stuffedpike20 wrote: ↑Wed Jun 24, 2026 7:43 pm
Voice of doom here.....
A few weeks ago I accidentally nudged the heater knob with my knee as I got out of my minor. I never touch the heater knob, and always leave it open all year round because I know they can be a problem.
Next time I used my minor I went to my local tip....a round journey of less than a mile. When I got home, I found that most of the coolant had gone from the radiator.
Just nudging the control knob with my knee had been enough to make the heater valve start leaking, and I was surprised how much coolant had been lost in such a short journey.
I fitted a new valve, and now all is well.
This has happened to me too. I was waiting at traffic lights when all of a sudden, huge clouds of steam were billowing from the bonnet along with the horrible smell of antifreeze burning on the hot exhaust manifold. I lost almost all of the coolant. Fortunately, a kindly person gave me a bucket of water and I was able to bind the valve back together with cable ties. I made it home without further incident and fitted a new valve.
Stephen
1969 1098cc Convertible “Xavier” which I have owned since 1989.
Only time I’ve ever experienced fuel evaporation was during a trip to Arizona a couple of years back… we hired a modern car, but quickly discovered that best method was topping up was little and often, because it just evaporated out
My Minor 1000 is a nice simple earlier one which has a brass tap rather then a new fangled leak-prone valve
One less thing to go wrong - although they can sometimes seep a little coolant of course.
I drove just over 100 miles today. Fast dual-carriageways, country roads, steep hills (the South Downs), one traffic jam for 15 minutes. Around 35 C. The car was absolutely fine. No issues whatsoever. I, on the other hand, felt like I was about to melt!
Stephen
1969 1098cc Convertible “Xavier” which I have owned since 1989.
Nellie was fine, I was half done, my friend who I was meeting ran late so I had to wait in the car and by the time he pulled up in his air conditioned EV I was basically a puddle,
One thing I have noticed, and I don’t know if it’s heat related or not… but over the last couple of days Nellie’s fuel pump has been making a different sound when I put the ignition on… more a brrrrr… instead of tick tick. Everything looks normal though, and she is starting and running perfectly? I can hear the fuel pump ticking as normal while driving too… it’s just that initial sound?
Probably the fuel in the carb float chamber evaporated so the pump is going 'hell for leather' to fill it again. If it slows to a steady Tick Tick after about 5-10 seconds then it's normal.
My Morris met a Mini in Chiddingfold, Surrey today. Naturally I got chatting to the owner and we had to look at each other's engine bays of course. Basically the same A-series engines but in the Mini, a much smaller engine bay and a tiny radiator mounted sideways. Neither of us had any overheating issues. The Minor is so obviously very generously cooled in comparison to a Mini but the Mini had no issues in 35 C heat either. We worry too much!
Stephen
IMG_3522.jpeg (3.14 MiB) Viewed 4056 times
1969 1098cc Convertible “Xavier” which I have owned since 1989.
geoberni wrote: ↑Sat Jun 27, 2026 5:14 pm
Probably the fuel in the carb float chamber evaporated so the pump is going 'hell for leather' to fill it again. If it slows to a steady Tick Tick after about 5-10 seconds then it's normal.
svenedin wrote: ↑Sat Jun 27, 2026 6:14 pm
My Morris met a Mini in Chiddingfold, Surrey today. Naturally I got chatting to the owner and we had to look at each other's engine bays of course. Basically the same A-series engines but in the Mini, a much smaller engine bay and a tiny radiator mounted sideways. Neither of us had any overheating issues. The Minor is so obviously very generously cooled in comparison to a Mini but the Mini had no issues in 35 C heat either. We worry too much!
Stephen
IMG_3522.jpeg
I love meeting other classics when I’m out and about! Instant friends
In the upper 80’s today with 100 in the Thursday forecast. The pickup is boiling after idle for a few minutes. The upper hose is hot but the bottom is not. Hoping its a bad thermostat. Would a bad thermostat allow the top hose to get hot? Conduction vs convection? Looks like a recently replaced pump. I had hoped that this purchase was going to be turnkey. Gas it up and drive.
