Hello all,
I have replaced my 998 engine with a bypass hose with a 1275 without one. I am not running the sandwich plate heater output either, I am running the normal older heater tap on top of the head.
I recall someone telling me that I needed to drill holes in the thermostat. Is this correct? Shouldn’t the heater circuit allow water flow anyway = from pump through head through heater back to cold inlet into the pump?
Matt
Air lock in the heater perhaps?
Wouldn’t drill the thermostat UNLESS you’ve blanked off the bypass hose.
The hole problem is that I do not have a bypass connections on the water pump or head! So I do need to drill the thermostat?
Matt
> The hole problem is that I do not have a bypass connections on the water pump or head! So I do need to drill the thermostat?
Matt
Can anyone shed more light on this please as I am worried now as about to do my engine swap.
The bypass shouldn’t effect the heater, the water should leave the engine without passing through the thermostat and returns via the bottom hose so the pump pulls it through the heater. If the thermostat was stuck open the engine, and heater, would take a very long time to warm up. An airlock or a blocked heater valve are also possibilities.
A few small holes drilled in the outer disc of the stat lets a bit of water circulate past it so it can sense the temperature. don’t overdo it as the water goes through the radiator and will effect engine warm up.
YES you do or it will overheat drill 6x 4mm holes at least, your heater problem is probably due to a air lock or a stuck heater tap on the block, take filler cap off the rad
and start up the engine get it hot and then feel the heater pipes they should be getting hot if they do then airlock has gone. don’t forget to replace filler cap
You dont need to drill any holes in your thermostat!!! especially not 6 X 4mm holes, as this will cause hot spots on your head, you might as well not be using a thermostat.
Whilst stationarry run the engine with the rad cap off, the you will probably see the water level drop down after a bit, then top it up and it should all be going sweet again.
Im guessing when filling up the rad you filled it up quite fast?
> You dont need to drill any holes in your thermostat!!! especially not 6 X 4mm holes, as this will cause hot spots on your head, you might as well not be using a thermostat.
Whilst stationarry run the engine with the rad cap off, the you will probably see the water level drop down after a bit, then top it up and it should all be going sweet again.
Im guessing when filling up the rad you filled it up quite fast?
Thanks for clearing that up for me, does anyone know when going from a 998cc to a 1275cc are there any benefits in the heating system? ie hotter due to 998cc rad being used? Heating works quicker etc?
I beg to differ go to calvers corner and hear it from the master himself I know who I trust
I don’t know if Tom read that you have no bypass, you will need a few holes in the stat.
The bypass inlet on the water pump is a fair bit less than the 1/2 inch hose that fits it. Even using 1/2", pi r squared says just 4 x 1/4inch holes will be as big.
My setup and not sure if it will work:
Radiator Top –> Thermostate Housing–> Head –> Head heater outlet tap –> in car heating matrix in1
In car heating matrix out1 –> T junction in bottom rad hose–> bottom rad hose to radiator bottom and other end to water pump out which draws its source from the head.
just go with Ethels advice and you won’t go wrong he knows what he is talking about,Tomf clearly didn’t read your post
Thanks for the help.
Some other people also told me about 4x4mm holes are sufficient. It would seem that the water should flow throught he heater when the thermostat is not open, but doesn’t without a small amount of flow through the thermostat - due to the thermo-cyphon nature of the mini cooling system!?
FYI. The heater valve is brand new and operating normally, There may be a vapour lock in the system but unlikely as the mini did the entire show seaon last year without any problems?
I’ll let you know if I get it working.
Matt
I still dont know what my situation is!?
Best way to think of it is that the pump draws water in through the bottom hose and pushes it in to the engine. The engine heats the water so the heater should go between the engine (cylinder head) and bottom hose. The thermostat restricts flow through the radiator until the engine is up to optimum temperature, if you want a heater to demist 'n defrost windows then the heater needs to be on the engine side of the thermostat or it won’t get hot until the radiator does.
> Best way to think of it is that the pump draws water in through the bottom hose and pushes it in to the engine. The engine heats the water so the heater should go between the engine (cylinder head) and bottom hose. The thermostat restricts flow through the radiator until the engine is up to optimum temperature, if you want a heater to demist 'n defrost windows then the heater needs to be on the engine side of the thermostat or it won’t get hot until the radiator does.
so I am going to have to put a few holes in my thermostate?
I was told by people on here that id I drilled out the missing heater outlet on the metro 1275 head then it will all be fine, its connected up how my 998cc was and that never overheated and was allways had hot air when I needed it?
Yes, fitting the heater tap to the driver’s side of the head is fine for sorting your heater, but you still need some sort of bypass (holes or hose) to get the water to circulate around the 'stat - if you don’t the engine is liable to overheat before the 'stat opens.
> Yes, fitting the heater tap to the driver’s side of the head is fine for sorting your heater, but you still need some sort of bypass (holes or hose) to get the water to circulate around the 'stat - if you don’t the engine is liable to overheat before the 'stat opens.
how many holes of what diameter?
I’d try three or four 5mm holes (in the disc bit), you can always add more if needed
Maybe we can learn something here about checking the odvious.
I checked it all out at the weekend and all components were fine, but I did remember cutting the end off of the heater control cable once. Which upon checking has made it too short so not allowing the valve to open sufficiently and the flow was too low to notice.
New cable = open valve and lovely heat.
Thanks for help and advice.
Matt
