Morris Minor Owners Club

Posted: **Sun Aug 31, 2025 12:34 pm**

My engine has been completely rebuilt and totaly cleaned inside using citric acid also. That’s why I‘m sure there is not any debris or corrosion inside the water or oil channels. This engine is like a new one right off the fabric. So the difference in temerature is real.

Chris

Posted: **Sun Aug 31, 2025 12:39 pm**

MMT1968 wrote: ↑Sun Aug 31, 2025 12:34 pm My engine has been completely rebuilt and totaly cleaned inside using citric acid also. That’s why I‘m sure there is not any debris or corrosion inside the water or oil channels. This engine is like a new one right off the fabric. So the difference in temerature is real.

Chris

Yes. This is why some people who have cars with the later square heater leave the heater tap permanently open. The heater air baffle can be put in the off position so it doesn't result in an excessively hot car inside in summer but it is said to improve the water flow to the back of the engine.

Stephen

Posted: **Sun Aug 31, 2025 1:22 pm**

That’s why I have a seperated heater valve installed that is connected to the heater tap by a piece of hose. (Visible on the pic). That pic was taken prior to the installation of the shunt and the electric booster pump.
I have tried before to go on with the heater tap open but this didn‘t reduce the temerature at the rear end of the head sufficiently. It was a difference of just 2°C.
I use a Davies Craig EBP25 booster pump but any other booster pump will do also.

Chris

Posted: **Sun Aug 31, 2025 7:42 pm**

I have fitted a 3 way valve on my van. Water is either going to the heater when needed or straight back around the engine. It works really well. In the hot weather I can get fresh air into the car via the heater, knowing the water is recirculating around the engine

Posted: **Sun Aug 31, 2025 9:00 pm**

Right. My system works similar but there is a steady circulation by the electric booster pump via the shunt back to the heater outlet hose. The heater is switched on when needed only by the seperate heater valve behind the shunt. So I only have to decide if I need the heater or not. The flow of coolant is improved steadily.

Chris

Posted: **Mon Sep 01, 2025 9:03 am**

Interesting quick release rocker cover nuts that Chris has in his photo. I can't envisage a situation where it would be necessary to undo those in a hurry witrhout having some spanners to hand. Nothing wrong with them, just unusual.

Posted: **Mon Sep 01, 2025 9:21 am**

Well, I have a set of spanners and screwdrivers on board, always. Just in case.

Chris

Posted: **Mon Sep 01, 2025 9:41 am**

simmitc wrote: ↑Mon Sep 01, 2025 9:03 am Interesting quick release rocker cover nuts that Chris has in his photo. I can't envisage a situation where it would be necessary to undo those in a hurry witrhout having some spanners to hand. Nothing wrong with them, just unusual.

I've not seen those before. Yes, if you need to access the rockers you would presumably have tools at hand to adjust the rocker gaps!

Stephen

Posted: **Mon Sep 01, 2025 10:03 am**

I‘ve got them at a Mini racing shop and liked them. I check the valve gap regulary and have my 0,35 gauge on board also. My cam needs 0,35 in and out.

Chris

Posted: **Mon Sep 01, 2025 10:09 am**

MMT1968 wrote: ↑Mon Sep 01, 2025 10:03 am I‘ve got them at a Mini racing shop and liked them. I check the valve gap regulary and have my 0,35 gauge on board also. My cam needs 0,35 in and out.

Chris

Presumably that is 0.35mm or 13.78 thousandths of an inch? For Imperial feeler gauges that would be the nearest whole number, 14 thousandths of an inch.

Stephen

Posted: **Mon Sep 01, 2025 10:15 am**

Right!

Posted: **Mon Sep 01, 2025 10:18 am**

I have a pair of those tee handle rocker cover "nuts". Bought them years ago and never used them. They're stuffed into a spare rocker cover.

: rocker cover.jpg (163.28 KiB) Viewed 3906 times

Posted: **Mon Sep 01, 2025 11:17 am**

My 1275 Marina engine has 78Kw which is almost double the power the original 1100-engine has so I like to check important parameters regulary. That means checking the valve gap almost every 2000 km as well as changing oil every 5000km.

