Engine coolant connector problem.

[Captain Beaky]

Hello Folks.

BMC 1800.

Last weekend one of the connectors in the engine-to-calorifier circuit came apart resulting in a few litres of antifreeze to mop up in the bilge. Sorry no pictures at the mo. There is an initial hose from the engine and then jointed to hard pvc plastic plumbing.

The connectors are plastic compression type, about 15mm, an outer screw-on ring connecting with an inner threaded pipe with the compression part and O ring. Checking out pictures on here seems these are used quite a lot on the circuit to the heating coil in the calorifier. When it parted the outer ring and O ring remained on the loose pipe, that is the screw thread appeared to have come undone.

So my question is ( at last ) is, if the pipe had blown out I would expect the pipe section alone to blow out, leaving the screwed cap done up tight and still in place. Can anyone tell me if excess pressure could be the cause of a screw thread undoing, or is it maybe just a badly done-up connector being vibrated loose? The connector is just positioned in contact with the engine bulkhead, at the end of the hose from the engine, top connection.

Any thoughts please?

Thank you !

 

[David Mack]

Photo would help!

If the nut, lock ring and o ring are all still in place on the pipe and the threaded part of the fitting is undamaged I would say it must have vibrated undone, unlikely as this sounds. I would just reassemble, make sure the nut is done up as tight as you can get it, and cautiously try the engine again. You will need to top up the coolant and check for any air locks which may have developed as a result of the partial drain down.

[Tracy D'arth]

The description sounds like an Acorn/Hep2o fitting. Should have a cap nut, stainless grab ring, and "o" ring still on the pipe end with a stainless insert sleeve inside.

If so just screw it up again.

Providing the insert is inside you will not pull or blow the pipe out, they will withstand at least 10 bar pressure, the pipe will burst first before the fittings let go.

[Captain Beaky]

Thanks both for helpful comments.

Yes I did top up, ran the engine without pressure cap for 10 minutes, then cap on, up to temperature again. All ok.

I'm hoping to go back this weekend, and will take a photo or two. I will also check there are no steel ( or plastic ? ) compression parts left on the bilge floor !

Cheers Mike

 

[Captain Beaky]

Hi again. To complete the story here's a pic of the connector that undid. On closer inspection a bulkhead pipe clip has snapped, allowing the elbow movement  to rub against the bulkhead. The paint behind it is rubbed clean. Funny how when it rubs it only manages to loosen and not tighten! By the way they are branded Hepworth.

 Cheers

 

[Tracy D'arth]

On 11/08/2021 at 19:11, Captain Beaky said:

Hi again. To complete the story here's a pic of the connector that undid. On closer inspection a bulkhead pipe clip has snapped, allowing the elbow movement  to rub against the bulkhead. The paint behind it is rubbed clean. Funny how when it rubs it only manages to loosen and not tighten! By the way they are branded Hepworth.

 Cheers

 

Brilliant! The vagaries of plumbing!

The clip needs to be closer to the fitting to prevent the rubber hose  pressing the cap nut onto the bulkhead.  Rare for these to unscrew if done up tight. Hep2O stuff is very good, used miles of it and thousands of fittings and had no problems with it.

[Scholar Gypsy]

This reminds me how I once drilled a hole in a bulkhead, and the drill bit just managed to unscrew one of these fittings that was hidden behind, on the main water circuit. Cue the water pump starting and a bit of water in the cabin bilges.  The joint was completely inaccessible so I had to cut a section out and add a trombone shaped piece of plumbing to join it all up again....