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Does anyone know the temp range of the temp gauge? I'm still having issues with operating temperature of my engine. It reads from 11:30-12:30, but it used to read a rock steady 10:30-11.

Temp at the radiator reads 170-180 does this correspond with the 11:30-12:30 position on the gauge???

It just feels like I'm still running too hot!!! I know 170 isn't that bad, but I always ran at 1/4 gauge until I swapped my sensors and thermostat, I have a completely new cooling system, and I KNOW my thermo is working after R&Ring it 5 times, and flushing the coolant 3 times.

I'm starting to suspect a blown headgasket but I have NO bubbles in the coolant, no water in the oil, and no apparent loss of cooling. Just hot running as per the gauge, hotter running when I use upper RPM, shit a/c (used to be 40 degrees F now is 75) and poor acceleration in upper RPM (which makes me think possible compression loss and uppper RPM due to blown gasket).

Any thoughts?????????????????????

I'm getting frustrated.

Rob

From what I've heard, BMW's are supposed to operate at the 12 o'clock position.

rob6118 wrote:Does anyone know the temp range of the temp gauge? I'm still having issues with operating temperature of my engine. It reads from 11:30-12:30, but it used to read a rock steady 10:30-11.
Rob

Rob,
Hope this helps, also check the G103 ground above the starter motor, which has been responsible for a couple of E28 temp gauge problems I've seen.
-Rod

I'm even more confused now. I was planning on taking the car for a 100 mile drive or so but turned back when I had it still running hot. I came home and R&R'd the thermo again and wrote the original post. Filled the reservoir up with antifreeze (pure) to balance out the water I filled up the system with last time. One thing I noticed is that when I rev the engine it emptied the reservoir.

This shouldn't happen right? This means the waterpump isn't getting suffecient liquid which would cause my overheating right?

Well I took it for the 100 mile drive to see if the latest R&R changed anything, or maybe if adding some extra antifreeze to the mix (I'm probably around a 30/70 antifreeze water mix) would help. The car still ran hot, especially anytime I got onto the gas until about 40 miles into the drive.

At 40 miles my a/c started working again and the heat all of a sudden stopped being an issue....

Now my temperature sits at about 10 o'clock while going down the highway w/o a/c, with a/c it sits at 11, and while idling with the a/c goes to 12.

The only thing I can think of is that I had a nasty air lock somewhere (despite bleeding the system at the fan temp switch, bleeder screw, and temp sending unit).

I still wonder about the temp range because if you are correct that means my sender is indicating 195 when my meat thermometer reads 175??? That doesn't make sense to me. I see a lot of aftermarket temp gauges that read from 100-280 with 170 being directly at 12 o'clock.

Either way I don't see how a ground point would cause a high reading. I could see a ground issue causing a low temp reading because then the voltage applied to the sender could never equal the reference voltage at the gauge.

I'm gonna add another half bottle of antifreeze and just keep an eye on it. Hopefully I don't have to remove the thermo for a sixth time.

Rob

Temperature at the radiator will never match the temperature at the sensor, since the sensor is seeing hot water from the motor. Top radiator hose is a better place to check engine temp if you're using an IR thermometer.

Jeremy

Excellent info, Rod. Thanks!

Rob, did you bleed the air from the coolant system after you opened up the W/P?

my temp gauge very rarely goes past 11 o'clock. if i leave it ilding for 10-15 minutes (which is never) i have seen it go almost to 12 o'clock. car is all stock and aux is unplugged currently.

At least you have a temp gauge that moves! Consider yourself fortunate!

Don't want Rod to think i wasn't grateful because I couldn't find that info anywhere elso........so thanks!

Tyler I know I know, lets just say I'm OCD and that's why I own an e28. It keeps me busy. Combine that with some bad experience with overheating aluminum engines and I'm paranoid.

Filmy, I assume you mean the water pump?? I replaced the water pump about a year ago and haven't opened it since. I've bled the system forever...................................multiple times at multiple places.

This is difficult to explain without an exact visualization of the housing but the housing is split into two sections. The back half of the housing allows coolant to flow out of the head into the upper radiator hose and with the thermostat closed there is no outlet for the fluid out of the radiator and therefore no fluid flows into.

The front half of the housing is cut off from the back half of the housing by a plate on the rear of the thermostat. With the back half cut off, the front half only allows fluid to flow through the thermostat into the water pump, through the block, out the head, into the back half of the housing and into the upper radiator hose.

So I believe the system works like the following. When the engine is cold the plate on the back of the thermo does not split the housing in half and therefore the waterpump can draw fluid from the back half of the housing (out of the head) but can not draw fluid from the radiator through the closed thermostat.

