Leaking heat exchanger Volvo 2030

[Int14]

Sea water is getting into the fresh water circuit, causing the filler cap to vent and lots of coolent in the bilge. The cause is the domed rubber cap, which connects the sea water cooling hose to the heat exchanger, is failing to seal, on the smaller diameter part that seals on the sea water cooling tube. The jubilee clip is failing to do its job, as there is not enough of the heat exchanger to tighten up against. The clip then twists off as it is tightened. I think the jubilee clip is also tending to slacken as the engine runs.

As this is such a common engine, I assume there is a solution to this. The high torque jubilee type clips are wider, which makes then unusable. Is there a better clip which is narrower than a standard jubilee for a 70mm diameter application?

Is there a sealant or other solution to "lock" the jubilee clip onto the rubber cap so it won't slip off?
Any other ways of solving the problem?

many thanks

 

[Martin_J]

Are you sure the heat exchanger tube stack is located with equal parts showing at each end. Just wondering if with too little out at the problem end there is perhaps too much sticking out at the other end.

I never (touch wood) had any issues with enough width to clamp using standard clips.

 

[Cantata]

Just to reinforce Martin_J's point - I had exactly this problem on a 2020, where I had removed the cooling stack to clean it out, and when I replaced it I failed to ensure there was an equal amount poking out each end of the chamber. I was plagued with seawater getting into the system until I twigged what I'd done wrong.

 

[vyv_cox]

As I'm sure you know, what you are experiencing is theoretically impossible. The coolant pressure is controlled by the pressure cap to a figure well above atmospheric, 12 psi being a common value. The seawater system is open ended, so at atmospheric pressure or a little above maybe to allow for system resistance. If seawater is getting into the coolant its pressure is exceeding the cap pressure. Several owners have experienced the same problem and in the majority of cases it is because the exhaust manifold is caked with salts, back pressuring the seawater system. Cleaning this up will almost certainly solve the problem.

There is a second possible cause that I wrote up in a PBO article last year. If a calorifier tube has a leak then fresh water at about 28 psi can enter the coolant circuit, causing the symptoms you have observed. However, if coolant does not leak when the engine is not running then this cannot be the cause.

 

[Cantata]

Should have added to my post, as per Vyv's comment, that after each engine run I found coolant in the bilge beneath the engine that had arrived there via the pressure cap overflow pipe. That was the initial mystery - coolant under the engine, yet coolant level in the engine exactly correct. I fixed it as discussed eventually (and ensuring there was no sea water left anywhere in the system is another story) but the following winter I also replaced the exhaust elbow which was badly corroded, and had probably pushed up the seawater pressure in the system.