My A+ head doesn't have a bypass hole. The water pump of course does, but just as a little dag of pipe that is plugged.

Head has no hole for heater either.

Today I drilled some holes in the thermostat as Chong suggested. Cheaply and easily reversed mod, and it was already appart.

But how was is it meant to work?

Or could the head's bypass have been plugged at some stage and I can't see it under the paint?

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"Life is not like a box of chocolates... it's more like a jar of jalapenos. Whatever you do today, may burn your arse tomorrow."

gees chong is becoming quite the expert on modifications now.

as for connecting the hose from head directly back into heater T on bottom hose, you can cool your car by a sugnificant number of degrees by using a heater core in there instead of directly back into the block as it has no cooling other iwse at all.
turn the heater tap off and see if it runs cooler.might only be by 5deg or so but it makes a huge difference when it gets to hot end of the guage.

A+ has no by pass at all it passes thru a sandwhich plate on the bottom of the thermostst housing. which on a mini doest fit in with the set up we already have.

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Doc, not sure about the comments on the setup shown in the photo (posted by minimad). It shows the head take-off returning to the top of the radiator, not the lower hose (and hence the block), so this is the correct way to do it if there is no matrix in the line. My 850 runs a set up the same as the pic (except I T'd into the top hose rather than directly into the rad), my 1380 is the same as cranky describes: head take-off goes into heater matrix mounted in grill, then to the lower hose.

Just my ten cents' worth:

If you have ever had a bypass hose burst on you in the middle of nowhere - read here anywhere not within walking distance to professional help - and you have to try and pry your spare bypass hose (which of course, you carry religiously, just for such an occasion) into place, with the head still attached, then you will never (and I mean NEVER) want to have a bypass hose on any engine, ever again.

Trust me, this is not a fun job on the side of the road, or stuck in the bush somewhere.

My engines never have bypass hoses, anymore - doing this job once was enough. Thermostats are always drilled, and the car rarely overheats - except on 40+ degree days with hot north wind against the radiator, usually half way to Sydney or somehwere....

But, I think I'm rambling now.....

Cheers,
Watto.

If you use a bypass hose, forget the convoluted rubber ones- they are poorly made these days and prone to failure.

Cooper S had a straight piece of 1/2" heater hose instead, I've used this for years and never had a failure.
But make it good hose- either Gates or Dayco (both US made).

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Echo what Watto and the Doc said....but if you do have a bypass hose fitted of any description and you don't plan to remove it for some time...then I would carry a convoluted rubber one as a spare to get you out of trouble.....because thats what they were invented for....changing the bypass without lifting the head.

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"Show me the Mini!"

How does this sandwitch plate work? Lets some water by the thermostat?



But the bypass should have nothing to do with the car overheating. It should only be in the circuit when the thermostat is closed and the car is cold.

Or do you mean that drilling the thermostat has some effect on hot running performance?

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"Life is not like a box of chocolates... it's more like a jar of jalapenos. Whatever you do today, may burn your arse tomorrow."

Zizzle
The role of the bypass hose is that when the thermostat is fully closed and the engine is running (warming) then the water trapped in the head will expand (and even get close to boiling) before the thermostat opens.

The bypass hose and the holes drilled in thermostat allows this expanding excess to escape into the general coolant.

Just on that note ; currently, cheap thermostats are made in Asia and are of terribly variable quality. Some open far too early and others dont dont open until virtually boiling. Check any new ones you buy with hot water and a thermometer before you fit it or only buy the good known brands.

The thermostat has no performance effects on a warm engine except to perhaps close slightly should the water temperature in the head begin to cool too much. Its there specifically to help a cold engine get to a reasonable operating temperature.

You do, however, need a thermostat (or a restrictor plate) to slightly slow the flow of water and help prevent the water pump cavitating in the coolant.

Be very careful with Clark rubber products. A lot of their stuff is really useful, but much of it (particularly the chair ends and stoppers) is natural latex rubber, which breaks down VERY rapidly when exposed to oil or grease

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1958 Morris Minor 1000 - "Nigel"

Yes , i was going into the top tank like the photo....sorry.

But from what has been said, I will still need those holes to flow the hoter water around the thermostat to get it to open

Minimad

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You can take the boy out of the racer.........but not the racer out of the boy!

maybe some one that knows what they are doing should write this up for the how to section

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