

[Krumelur]

I found it. At least, there is an official spare part at https://www.bootsmotoren.de/Volvo-Penta--Online-Ersatzteilkatalog-7744440-26-48.html

Part #9 is "only" €150 - hahaha

[JEN-et-ROSS]

Good grief...!! What is it all supposed to do..??...
It's the most complex (and therefore potentially troublesome) system I've ever seen.............

[symphony2]

I believe it is fitted to raise the expansion tank and when the calorifier is mounted higher than the engine

[JEN-et-ROSS]

I found it. At least, there is an official spare part at https://www.bootsmotoren.de/Volvo-Penta--Online-Ersatzteilkatalog-7744440-26-48.html
Part #9 is "only" €150 - hahaha

I've just looked at the website.... The prices VP charge are eyewatering...!!

[sean c]

Krumelur,
I had leakage around the lid on my D2 75F. I had trouble getting the lid off also. There wasn't anything stopping it except the lid locking mechanism had bent a bit. I ended up bending the locking parts out with a pliers, removing the lid and then bending it all back in place so it locked correctly.
There is no spring to maintain pressure and it seems to rely on the rubber seal, part #10. I bought a new seal and compared to the one that came out it was significantly thicker. The old seal had compressed and was not sealing.
The cooling system is designed to run at 0.09MPA according to the workshop manual, page 71.
The new seal fixed my leakage problem.
I have uploaded this workshop manual to the relevant section on this site as I did not see it here.
I can't recall how much I paid for the seal but it was not expensive.
On the fitting #2 on you diagram I have a hose running down to the engine bilge so that overflows don't run over the engine. I have the hose sitting in a small drink bottle so that I can easily see if there is any discharge.
regards,
Sean

[sean c]

See attached photo of old vs new sealing ring.
#2 is not the calorifier. Mine is blanked also and my calorifier is working fine.
Sean

[Yngmar]

Good grief...!! What is it all supposed to do..??...

Keeps your heat exchanger topped up with coolant, accepting overflow when it expands (warming) and returning it when contracting (cooling). Also a level monitor that alerts you when your coolant has dropped too low, so you don't have to monitor it as part of your regular engine checks.

Standard stuff every car has had since the last decade or two.

[robmeer]

Usually this expansion tank is installed later on, when a water heater (boiler) has been added, thus increasing the volume of coolant in the system. The nr 1 pipe was the original 'overflow' for the system when no expansion tank is fitted.

[Krumelur]

I ordered all kinds of seals from parts4engines. I got the lid seal ring and a heat exchanger gasket and seal kit for around €22.

Thanks for advice on "bending" the lid. I'll give that a try.

[PEA-JAY]

Reference the D2-55 expansion tank option, I have a D2-55C  It didn't come with the expansion tank notwithstanding high summer temperatures (Med) and no added ventilation in the engine compartment. To monitor any coolant loss I extended the plastic pipe beneath the pressure cap to loosely terminate into a small plastic bottle. This collects any coolant lost during use. Seasonally I find perhaps 3cc coolant in the bottle. (The boat is fitter with the standard calorifier)

[IslandAlchemy]

All you need is a new sealing ring for inside the cap. You can get them from a VP dealer for about 5 Euros.

[Krumelur]

Yep, got that too.