bypass hose - yes or no
Turbo Mini Forums

Do you connect up the bypass between the head and the water pump or plug it off?

It seems a bad thing overall since it not only bypasses the thermostat (a good thing before opening temperature is reached) but also the radiator (a bad thing once engine reaches temperature as some flow will continue to bypass the radiator and thus hot coolant is circulating back into the block without going through the radiator).

1275 with Back Door Turbo

Hi,
I've not ran one for years, however the MPi has one built in to the bottom hose.
Like you say it allows for quicker warm up, good for emissions, but recirculates hot water, not so good for power.
So you can guess why it's fitted to start with
Cheers,
Gavin :)

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i think the common thing on here is no bypass as metty turbos disnt have them, i also think a few/ most (lol not sure) drill a few small holes in the thermostat

no longer a series, but still 1.3 turbo.

H,
Mettys have the expansion bottle to recirc through
Cheers,
Gavin :)

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I run no bypass with 6 x 1/8" holes drilled in the thermostat, havent had any cooling issues.
Shane

i use the 74f thermostat

Edited by jimmy on 26th Aug, 2008.

1293 Turbo mini

The Metro uses the flow through the heater matrix as a substitute for the bypass hose.

from what i understand the bypass hose allows circulation of water wilst the thermostat is closed. if you do with out it then you should either, 1. fit the metro heater take off to the the thermostat. 2. drill a couple of holes in the thermostat, or 3. fix the heater tap permanently open.

i used to drill the thermostat but it really is a bodge as it stops the thermostat from doing its job. fitting the metro pipes takes up space in the engine bay, so i opted for permanently fixing open the heater tap. this also supplies water to the turbo so the heater works a little better.

i dont run a bypass hose i run with a 72 stat and 6 holes in it. it warms up fine i use a super 2 core and dont have any problems with cooling i do have an extra fan on a switch just incase

"Tuning should be a compromise between what is possible and what is necessary"

10)Thou shalt always quest for more power

Interesting that no one posted that they have the hose connected.
Thanks for all the replies.
I'll run without it and just keep the heater on all the time - which I've been doing anyway.

1275 with Back Door Turbo

I connect it! However it's OK that its not there as it does fail over time. I guess with all the frequent head gasket changes on the turbo guys this doesn't really matter

Holy thread revival.

My car is being tricky to keep cool - BMW head, dry decked, cinq rad and good fan. Theory is that the water is taking the path of least resistance via the SC thermostat adaptor straight back into the bottom hose instead of circulating the full system. Rad does get warm so not a sticking thermostat though.

As I have 6mm ID feed from head to expansion bottle anyway is it even needed? Thinking I might just stick a clamp on the bypass hose for now and see if that cures matters, if so blank it off completely.

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Edited by minimole23 on 3rd Jun, 2021.

Not something daft like an air lock is it?
Out of curiosity (and off topic) is the clutch housing the only breather that you run on the engine?

Shane

Think I’m clear of air locks, even had it up on the ramp to tempt air residual bubbles out.

I have breathers all over the place. Dizzy hole, head, oil drain and clutch cover. All collect in the catch tank.

Could you pop a restrictor in the bypass line to reduce the flow? something like a piece of round bar with a hole?
How do you have the radiator piped?

Shane