90° thermostat for N62 engine

[arktis 59]

I've read a bit about lowering the opening temperature of the thermostat on N62 to keep it cooler.

You can get it to NZ for less than $200 from Turner:
https://www.turnermotorsport.com/p-637061-performance-thermostat-90c/

This has been discussed in significant details on international forums, but I'm interested to know what you guys reckon.

This seems like a smart move to me, but then there's the thought that BMW had their reasons for choosing the factory opening temp. Did they do it because it's best for the engine, or because it's best for emissions? My understanding is that cars are most ecologically friendly when running hot.

What effects would you expect from this change/upgrade? Has anyone tried it?

[Allanw 1072]

The hotter the engine runs, the more power it makes (to a point!) for the amount of fuel going in.

The hotter the engine is, the less heat energy it can absorb from the combustion... so it helps economy by a tiny amount, and reduces emissions by a tiny amount.

I changed our E39 525i (M54) to a fixed temp stat and did away with the Map-cooling. E39's didn't bring up a check engine light for no map-cooling, but did have a fault code (Which was dumb, because when the thermostat heater burnt out, they just ran really hot ALL the time!). The 6's didn't run *that* hot on the mechanical only anyway (98?), like the V8's did (108?).

I didn't notice anything dramatic change as far as economy, but you want to make sure the new stat stays 100% closed until the engine is at operating temps, or it'll take longer to heat up and use way more fuel during the cold start enrichment phase.

My first kit had a bleed hole drilled in the thermostat and it was stupid and unnecessary. I replaced it with a solid one and it was way better.

Later cars may be a bit more complicated, but that unit looks like it still has a map-cooling heater anyway?

[GorGasm 563]

If it ain't broke...

[Allanw 1072]

... it soon will be???

[arktis 59]

On 2/2/2024 at 12:48 PM, Allanw said:

The hotter the engine runs, the more power it makes (to a point!) for the amount of fuel going in.

The hotter the engine is, the less heat energy it can absorb from the combustion... so it helps economy by a tiny amount, and reduces emissions by a tiny amount.

I changed our E39 525i (M54) to a fixed temp stat and did away with the Map-cooling. E39's didn't bring up a check engine light for no map-cooling, but did have a fault code (Which was dumb, because when the thermostat heater burnt out, they just ran really hot ALL the time!). The 6's didn't run *that* hot on the mechanical only anyway (98?), like the V8's did (108?).

I didn't notice anything dramatic change as far as economy, but you want to make sure the new stat stays 100% closed until the engine is at operating temps, or it'll take longer to heat up and use way more fuel during the cold start enrichment phase.

My first kit had a bleed hole drilled in the thermostat and it was stupid and unnecessary. I replaced it with a solid one and it was way better.

Later cars may be a bit more complicated, but that unit looks like it still has a map-cooling heater anyway?

I hadn't heard of map-cooling, so I had a read here:
https://www.meeknet.co.uk/e38/E38_Map_Thermostat.pdf

Voltage is applied to the thermostat itself if the DME detects a temp overrun (113° in his example). A thermostat with a lower opening temp should still open long before this point.

The dilemma is warmup fuel economy vs. cooling system lifespan. On the N62 there's a really horrible-looking job involving the coolant transfer pipe that I'd like to avoid at all costs..

[Spinner99 55]

I thought this video gave a really good explanation of the coolant temperature range for a MAP thermostat relative to engine load and speed. Even if you just watch the first 2-3 mins that should give you a good overview.  TL;DR = sometimes the car will open the thermostat at 85 degrees ish, sometimes it'll let the car warm up over 100 degrees.
 

 

On 2/8/2024 at 10:10 AM, E63 said:

On the N62 there's a really horrible-looking job involving the coolant transfer pipe that I'd like to avoid at all costs..

I didn't think it looked *that* bad? I will add I'm making the assumption that you'd be doing what I'd do and use the AGA Coolant Pipe https://agatools.com/products/n62-n62tu-coolant-pipe ?   I agree the factory one (that needs the front bumper & radiators etc  removed to insert it) doesn't look fun at all   .  There's also a work around option that's easy to install called the "Bimmerfix" stent  https://bimmerfix.com
 

Just adding a quick edit - the "Uro" coolant pipe option I wouldn't consider, it looks like it'd give up at the time least convenient to you..

 

Edited February 13 by Spinner99

[Olaf 3341]

In my humble opinion - and the experience of having run an N62 for 7 years and 36k kms with uncompromising maintenance, it's a non-issue.

My personal view re the coolant pipe 'issue' is that it's caused by neglect. If you do a coolant flush annually (instead of the recommended bi-annually), with BMW Blue coolant, the likelihood of failure is greatly reduced.

Perhaps the higher temp contributes to cooking/hardening the valve stem seals?  Mine were replaced, I did oil and filter more frequently than BMW and the condition-based servicing in the iDrive calls for.

There's enough to do on an N62 to keep it running reliably and well, without looking for modifications.  All those seals and gaskets to keep oil on the insides (and the outsides dry and clean), including the upper and lower oil pan gaskets.  PCV bellows. Valve cover gaskets.  Cooling System services.  Replacing the intake actuator as they fail causing low RPM minor roughness and bad fuel economy.  The list goes on, coils and plugs, then there's the Auto to service, all the suspension and brakes. 

I was never concerned about the engine 'running hot'', the design is for efficiency.  My e30 - by contrast - takes way longer to warm up.

HTH.