32 replies to this topic

[the boy howard]

Hi, Im currently building a new engine and fitting a new water pump at the same time. The water pump has the bypass outlet on it and so does the head im fitting (currently blanked off), so my question is would you recommend fitting the bypass or not bother and blank the water pump outlet off aswell (not sure what to use?)?

Is there an advantage/advantage fitting it, not sure what its supposed to do really!?

cheers
lee

[Dan]

The cooling system MUST have a bypass. If there is no other bypass in place, in the form of a heated inlet fed from a sandwich plate or in the form of a drilled thermostat then you absolutely must fit the bypass hose. It's purpose is to allow some coolant to flow before the thermostat opens, reducing load on the pump and stopping the engine developing hot spots as it heats up.

[m1tch]

The answer is yes

also make sure you get good quality hose, don't get the OEM replacement, use 1/2" heater hose

[Dan]

OEM IS a piece of regular 1/2" hose. Those terrible concertina hoses are only made as a temporary emergency roadside repair. They do a good job of a temporary fix but that is all they are for and when people try to use them as a permanant hose they don't last.

[Big_Adam]

I disagree.

It's a stupid designed little pipe. Ditch it and put some holes in the thermostat. Be free of the silly little pipe. Done me good for a year and half now.

[Dan]

And now you have to drill any replacement thermostat you buy. Not good if you break down somewhere thanks to a stuck thermostat.

[Big_Adam]

And now you have to drill any replacement thermostat you buy. Not good if you break down somewhere thanks to a stuck thermostat.

Then I'd take it out, eat the cereal I used to make the new gasket and then drive home.

[Cooperman]

Those nasty little hoses have caused so much anguish over the years that anything that does away with them has to be a good thing. I always build without the by-pass hose and I drill 8 off 5 mm holes around the periphery of the 'stat and that works fine.
As above, if the stat sticks, remove it until you can get and drill a replacement.

[zef]

Those nasty little hoses have caused so much anguish over the years that anything that does away with them has to be a good thing. I always build without the by-pass hose and I drill 8 off 5 mm holes around the periphery of the 'stat and that works fine.
As above, if the stat sticks, remove it until you can get and drill a replacement.

Unless I'm mistaken, and I might just be, but that amount of 5mm holes is like having a 14mm diameter hole in your stat. That must be close to the actual hole the stat has when open. I can understand if it's on a race engine as they run hot but on a 'normal' engine it's probably overkill.

[Cooperman]

Don't forget the by-pass hose is 1/2" diameter.
Anyway, it's always worked for me. I tend to get to build mainly non-standard engines anyway, but even with a standard 1275 engine, they do tend to run a bit on the warm side, so slightly easier water flow won't hurt.
On my own engines I run a thermostat blanking sleeve and that's like having no stat, just a flange down into the stat housing to give a bit of back pressure.
My grandson has a Mayfair 1061 cc and his stat has no by-pass and no holes. It runs fine and has done so for 2 years now.

[Deathrow]

It's alright saying the bypass hose is 1/2" and thats why you can get away with an equal sized hole (made of smaller holes) in the thermostat, but the point is, the bypass hose "bypasses" the radiator, the holes in the thermostat do not. You might as well take the thermostat out and throw it away.

EDIT: I'm not trying to argue with drilling the thermostat, but a total of a 14mm hole is way too much imo.

Edited by Deathrow, 10 September 2009 - 08:41 PM.

[bmcecosse]

Definitely NO! Ban the by-pass hose! It's a nightmare! But I feel one or maybe two 1/8" holes in the stat is sufficient - although as long as the heater valve is kept open - you really don't need any holes. This is ideal in winter - with an 88 degree stat - and gives a nice quick heater action - and really good heater flow!

[Cooperman]

It's alright saying the bypass hose is 1/2" and thats why you can get away with an equal sized hole (made of smaller holes) in the thermostat, but the point is, the bypass hose "bypasses" the radiator, the holes in the thermostat do not. You might as well take the thermostat out and throw it away.

EDIT: I'm not trying to argue with drilling the thermostat, but a total of a 14mm hole is way too much imo.

No, you never throw the thermostat away or you'll risk overheating around no.4 cylinder wall due to the lack of back pressure. You must have either a stat (drilled or otherwise) or a 'blanking sleeve'.
If you've ever seen a works-type blanking sleeve, the hole is the same as the diameter of the stat housing. It has a vertical tubular portion about 1" deep down from the stat mounting face. This provides the necessary back pressure and, compared to a stat with 8 off 5 mm holes around the periphery, the cross sectional area of the hole is massive. However, it works well, but the car is slow to warm up.
Excessive heating-up is the bigger problem than excessive cooling-down on almost all Minis.
I can tell you that my engines with 8 off 5 mm holes do run extremely well, don't overheat and are reliable.

[Big_Adam]

No, you never throw the thermostat away or you'll risk overheating around no.4 cylinder wall due to the lack of back pressure. You must have either a stat (drilled or otherwise) or a 'blanking sleeve'.

Disagree, if you stay within speed limit it's no problem without sleeve or thermostat. Just when you floor it temp starts going up and up. Found that out with my 82' which never had a thermostat. Worked fine but 80mph+ the temp would start to creep up.

Still at least suggest a sleeve at the very least.

[joakwin]

i have a 88 stat with one hole in it and i have the bypass still hooked up, on a 84 998/auto
the car came with the 88, in the summer it was getting to the red on the pod, but that would be when i got home from work

right now that its starting to get cold it runs at the 3/4 mark on the pod,
i got a new 74 deg stat for next summer im gonna try out

personally i would like to see how a vtec cooling system would work out in my car,
but i don't think my wallet is ready for a vtec mini