Morris Minor Owners Club

After seven years off the road I'm trying to get my car in working order again and hoping to attend the Birmingham MMOC branch rally at Sandwell Park Farm this weekend. Unfortunately my car keeps overheating, at least I think it's overheating. After driving it around town for 20 minutes it will spew a load of water out of the radiator filler cap. I replaced the thermostat. I've flushed out engine, radiator and heater using Radflush and a hose pipe so I don't think there's any blockage. I've checked the fan belt and that seems okay. I ran the car for 30 minutes at a fast idle when doing the Radflush and it didn't boil.

I'm at a bit of a loss as to what to do next. I'm thinking that the water pump might be at fault but I can't really understand how it could be the cause of the problem - it just spins round and moves the water, right?

Any ideas gladly appreciated, thanks!

It's not unknown for the impeller on the pump to rot away - especially on a car that has been standing. Otherwise - could be head gasket, although I would expect that to produce 'bubbles' in the rad all the time when idling. I would pull the water pump for inspection.

Thanks for the suggestion. I'll give that a try today!

In my experience flushing rarely does much. I had a similar problem some time ago with another car and the solution was a re-core. My current Moggie has a re-cored rad and I drive all day in the aussie heat with no probs.

I wouldn't expect a failed water pump to give overheating problems - it could, but it's not the first place I'd look. It sounds very much like the water system is being pressurised so I would get a compression check done to confirm if the head gasket is OK or not. Then remove rad and water pump for inspection.....

Does the car have a heater? If so, are both hoses getting hot? this should give you an indication if the pump is working or not.

Thanks for the suggestions. The heater does eventually get hot so the pump must be having some sort of effect. I remember when I did the Radflush and left the engine idling for 30 mins, a moment after I turned the engine off it bubbled up out of the top of the rad. I have someone lending me a gizmo this weekend that you fit on the rad that will detect CO2. He says that I should know straight away if it's the head gasket from that. My current thinking is that if this was overheating I would get clouds of steam - I don't get that.

its really very simple to check the pump and head gasket,let the engine get to temp at idle, with the rad cap off.then (keeping out of the way)rev the engine while watching the water inside the top of the radiator,you should see the water level drop slightly as the pump draws water through the system,if it blows out of the top then the gasket is suspect,if it simply bubbles out at idle then suspect is blocked rad or stuck thermostat.if nothing happens at all the suspect pump but 99% of the time its never the pump.Themostats are the usual after a long time laid up.Good luck

I replaced the cylinder head gasket - still overheating. I'm now thinking the radiator isn't providing enough cooling. What's the recommendation? Have a new core put in the existing radiator (I have a quote for £50) or replace it with a completely new radiator (they seem to be around £80)?

I'd go for a re-core over a new pattern radiator, especially if you can get it done that cheaply - IME the new ones don't always fit as well as an original one.

BTW another possible cause of overheating is blocked water passages between the block water jacket and the head. If you take the head off you can clean the scale out by running a drill bit into each one.

Or try a good flushing with Drain Cleaner in the system - just don't leave it in there too long, and flush it well with lots of water afterwards.

Thanks for all the advice. In the end I purchased a new radiator because I needed to get the job done quickly to use the car and didn't have time for a re-core. Based on this experience I would agree with the comment here that recore is probably way better than a new radiator. The new radiator is about 1/4" too narrow so I had to pack it out with a couple of thick washers either side. The hose connections don't seem to point in quite the right direction. There's no drain tap. There's no clip for the overflow hose on the side of the radiator (the old one was welded to my original radiator).

It's a shame because a little more attention to detail in the manufacture of the new rad would have made it just as good as the original one.

It did solve the problem though. No more overheating.

Great success!

Yes in my experience all the flushing and cleaning in the world doesn't fix a claggy old rad. A re-core or a new unit makes such a difference! Good work!