Thermostat drilled holes

[moggy]

I need to replace the thermostat on the 325.

I was extremely lucky yesterday in racing. The radiator (e36) started leaking from the crimps 1 and the cap just before scrutineering. One hour later and a mad dash to qualifying, the car was running with the thermostat out (which had stuck open) and a templated cereal box as a replacement rubber seal.

I understand it is a good idea to drill a couple of holes through the thermostat to help with cooling issues and I wondered if there was any particular place that you should locate the holes?

[DanThe]

Drilling holes wont help cooling, it just means the engine takes longer to warm up, if you want the engine to run cooler then use a lower temp stat

[Mikey_Boy]

Absolutely agree with DanThe - you need a cooler stat!

Other things to look at if you are running hot - is your current radiator full of cr*p? This won't help. Are you getting enough air to the rad? Can air pass through the rad well enough (often overlooked?) Is the cooling system bled properly? Leaking rads won't help with cooling as it means the system isn't sealed so can't hold any pressure either. Plus of course, eventually you run out of water!

Cheers,
Mikey_Boy

[moggy]

Holes will help more when the car is stationary - this comes from a race mechanic who works on the best prepped e30 (non M3) I have seen. Additionally and independently another mechanic who races Formula Ford said exactly the same.

Anyway, where do I get a lower temp stat from?

[johnl320]

Not meaning to sound funny but if the 'race mechanic' told its a good idea to drill holes in the thermostat then why don't you ask him where to drill them?

[zaust]

That's just a quick fix as Dan said for idel temp's, Drill a 3mm hole or take the middle out, Not really a good idea in the long run. You say your cap was leaking. If the seal has gone in it then it may be a simple cap replacement that is needed. If it is letting to much pressure out, the system will boil and not circulate correctly.

[maxfield]

Only time I've ever seen a thermostat drilled is to ease bleeding up as M20's can be bastards.

[punko]

from personal experience from racing and using an e30 on the road id take the middle out of the stat so as you can remain using the rubber seal rather than the cereal box, you will find the bmw still reaches temperature without a stat unlike many four cylinder engines yet allows a lot better flow which is especially what you need with racing, i think your problem at cadwell was due to an air lock in your system not the thermostat because it was stuck OPEN!.
im mike by the way me and ash helped you yesterday.

[moggy]

Hi Mike

I'll be in touch with you chaps soon. Thank you for the help yesterday

Don't forget I'm on a straight 6

[moggy]

Not meaning to sound funny but if the 'race mechanic' told its a good idea to drill holes in the thermostat then why don't you ask him where to drill them?

Fair point. I don't use him (he has a handful of race cars he takes care of and doesn't have capacity for another), although I've received quite a bit of free advice. I don't want to push my luck with him.

Why have you put race mechanic in inverted commas by the way?

[Brian28]

As above, get rid of the whole centre bit of the stat and fit the outside bit with the rubber seal back into place again. Five seasons and at least half a dozen different cars, no issues at all.

[johnl320]

Not meaning to sound funny but if the 'race mechanic' told its a good idea to drill holes in the thermostat then why don't you ask him where to drill them?

Fair point. I don't use him (he has a handful of race cars he takes care of and doesn't have capacity for another), although I've received quite a bit of free advice. I don't want to push my luck with him.

Why have you put race mechanic in inverted commas by the way?

Dunno really, I suppose its a term that can refer to a formula 1 engineer or Dave down the Pub that had a Banger car team in the mid 70's. If you know what I mean.

[moggy]

As above, get rid of the whole centre bit of the stat and fit the outside bit with the rubber seal back into place again. Five seasons and at least half a dozen different cars, no issues at all.

:thumbup:

[E30_fred]

Drilled holes in a stats are a good idea, they allow the flow of some coolant even if the stat fails and sticks in the closed position. That flow of coolant can save your engine. I have never done it on a BMW but always drilled them out on tweaky minis and metros with the A series engine.

[nm1]

i drilled mine out i think its a good job as my stat jammed before and she pushed out all the coolant, i know it takes a little longer to get to operating temp, but i think its a good failsafe. my stat has been drilled for around 2 years with no sighns of any problems,