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      01-31-2013, 11:47 AM   #23
Major General

Drives: BMW F11 535i Touring
Join Date: Mar 2007
Location: Scotland, Highland Region

iTrader: (0)

Originally Posted by superflyguy9 View Post
So I am screwed then - as it sounds like this is the only thing left to do?

One chap mentioned the "Top Hose Thermostat Modification" in a previous post and that worked successfully- as I undertand this is inserting a "Thermostat" into the top hose preventing any Bi-pass situations. I searched and searched for this but couldnt find the spec or DIY on how to do this and with what parts - or is it safe to do versus the "costly" gearbox heat exchanger repair?

Is there anything else I can do / try to diagnose my low coolant temperatures Definitively??

Thanks again for your help
Not so sure about a top hose 'in-line' thermostat. I know the Rover 75 guys do so with the BMW engine, but they don't have EGR thermostats, so a little less coolant complexity. But there is a delay in how an external thermostat responds, all depends on how big the bleed hole is and as soon as it is big enough, there is also a leakage of heat again. I'm not sure I'd want any delays in coolant performance, particularly on hot days, or when having a DPF regeneration.

Plus you really want the main thermostat working properly anyway, it's of the by-pass type (has a by-pass plate fitted). So when fully open under hot conditions, the plate valve closes off the reduced flow by-pass circuit and ensures the coolant circuit changes to full radiator flow.

The real issue is in checking the oil cooler thermostat. You'd need to clamp the hose that loops it to the radiator. Difficult to get at, but as it also shorts across the controlled by-pass coolant circuit, introducing cold coolant, it will cause very slow warm up and prevent optimum ECT.