The carb jet was frozen and the throttle shaft badly worn. Cleaned everything, freed the jet and replaced the shaft but still running rich? Couldn’t get the needle out to identify. Plastic float. Adjustable?
Very disturbing piston #1 is at BDC when timing mark is at 0* mark? Were there crank pulleys and chain covers with timing marks at the top? Had to put my timing light on spark plug #2. I really don’t want to start tearing everything apart.
59Elva wrote: ↑Tue Jun 30, 2026 9:36 pm
In the upper 80’s today with 100 in the Thursday forecast. The pickup is boiling after idle for a few minutes. The upper hose is hot but the bottom is not. Hoping its a bad thermostat. Would a bad thermostat allow the top hose to get hot? Conduction vs convection? Looks like a recently replaced pump. I had hoped that this purchase was going to be turnkey. Gas it up and drive.
The carb jet was frozen and the throttle shaft badly worn. Cleaned everything, freed the jet and replaced the shaft but still running rich? Couldn’t get the needle out to identify. Plastic float. Adjustable?
Very disturbing piston #1 is at BDC when timing mark is at 0* mark? Were there crank pulleys and chain covers with timing marks at the top? Had to put my timing light on spark plug #2. I really don’t want to start tearing everything apart.
The thermostat will allow some water to pass even if it is stuck shut because there are some holes to allow air to pass when filling with coolant. So yes, a failed thermostat stuck shut can cause the symptoms that you have.
Take the spark plug out from cylinder number 1 (the one at the front nearest the radiator) and put your finger over the spark plug hole whilst turning the engine over on the starting handle. When you are on the compression stroke you will feel air try to push your finger off. You can roughly work out where TDC is by carefully putting a screwdriver down the spark plug hole and feeling the piston rise to the highest point. Now look at the timing marks. The timing marks are on the timing chain cover underneath. It is possible that a non-original pulley has been fitted which has a timing mark designed to line up with the timing marks above the timing chain cover as used on later A+ engines.
Stephen
1969 1098cc Convertible “Xavier” which I have owned since 1989.
Thanks Stephen,
I did the screwdriver trick. The 1275 in the truck doesn’t have the handcrank spigot so I had to use both hands to tension the belt and turn the fan. It might not be exact but it’s close to 180* out of time. If I have to pull the radiator I’ll have a closer look at the pulley and maybe add a crank handle spigot if I have one in my spares collection. I vaguely remember timing marks on the cover above the crank but maybe that was on a B series motor. MGA/MGB.
Bill B
59Elva wrote: ↑Tue Jun 30, 2026 10:24 pm
Thanks Stephen,
I did the screwdriver trick. The 1275 in the truck doesn’t have the handcrank spigot so I had to use both hands to tension the belt and turn the fan. It might not be exact but it’s close to 180* out of time. If I have to pull the radiator I’ll have a closer look at the pulley and maybe add a crank handle spigot if I have one in my spares collection. I vaguely remember timing marks on the cover above the crank but maybe that was on a B series motor. MGA/MGB.
Bill B
Definitely have a look at the pulley. If it is a harmonically damped pulley it may have been intended for a later engine, A+, that has a timing cover with timing marks above. The pulleys are interchangeable on earlier A-series engines but the timing notch in the pulley will be in the wrong place. To mark the pulley with the notch in the correct place you could use a dial gauge to set the engine at exactly TDC and mark the pulley where it lines up with the TDC pointer. Or you could fit the correct pulley.
Stephen
A-Series timing chain cover
IMG_2473.jpeg (368.36 KiB) Viewed 2496 times
A+ series timing chain cover
IMG_2717.jpeg (3.72 MiB) Viewed 2496 times
1969 1098cc Convertible “Xavier” which I have owned since 1989.