Chris

Posted: **Wed Sep 10, 2025 7:52 pm**

A final follow up on the overheating, I did remove the block drain plug and sure enough no water came out, after 10 minutes digging sludge out water flowed out freely, filled with citric acid solution and left to clean out, flushed several times and now running far cooler. The new radiator cap had no rubber seal so I managed to find one suitable, now not suffering any coolant loss even after long runs on hot days so I think all is now finally resolved, thanks for all your suggestions and help.

Posted: **Wed Sep 10, 2025 8:42 pm**

May I ask what you managed to use to dig the sludge out as I have tried all sorts, unsuccessfully, and
I've personally run out of ideas.

Many thanks

Graham.

Posted: **Wed Sep 10, 2025 8:54 pm**

cswagon1 wrote: ↑Wed Sep 10, 2025 8:42 pm May I ask what you managed to use to dig the sludge out as I have tried all sorts, unsuccessfully, and
I've personally run out of ideas.

Many thanks

Graham.

This has been discussed on here many times and if you search the forum you should find lots of ideas.

Personally, I used a combination of long screwdrivers and coat hanger wire. Phil has posted pictures of a cutaway of the block. It helps to have seen this so that you can visualise in your mind what you are poking at and bend your coat hanger wire to suit.

viewtopic.php?p=636733&hilit=unblocking+drain#p636733

viewtopic.php?p=618388&hilit=engine+block+drain#p618388

Stephen

Posted: **Wed Sep 10, 2025 10:09 pm**

MMT1968 wrote: ↑Sat Aug 30, 2025 2:11 pm Another point,

I found a reasonable difference in engine temperature between the front end at the termostat housing and the back end at the heater outlet. In my car that difference was 20° C. So if at the front 80° it’s at the heater outlet 100°C. To my opinion that’s a lot and too much. Could be that this is the reason for the often damaged 3rd cylinder if the head gasket fails. That cylinder is the first at the hotter end and has the smaller rim to the 2nd cylinder. So this one may be the hottest of the four and thus more in danger than others.
I solved that partly by a shunt between the heater outlet hose and the back flow hose coming from the heater unit.
The temperature difference dropped by that about 8°C. To me that seemed not enough so I installed an additional electric water pump in the hose from the heater outlet towards the heater unit before the shunt and used a seperated heater valve mounted after that shunt.
That works sufficiently as the difference went down to 5°C.

Chris

There is no water circulation to the rear of the head when the heater valve is closed. I fitted a heater valve fron a London taxi which has a bypass valve in it, so there is always flow even when the heater is off.

Posted: **Wed Sep 10, 2025 10:10 pm**

I have a 1275, and have always run 88°C thermostats, even when I had a 1098 in. Had no issues with overheating, even in France and Italy last year on long runs in 35°C.

Posted: **Wed Sep 10, 2025 10:24 pm**

ndevans wrote: ↑Wed Sep 10, 2025 10:10 pm I have a 1275, and have always run 88°C thermostats, even when I had a 1098 in. Had no issues with overheating, even in France and Italy last year on long runs in 35°C.

Actually I was just reading on the Minispares website that the 88 degree thermostat was fitted to 1275 Minis between 1988-2000. Apparently the 74 degree thermostat was fitted to Minis pre-1981. Different car and cooling of course but same A-series engines.

Stephen

Posted: **Thu Sep 11, 2025 6:46 am**

Just to make clear, my engine is completely rebuild from bits and pieces. All oil or water channels cleaned and the oil gallery as well. Additionally it has been flushed with citric acid. A new water cooler is installed as is a stronger water pump. All hoses are new. The head is completely ported with bigger valves. At the heater outlet of the head I mounted a ball valve that’s connected to a seperate heater valve by a piece of hose. The thermostat
Is a 88° one and I drilled the bypass hole a little bigger.
That was the case whe I measured the differece in temperature as mentioned above.
The shunt and the electric bypass pump solved the issue almost completely. When the thermostat opens I measure 90° at the front and 92° at the rear end of the engine.

Chris

Morris Minor Owners Club

Running hot

Re: Running hot

Re: Running hot

Re: Running hot

Re: Running hot

Re: Running hot

Re: Running hot

Re: Running hot

Re: Running hot

Re: Running hot

Re: Running hot

Re: Running hot

Re: Running hot

Re: Running hot

Re: Running hot

Re: Running hot

Re: Running hot

Re: Running hot

Re: Running hot

Re: Running hot

Re: Running hot