Downsides to running without thermostat?

[LTDScott]

Next month I will be racing my '87 325e in a 24 Hours of LeMons race at Buttonwillow raceway. Simply put, this means 13-14 hours of racing at 100+ degree temps. Keeping the car cool is a priority.

Some racing veterans have suggested removing or at least gutting the thermostat to remove a potential failure point. Preferably I'd remove the center section of the t-stat so the outer "ring" will still act as a somewhat of a restrictor, or I could replace it with a piece of sheet metal with a hole in the middle.

I obviously realize that removing the t-stat means the engine will take longer to warm up, but given the conditions I don't think getting the engine up to temp will be a problem. But are there any downsides of doing this that I may not be aware of? Are there any other cooling tricks you can share?

FYI the water pump/hoses/belt are new as of last year, radiator (early single row) seems to be in good shape, and the mechanical fan has been removed and replaced with an electric pusher on the front of the rad. We must run ONLY WATER in the system per LeMons rules. The car has never run hot during our previous races, but they have been in much cooler weather conditions.

[smooth]

The problem is that if the car can't get up to temp you'll be running rich with poor combustion. You might think that racing around will get your engine up to temp, but if your cooling system is too efficient and the coolant is flowing freely from the get go it might stay too cool.

The thermostats are supposed to fail in the open position anyway, so assuming that holds true there isn't any benefit to removing a t-stat. Replacing it with a piece of sheet metal with a hole in it sounds like backwards logic to me.

Who are these racing "veterans"? Are they BMW drivers? I grew up in San Diego before I moved to OC and as a matter of routine maintenance we would yank t-stats from our MOPAR V8's.

On my BMW, though, I make it a point to actively filter out any old-timer "backyard" domestics mechanic advise because it doesn't translate very well to European engineering in my experience.

[LTDScott]

No, not BMW drivers, just racers in general, which is why I'm questioning their knowledge :)

[jlevie]

The engine will be slow to come up to temperature, but in +80F ambients you'll be fine with no thermostat.

I wouldn't worry about coolant temps if the cooling system is clean, the thermostat is working normally, and your electric fan moves enough air to cool the system during a double yellow or red flag condition. A 16" fan rated for at least 1800cfm is necessary.

My Spec E30 is used for Enduros (90 minutes to 3 hours) and we've never had any cooling issue in temps up to 100F. I have a 16" 1800cfm pusher fan, 80C thermostat, and 82C fan thermo switch (backed up by a manual override). The temp gauge will settle just a bit past half way during a double yellow or red flag event due to stored heat, but the fan will bring it down to just below half way if racing doesn't soon resume.

[LTDScott]

Thanks again jlevie for the personal insight. Maybe I'm being paranoid, but I know that lots of other cars fail out of the race due to overheating. I'm confident that our cooling system (including fan) is in good shape and works well, but the racing conditions we'll be facing are about as strenuous on a cooling system as you can get.

[smooth]

I'm pretty sure he'll be racing in 100+ ambient temps :(
I wouldn't drive north of LA during the summer by choice!

No, not BMW drivers, just racers in general, which is why I'm questioning their knowledge :)

It's not their knowledge I'd be worried about so much as whether their hints/tricks/shortcuts/etc. is applicable to our vehicles. I've not found much of anything I learned growing up to be of much use and often does more harm than good :)

My suggestion is to get some BMW racers' opinions and just smile and nod politely when non-BMW drivers offer their "advice"

[jlevie]

Thanks again jlevie for the personal insight. Maybe I'm being paranoid, but I know that lots of other cars fail out of the race due to overheating. I'm confident that our cooling system (including fan) is in good shape and works well, but the racing conditions we'll be facing are about as strenuous on a cooling system as you can get.

Remember, these are $500 clunkers. The ones that I've had personal knowledge of started the race with questionable cooling systems, at best. So it was no surprise for those cars to have a cooling system failure during the event.

You want new hoses, new water pump, new thermostat new belt, a known good radiator, adequate fan cooling and a clean (as in chemically flushed) cooling system. Unless the engine is running lean it won't overheat or otherwise have a cooling system problem. It is also important, in the case of BMW, to know that there isn't a small head gasket leak as a result of past overheats.

[LTDScott]

This is our 3rd race and all of the above items have been replaced (except the radiator, but its been flushed), so I hope we're good.

I think I may replace the t-stat with a failsafe unit though.

[LTDScott]

jlevie, I just wanted to let you know that I ran the stock thermostat and the rest of the cooling system exactly as specified at the beginning of this thread and the car ran cool as a cucumber for the whole race (at 95*+ temps). Thanks for the advice!