Can i use vacuum hose between the expansion bottle and the main coolant system, i assume its not under any real pressure since it goes up to the expansion bottle.

And vacuum hose is a fair bit cheaper, and easier to shape than actual coolant hose.

Cheers
Mikkel

it will be under the same pressure as the coolant system, should be reinforced hose really

Your BMW engine wil run a header tank, not an expansion bottle, so it is under pressure, you need to use reinforced coolant hose.

You need hose rated for up to 3 bar internal pressure.

The whole cooling system is under pressure, the only expansion bottles that aren't under pressure are those that are open to the atmosphere and are connected to the overflow from the pressure cap as on many japanese cars.

OK, cheers all,

Im ok to use vacuum hose for the breather from the top of the rad to the header tank then?

quote:

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Originally posted by Miks15
OK, cheers all,

Im ok to use vacuum hose for the breather from the top of the rad to the header tank then?

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OK then cheers

I've managed to use vaccuum hose for the breather from rad to header without problems either on road or on track days.

I wouldn't. I had some old coolant hoses that bulged dramatically when the engine was running. Shows how much pressure there is in the whole coolant system. The thought of one going pop (and the consequential rapid overheat and engine seizure) put me off using old hoses....

petrol pipe has always been dirt cheap when i've bought it

tom

wrapped silicone hose is ok but vacum hose has a tendancie to split under high preassure....