T-stat & control valve acting funky
 

Hi everyone,

So about 1.5 years ago I replaced the t-stat as part of the cooling system refresh (hoses, sensors, rad, ET, WP etc..) and it was working fine engine temp around 93C.

1. Recently i started to observe the k-temp (my android unit shows the coolant temp all the time) and noticed that the engine reaches the 93C fairly quickly and stays there between 91 - 96 driving locally. However on highway driving while accelerating it can drop as low as 81 degrees. before slowly climbing back up, given i keep thing constant. it does take some time to go back to 93 and if i speed up it can drop back quickly to 88, 84 etc..
this t-stat is almost new from FCP Euro: Mahle Behr 11537509227. could it have started sticking open?

2. on another note seems my amazon heater control value acts up from time to time (also replaced it about 1 year ago). where the driver sides starts to blow really hot air while passenger side is normal. connected a scan tool and while the value shows as closed, the heater exchange on left shows 88-90C and right side shows closer to what the set point is. I guess it sticks open, did anyone of you replace it with the non oem version, seems OE it pretty expensive at $180 or is that the only way to go? rockauto has the gates and other brands for around $100. the amazon one was $40 (didn't think much of it when i got it).

Note: the t-stat temps still act the same way even of the heater value is working normally. so i do not believe its related.

Any input would be highly apricated.

than you.

My rule for non OEM parts is when it's easy to access and not mission critical (you don't live where it's life threatening if heater valve breaks closed) and won't damage or prevent engine from operating it's fair game (bent my own rules a bit not realizing how hard it was to swap an aux fan geez BMW).


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The coolant temp dropping at times is a function of the DME controlled thermostat heater and is normal and the reason why the dash guage is programmed to stay in the middle over that range.

The reason for the non temp gauge on the dash pointing to noon from damaging levels of hot pot to damaging levels of cold is literally to prevent customers asking too many questions during warranty period. (as according to tech builtin). They don't think the average user can handle the truth (literally).

When the tstat fails open it will take longer to get up to temp and won't even reach temp when ambient is low.

Coolant temp should drop when you accelerate and warming element on thermostat is activated. But the basic temp seems a little low.

https://www.pss-autosoft.net/diagram...1214_M0KFK.htm

If your heater valve is stuck open you have an extra radiator running that is in the loop and cooling the engine even when tstat is closed. Logic dictates that will make the engine run a little cooler than the set point so your symptoms seem to match the conditions described.

You can use a hose pinch clamp to close off the heater core to confirm before you actually replace the heater valves.

I'll never refer to the dash-mounted temperature gauge again
 

The pointer of the coolant temperature gauge in the instrument cluster is located in the mid-position at coolant temperatures of 75oC - 113 o C in centre position.

I don't know much about the BMW M54 engine yet, but my experiences over 55 years with other

• 1) aluminum block/aluminum head engines,
• 2) iron block/aluminum head engines,
• 3) iron block/iron head engines

tell me that 113C (235.4F) is too high. I'd want the dash gauge to warn me about that temperature approaching, long before it was reached.

Operating temps, & over-temp and/or overheat experiences:
1) aluminum block & heads:

• a) '62 Olds F-85 with the 215c.i. V-8, that needed to be kept under 200F, or the head gaskets failed (2x),
• b) '08 Cobalt & '09 HHR with Ecotec all-aluminum engines, both run around 180F-217F (when the fan automatically kicks in)...the HHR experienced 245F, with no damage (1x, thru hose clamp failure), but never again, I hope.

2) iron block with aluminum heads:

• a) streetable engines always kept at gauge-displayed optimal running temps, no overheat experiences & no true temperatures known,
• b) race engine (427/441 c.i. 635 rwhp, was always temp-monitored and kept cooler than 200F, due to large alum. radiator, dual fans, separate transmission cooler/fan system, no T-stat (flow restrictor used instead), and a 55 gpm electric water pump. Goal was to run as cool as possible for higher horsepower, less chance of head gasket failure (14.1:1 compression ratio)

3) iron block with iron heads: the bulk of my experience comes with this combination. There were only two overheating instances overall, one survived it, the other engine didn't.

• a) '66 Chevelle had a mild 327-331c.i. (300hp) at first, and overheated badly (off scale), when its' first electric fan relay fried, far away from any parts store. I always carry a spare relay now, after electric fan conversions. I raced it later that day, and tore it down at home afterwards (decided to upgrade radiator, cam, lifters, manifold, carb), to check the head gaskets. They were OK. A survivor.
• b) '86 S-10 extended cab pickup, while driving to work, the temp gauge went off-scale suddenly in freeway traffic, and I pulled off the road. Don't know what happened, it was so sudden, but the head gaskets both failed, and I had the engine (2.8L V-6) replaced.

I've read a lot about BMW cooling problems, long before I ever thought of owning one. That's why I specifically asked my friend that acquired the X5 that he traded to me (for the '66 Chevelle drag-car) to be sure to repair/replace/restore the cooling system, which he did (except for the viscous clutch & fan, inexplicably). I observed much of his work being done....

Of course, I immediately put in a hi-power electric fan (3000 cfm), and thought it was good, until I was advised not to trust the BMW temp gauge. Since then, I've added an unused spare smartphone to my unused center ashtray, just to display the REAL coolant temperature at all times (via Torque Pro android app). I have it set to alarm me if I become distracted, and the temperature rises past 220F (104C). I figure that if my two Ecotec engines are Ok at, or below, that temperature, then my X5 should be OK too.

Run this hex code mod on your cluster. You need PA Soft 1.4 but my buffer is 10C.

https://xoutpost.com/1121333-post23.html

no laptop nor PA Soft 1.4 (yet)
 

Eventually, I'll get a cheap laptop with coding ability so I can get useful info on the display while driving. I'm not a programmer, but i'll give it a try. I already tried to use the BC programming trick, but it reverts back to ambient temperature.

So in the meantime, I'll use my Torque Pro App to monitor realtime coolant temps (I should've kept some gauges from my racecar!). Oil temp, oil pressure, transmission temp would be nice to have displayed as well. I can't find any BMW-specific PIDs to add to my TP app, either.

Torque or OBD Fusion work good to monitor temp. The moronic dial in the dash is literally pointless.

If the engine is too cold the heater stops working. By the time the dial moves to hot the steam coming from the hood is more apparent than the red light next to the useless dial.

I drove for months with my tstat not closing due to the idiotic programming of the non gauge only finding out why my fuel economy went to shit in July when October came around and my heater didn't warm the cabin.

There is no excuse for something to look like a gauge and not represent anything close to a temp gauge. It's a 3 position idiot indicator.

"Not warm"
"Possibly operating temp"
"Turn off engine immediately you have no coolant"