Any M50 thermostats lower than 88C?

[Peterlech]

My car runs just slightly past the center mark and is stable there with the 88C thermostat.

As I have a constant pinging issue in high ambient temperatures (on our 91 octane premium fuel) from 2000 - 2700 rpm under light load that several shops gave up on finding, I thought I would try a slightly lower temp thermostat. I heard that they are made, but cannot find one.

Originally the car ran slightly to the left of the center temp mark, but not with the last 2 thermostats. Water pump is new, car is well bled, front fan has been replaced, as low speed died; as I said, temps are stable there even in high ambients.

[shogun]

I would check the visco clutch.
http://www.mwrench.com/Whitepapers/FanClutchtest.pdf
11531721002 88 degree C
11531712043 92 degree C
75 degree ?

But that would then below the original operating temperature of the M50 engine. Older engines have the 75 degree t-stat.
The engine in your car runs best at a fairly high temperature. When the engine is cold, components wear out faster, and the engine is less efficient and emits more pollution. So another important job of the cooling system is to allow the engine to heat up as quickly as possible, and then to keep the engine at a constant temperature.
And this does not happen without T-stat.

The T-stat's job is to block the flow of coolant to the radiator until the engine has warmed up. When the engine is cold, no coolant flows through the radiator. Once the engine reaches its operating temperature, the thermostat opens. By letting the engine warm up as quickly as possible, the thermostat reduces engine wear, deposits and emissions.

The small cyle is within the engine only, large cycle means including radiator and heating system.

In my opinion it does not matter which T-stat you select, get the one which is best for the engine to work at it's designed temperature as soon as possible.
When it has reached the temperature the T-stat opens, and every T-stat opens then, no matter if it is designed for 70,80 or 90 degree Celsius. Open is open. And then the coolant runs thru the radiator.



Ping Preignition Fix
BMW E34 Ping Preignition



E34 M50 thermostat (75 vs 88 Celsius) experience
http://www.bimmernut.com/forum/5-ser...xperience.html

[Peterlech]

Thanks. Viscous clutch seems OK, car does not overheat even on hot day in traffic.

I am pretty sure it is carbon, as it is worse after a hot soak when parked for a short time, but several Techron treatments and some "Magic stuff" highly recommended by a reputable local Bimmer shop did not help. The Ping Preignition fix technique seems like it would be more effective - I read about this method years ago in my MG /Mini days.

The head was milled when it was rebuilt after a catastrophic radiator failure at 80K miles - the problem didn't get bad until maybe 35-40K miles after that, and we switched to premium fuel.

Ping Preignition Fix
BMW E34 Ping Preignition



E34 M50 thermostat (75 vs 88 Celsius) experience
http://www.bimmernut.com/forum/5-ser...xperience.html[/QUOTE]

[BennyM]

I don't think changing the T-stat will help anything either. I put the lower temp t-stat in my car, not because the car was overheating, but because it was cheaper at the time. I found that the engine took much longer to warm up in the winter months and the temp needle would actually drop if it idles too long on a cold (below 0F) day. Engine ran normally in the hot summer days. Even with AC on, the needle never went past the mid-point--though I remember reading that the needle is supposed to be a hair past the middle mark when the AC is on.

[Bill R.]

i would scan the car and check for knock sensor codes. bad knock sensors would allow pinging. And if they milled the head much and didn't use a thicker head gasket to compensate then your going to have pinging no matter what , the stock compression ratio for a m50 vanos b25 motor is 10.5 to 1, you're probably up over 11 to 1 now if it has the stock gasket thickness.

The stock head height on your motor is 140mm, the minimum thickness after machining is 139.7mm , you can only take off .3 mm or .012 thousands of an inch.

[Peterlech]

I don't think changing the T-stat will help anything either. I put the lower temp t-stat in my car, not because the car was overheating, but because it was cheaper at the time. I found that the engine took much longer to warm up in the winter months and the temp needle would actually drop if it idles too long on a cold (below 0F) day. Engine ran normally in the hot summer days. Even with AC on, the needle never went past the mid-point--though I remember reading that the needle is supposed to be a hair past the middle mark when the AC is on.

Thanks. I found out that the only lwoer temp thermostat available is 75C, too big a drop from the stock 88C.

My current idea is to decoke the head by using Seafoam in thru a vacuum line to remove carbon accumulation.

[632 Regal]

Clean it up and see if it helps. Did you pull the valve cover and look around in there? Check bolts, springs, rockers and cam wear.

[Tiger]

Bad crankshaft position sensor will allow the engine to run at abnormal timing curve. My friend has a 2004 Mercedes CL500 and it ran on the hot side... hotter than his other identical car... until he get the engine die when hot problem... After the crankshaft position sensor is changed the temperature drops to normal and car ran even more powerful.

Multiple possibilities... timing chain needs changing due to stretch... or even the fuel injector clogged or leaking.

[ss2115]

I'd like to relate an experience which although is not exactly the same, may relate.
My M50 vanos engine was losing water, and very slow to warm up, had high fuel consumption and pinged.
The head was removed and found a small crack into one of the clinders. It was easily welded and machined etc. At the same time the chap doing the job replaced the thermostat and its housing, and all the hydraulic lifters (192,500klms).
He found a lot of carbon buildup and cleaned as much as he could from the piston tops etc.
He also found the Vanos cam position sensor so carboned up that he was unable to avoid damaging it to remove it and so replaced it.

Engine back together and is silky smooth. The biggest difference is that its up to temparature (exactly midway on the guage) in about the first 3 minutes. No pinging and the engine now has that very distinct "on cam" feeling at around 4000rpm that i hadn't even realised was missing.
I mention all this also because my fuel consumption improved by 2 litres/100klms on the very first tankful.
Our conclusion for this was that it was coming up to correct temperature far quicker than the 10 - 15 minutes it used to take. Other engine parameters come into their own at the correct temperatures as well. One obvious item here is the O2 sensor comes out of open loop to closed loop operation.

So my advice would be to get the engine working at its designed temperature rather than trying to lower it.
Carbon build up, blocked radiator, viscous fan, electric fan - go over it all and get it right rather than looking for a bandaid solution that will only return a sluggish performing fuel guzzling car that won't be the pleasure to drive that BMW's can be.