Has anyone else on here used a remote thermostat, you know the ones , a housing with 3 hose inlets on it?
It seems that you have an input from the block, an output that opens at temp. to the rad & a bypass connection that circulates coolant past the stat.
I've been trying to do a bit of research on the coolant plumbing using one of these, but have'nt come up with much.

The question is simple.
All the information I have seen ,seems to suggest that the bypass connection should flow through the heater matrix circuit.
In my mind this is a relatively narrow bore to push all of the coolant through, prior to the stat opening.
What do you think?

Are you using the Rover Vitesse style housing? I used one of these as a remote thermostat and the main inlet and outlet matched my 32mm Toyota hoses. The bypass circuit connection was more like 18mm in diameter which would imply that is fine for the purpose.

Oh and I've installed a similar thermostat housing in an Elises to help with the head gasket issues and again the main connections were 32mm and the bypass 18-20mm.

The purpose of the by-pass is two fold
(1) to circulate coolant durring the warm up period to allow the thermostat to open.
(2) When fully warm to re-circulate enough coolant around the lower part of the engine to avoid over cooling.

A few different variations on by-pass plumbing exist, but for a cast iron block engine 5/8" or 1/2" bore by-pass pipe wprk is the norm.

here is the URL for some good info.
http://web.tiscali.it/elise_s1/

The engine would reach operating temperature faster with the coolant circulating in a "relatively narrow bore". The idea is to keep SOME coolant passing over the thermostat so it responds when operating temperature is reached.

Thanks for the replies
The housing is from a 3 series BMW I believe.
All of the hose connections are 34mm. So I guess I'll have to fit a reducer to the bypass circuit to bring it down to the heater matrix bore size.
I'm guessing that if I did'nt fit a heater, this bypass would just go straight back to the pump.
My only initial concern was that the flow through the heater matrix would be too restrictive, but after thought, I suppose this may be a good thing as the engine should reach operating temp. quickly.