I got the thermostat housing off with copious applications of PB Blaster and a little percussive persuasion. The thermostat is marked “Wahler W. Germany and 82. I assume 82*C/180F. I didn’t want to fight the air conditioner but put a pot of water on the stove. The thermostat just started to crack open at 88* but didn’t fully open until the water was starting to boil at about 98*C. Inconclusive. Did prying it out unstick it? Is the green crystal crud pervasive throughout? I’ll replace the thermostat. Would a 160* (71C) be a better choice? The truck won’t be driven in the winter.
Does the center punch mark on the head stud indicate a high compression engine? Maybe just high compression studs?
Yes it's an 82 Centigrade thermostat which is perfectly satisfactory. I think your tests showed it is faulty and should be replaced.
The Minor is overcooled (it has a large radiator relative to the size of engine). If you fit a cooler thermostat, e.g 71 C, then the engine will take a long time to warm up. Engines actually run better when they are at optimum temperature and too cold is not efficient.
I would be concerned about all of the green crystalline coolant residue. This shows that the wrong type of antifreeze was used and it was unsuitable in a classic engine. In the UK the recommendation is Bluecol which is ethylene glycol. Do not use OAT or HOAT antifreezes. Colours of the various antifreezes are not reliable indicators of what the antifreeze contains in different countries but in the UK, Bluecol is you've guessed it, blue.
I think you are going to need to flush out all of the antifreeze residues as best you can. Unfortunately, it may be blocking some of the waterways in the engine block or the core of the radiator. Perhaps with the correct thermostat and the water pump circulating hot coolant properly these crystals will dissolve. If it was me I would fill up with plain water, run up to temperature, drain and repeat at least several times. I would also take the radiator out and flush it repeatedly with a hose pipe.
The dimpled stud usually indicates a high-tensile stud. Sometimes the mark looks like a Y.
Stephen
1969 1098cc Convertible “Xavier” which I have owned since 1989.
Thanks Stephen. I’ll have to research coolant next time I’m at the parts store. Years ago there was a move away from ethylene towards polypropylene glycol as being more pet friendly.
A new conundrum. Water poured into the radiator runs out the open petcock. Water poured into the head at the thermostat opening does not drain down at all!?? Admittedly there is only about 4 inches of head between the thermostat and the lower radiator hose but no leak down?
I guess the next step is pulling the radiator and maybe the water pump. I can’t see how the head gasket could be incorrectly installed. If the truck was running previously I can’t explain the sudden problem. Internally collapsed hoses.
59Elva wrote: ↑Thu Jul 02, 2026 5:36 pm
Thanks Stephen. I’ll have to research coolant next time I’m at the parts store. Years ago there was a move away from ethylene towards polypropylene glycol as being more pet friendly.
A new conundrum. Water poured into the radiator runs out the open petcock. Water poured into the head at the thermostat opening does not drain down at all!?? Admittedly there is only about 4 inches of head between the thermostat and the lower radiator hose but no leak down?
I guess the next step is pulling the radiator and maybe the water pump. I can’t see how the head gasket could be incorrectly installed. If the truck was running previously I can’t explain the sudden problem. Internally collapsed hoses.
It sounds like that crystalline antifreeze gunk is blocking the waterways in the head and block. Given how much of it there was in the thermostat housing it would be easy for it to block the water passages. There are ways around this. If you remove the block drain plug and connect a garden hosepipe to the heater outlet (heater hose and garden hose happen to be the same inside diameter) you might be able to flush the gunk out. Obviously remember to open the heater tap. Trouble is, the block drain is almost always blocked and takes some considerable effort to free up. You can search on the forum for how to do this but a coat hanger unbent and used as a drain rod works eventually.
Stephen
1969 1098cc Convertible “Xavier” which I have owned since 1989.
There were flush kits that employed some kind of acid on the market years ago. Don’t know if they still exist given the growth of environmental regulations over the years. Also don’t know if they were compatible with alloy components. The sun and 94*F humid air is limiting my time in the driveway.
The radiator is out. If I blow up the lower hose I get some bubbles at the thermostat but no water drains back out. I might try hooking a shop vac to the hose to see if I can suck down some water from the head.
