Talk Morgan Forums Morgan Sports Cars Morgan Plus Four, Supersport & Plus Six (CX & CXV Generation Vehicles) Radiator cap failure

Over the last few months, I've had a steady drop in the passenger side (engine) coolant level - I'd been getting leakage from the overflow at the radiator cap. The system wasn't overfilled and I suspected the cap was failing, so I ordered a new one (Motorad lever type, 16psi)

Went out today to change the cap and the old cap fell apart as I took it off!

Car is just over 3 years old. I may change the other cap too...

(ugh)

Jim, You learned a lesson we all must. There is nothing more important to a pressurized cooling system than the pressure cap. How many of us keep a constant eye on the cooling gauge..or the oil pressure gauge for that matter?! Please understand that I am a long distance mogger. Everything happens to those whose normal single mogging trip is 3000-7000 miles. We cannot afford a breakdown 1000s of miles from home. I carry some parts in bins I have made in the rear axle cover. A coolant blanking cap and a pressure cap is among them

1. Check your coolant level and your pressure cap and blocking cap regularly. Carry spares, a safety cap. (below) A safety cap costs no more and and eliminates the loosening that vibration can cause. (below)

2. I am not sure from your post but ARE YOU USING A PRESSURE CAP ON YOUR RADIATOR? If so you have made an important decision. You have decided on overflow system rather than an expansion overflow system. Long experience taught me to very much prefer an expansion system. And this is NOT because my Morgan engine's manufacturer, LR. prefers it. (Manufacturer's write their Manuals before they have experience with their engine..they call the mistakes they make "Bulletins" which we never get or read if we do... You should have a blanking cap on the rad and a pressure cap on the remote reservoir.

3. I am not a fan of higher rated pressure caps..though 1 extra psi is not much. Raising pressure increases the strain on everything in the system, the hoses, the joints, the gaskets, the clamps, the coolant pump and thusly increases the risk of leaks. I am curious. What was your goal? Or was it merely easier to get this cap? I can understand the last.

Lorne

The TRE caps, which seem to be fitted as standard on most CX Mogs, are not great quality. I've also replaced both of my expansion tank pressure caps with Motorad 16 psi, which is what the factory now seems to use (based on what I saw last time I was there); the cap is nominally rated 16 psi, they will open between 14 psi and 18 psi.

Where the point of shear in the photo has taken place the steel doesn't look very meaty & there's possibly some corrosion too - not good for only 3 years use