Morris Minor Owners Club

Recently my 1098 with 12G940 head, maniflow, HIF38 which has performed fine for some years has developed an overheating problem. Even in cool weather temp climbs, electric fan makes no difference and boils over.
Stripped down and thermostat and water pump were fine, rad not clogged, airflow not obstructed. Removed head and saw head gasket as in photos. Does this look like evidence of head gasket leak in early stages?

I will check and report back. All the other waterways look clear and clean.

Did you check for bubbles of gas in the radiator as a first diagnosis? Had the coolant changed colour ?

So easy, zero cost in parts, time and labour.

Was it really overheating or just losing water?(until it would then overheat)

Have you checked the head for cracks? No point guessing, now the head is off.

Hi, rear drain plug clear. Yes the water did appear to contain gas - bit like a geyser really - afraid coolant was pretty murky anyway. No physical signs of damage to cylinder head - what do the photos of the cylinder head gasket suggest?
It's having a head gasket change anyway so I'll do compression test following that...

Most of the staining seems to be coming from the pushrod holes so I would guess it is oil, the coolant ones and combustion rings all look pretty good.

you seem to have checked most of the obvious things If you have coolant flowing no leaks and somewhere to dissipate the heat it should work !, other thoughts:

- the cooling fan is blowing the right Direction?
- was there any water in the oil?
- might be worth getting the head crack tested before you re-fit it, look in the exhaust ports for signs of coolant one with a leak is usually much cleaner).
-ignition timing hasn't drifted miles off?

No signs of cracking in ports or head. Exhaust ports all similar. Plugs and head of pistons were oily on stripping down, but it wiped off.
It will get reassembled - lapped in valves but fine really. They didn't leak when combustion chamber filled with paraffin overnight.
Then I'll check timing..... And report back ... Thank you all.

No signs of cracking in ports or head. Exhaust ports all similar. Plugs and head of pistons were oily on stripping down, but it wiped off.
It will get reassembled - lapped in valves but fine really. They didn't leak when combustion chamber filled with paraffin overnight.
Then I'll check timing..... And report back ... Thank you all.

Was the water definitely moving as the steel impellors on water pumps can corrode off. Also check the condition of the radiator cap, if the seal goes the coolant will boil as it will be at a lower pressure.

Has the head got a bypass or did it have holes in the thermostat?

Hi, water pump on examination did have minor corrosion to impeller vanes however it all worked fine. The thermostat didn't have a hole drilled in it but the head has a bypass hose. Rad cap is a 4.5 lb one which seems in working order but a bit tatty.

A sticking thermostat could also have been the problem. Just another simple check that water is flowing through the rad and being cooled.

The fire rings on that gasket appear good. This is looking more like a wild goose chase, instead of an easy diagnosis with a simple fix.

You are probably running a weak mixture.

Hi

Maybe a silly suggestion, but do check the electric fan is blowing the right way?
I got the wires crossed on my MK2 pusher fan. It was fine on the motorway, but anything below 40 mph and it boiled over very quickly.
Fortunately a quick fix when I worked it out!

Regards
David

Update.... All re-assembled so test flight this evening.
First drive and no change at all. Boiling over even with 7lb radiator cap. Intense frustrated scrutiny followed. Discovered rubber vacuum advance connection to distributor had cunningly failed in two places but no sign from side or top. Replaced item (not a year old).
Second drive better, will still boil over on tickover after drive without the electric fan.
Low on power up hill, no pinking. So thinking now re timing, but also wondering about needle running too lean up the rev range as suggested above.

but also wondering about needle running too lean up the rev range as suggested above.

A very simple check, without dismantling the carb, manifolds, etc would be to run it and check the colour of the plug electrodes after a few miles. Can’t really see that as a problem, suddenly, after several years running OK., mind

Checking the advance/retard needs nothing intrusive. Nor checking if the radiator has a temperature gradient or the bottom hose remaining cold.

Tell us more how you checked the therostat.

Is the radiator cap making a good seal?

John ;-)

So, adjusted timing which was considerably retarded. This improved the overheating.
No boiling over/ water loss as before. Thermostat working ( had been tested previously out of car). Temp gradient in radiator. On return from run put compression tester on - 110psi dry, 120 wet..... New Sealey gauge but assume it's accurate. So does this mean previous boil overs have let it overheat to the extent the rings are shot?.

As regards the rings. Unless you draw the pistons you will not be able to determine if the rings have been cooked.
Personally I would reassemble the engine with a new head gasket, use the car and see what happens over a period of time.
Obtain a set of 'A' Plus head studs and flanged nuts and set the torque to 50lbf ft dry.
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