Coolant bypass

notjustair · Dec 17, 2013

Saw the post on radiators below. I have always considered narrowing the coolant bypass on my M.

So is that piece cast? I don't recall ever looking at it close. Just wondered if I need a cast rod or anything. Anyone done it? How much should I leave open in that channel when I start welding? The hardest work mine does is feed grinding, but it is my loader tractor so it runs daily.

riverbend · Dec 17, 2013

I'd try a sack over the radiator before doing something that would be hard to reverse and might be a problem in the summer.

Greg

pete 23 · Dec 17, 2013

I would put a plug in it and then you can drill a hole in plug to size you want. Probably start with about a 1/4 inch hole. When you are doing this , take the thermostat housing off. Put a garden hose in the outlet where it connects to radiator. See how much water flows on through. That is most likely the reason your engines does not warm up. You put a lot of water past most of those thermostats because the housing is corroded out inside. You will notice all newer engines that use the tube style thermostat also have a seal in the thermostat housing to allow only the amount of coolant to flow that can go through the bypass hole in thermostat. Some of those holes are also too large and can be soldered shut and then drilled smaller.

notjustair · Dec 17, 2013

You can't plug them as the bypass for the M is eyebrow shaped. It is approximately 1 3/4 inches long in an arc. Imagine a jack-o-lantern mouth without the teeth.

With a new radiator and water pump I am not too worried about relying only on the main opening in summer. I have an extra housing so that is what I am tinkering with anyway.

I guess I will start with half? It appears to be cast. Is that correct?

pete 23 · Dec 17, 2013

The bypass is the straight cast tube between water pump and thermostat housing with the short hose on it.

Janicholson · Dec 17, 2013

When built, the design wasreflecing the thinking that cold parts last longer. they do not. old oils were self destructing from day one, and cool oil is good for those old oil formulations and cracking methods. Efficiency is driven by heat used to push the piston. The hotter the engine surfaces the greater proportion of the combustion heat is used to push the piston. New oils are happy in the heat.
I would use a grinder to prep the oblong hole, then braze it shut. A .375 hole would be where I would start. Jim

David G · Dec 17, 2013

Jim,

That narrative was amazing.

pete 23 · Dec 17, 2013

Jim, I think he is referring to the crescent shaped opening in the thermostat housing itself, which does indeed lead to the bypass between thermostat housing and water pump. But it would be a lot simpler to plug the round hole than the crescent shaped one he is referring to.

Janicholson · Dec 18, 2013

Rethinking the issue. If the common connection to the engine side of the T-stat is the block through the big rear hole, and the hose connection on the bottom, the circulating water would still be able to get to the radiator (undesirable in large quantities for warmup) if the hose port was restricted. It would also restrict block flow to even out the warming up coolant. What I suggested prevents coolant from getting to the other side of the T-stat in large quantities, where it is cooled too much and never allows the engine temp to be "normal". The best solution (posted above by another contributor) is to use a stainless steel sheet metal blocking restrictor plate between the halves of the housing limiting the flow to the radiator to 3/8. Respectfully, Jim

Coolant bypass

notjustair

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riverbend

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pete 23

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notjustair

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pete 23

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Janicholson

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David G

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pete 23

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Janicholson

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