As the engine heats up however the thermo opens, and as it opens it closes off the joining hole in the housing, which splits the housing in half. This forces the water pump to draw all of its coolant from the radiator and forces all of the coolant being exuded from the head to be routed into the radiator hose.

The only thing I can think is that somehow the rear plate on the thermostat was sealing the housing off when it was cold. I mentioned above that when I hit the gas it sucked coolant out of the reservoir until I let off the gas and the coolant returned.

Really the only thing I did different on my drive was I cycled the heater valve a couple of times. I think one way or another the rear plate on the thermostat is now properly leaving the housing open and therefore the waterpump is getting proper flow. Also by splitting the housing off prematurely it would never allow hot coolant from the head to reach the thermostat directly and therefore cause it to open. This would therefore never allow the thermostat to open or provide any coolant flow to the water pump itself.

This would evidence itself in my symptoms of running very hot over all, only a modest improvement by driving at speed, and significant overheating when I hit the gas.

I believe by cycling my heater valve I allowed hot coolant to enter the front half of the housing (the heater core flows into the same line feed by your reservoir). This in turn provided the thermostat with its first priming of hot fluid which allowed it to cycle. By doing this a couple of times I allowed the thermostat to seat properly and function properly.

If anyone has any clarifications or modifications to my theory / experience speak up because I'll probably write another FAQ in a couple of days detailing my overall cooling system experience that way everyone has all this info in one spot instead of hunting through 10 pages of search results.

Rob

PS I also try to do a ghetto PSP drawing of some sort to illustrate my mildly confusing explanation above. Hopefully if you have a thermostat and housing in front of you you can understand what I'm talking about.

What you're experiencing is much like the problem "Derin" had with his 528i, as discussed here, which turned out to be a faulty new thermostat.
-Rod

I know, thermo was my first suspiscion (sorry for the spelling) so I order a new one from Steve, and that is why I refer to R&R my thermo 5 times, going back and forth between old and new (even though old has only 2 months of run time on it). I also tested both in water by progressively heating and measuring the temp at initial and full opening.

Thermo's aren't the issue I don't think, I think it is just the way the system is designed in our e28's. Every other cooling system I've worked on the thermostat points in the direction of coolant flow and therefore the back spring section sat in the thermo cover with the hose on it and there were no worries about a back plate sealing off sections or not sealing them off.

As per Steve, manual, realoem etc though I'm installing the thermo in the correct orientation and it only goes in one way Anyway.

Unfortunately I don't have an IR themp sensor but I am measuring at upper radiator hose on the radiator, as well as the coolant in the reservoir. It's not ideal but its the best I have.

I'm gonna cross my fingers and confirm that it is solved this morning on my way to work.

Rob

ITS FIXED!!!!!!!!!!!!!!!!

So I've finally fixed it, sorry for yelling but I've noticed everyone is doing it recently so I figured I'd join in. So what was it all along. Believe it or not just damn air in the system. I had bled the system at the bleed screw, housing plug in whole #5, temp sending unit, vacuum switch in housing, radiator fan temp switch, house to the reservoir etc etc e friggin tc.

I had just one trick left up my sleeve. I have had overheating issues in the past, on a Jeep Cherokee, and on that vehicle in order to fully bleed the system I just went through this cycle several times:

start engine
turn on heat
remove cap
fill reservoir
allow to warm up and over heat
turn off
allow to cool
repeat

Each time the engine would heat up it would push out some air and as it cooled down it would suck straight fluid as long as you kept the coolant filled. I did this 5 times this evening, giving the various hoses swedish massages while chanting haitian incantations and burning incense and human hair while the engine was running.

During the 5th running I finally got the temperature down to the 1/4-1/3 mark consistantly and it would creep up to 11:30-11:45 with the a/c on while idling in the lot. I closed everything up and proceeded on a 10 mile test drive. I absolutely flogged the damn thing and the hotest it would get was 12 o'clock with a/c on sitting at a red light after 3 miles of 0 to 60 runs spending the whole time over 4k RPM.

Now my needle stays at the 1/3 mark while idling with the a/c off as I'm used to, and goes to 1/4 while cruising w/o a/c.

I was surprised at how BMW ran the cooling hoses for this system. Apparently this setup is the difference between a self bleeding system like my old Jeep (1989 POS Pioneer) and my slightly older 1985 535i.

So for those of you who have a really frustrating experience with what seems to be a thermostat issue, test your damn thermostat once, put the bitch back in and trust that that isn't the issue and do a little hose massage.

After reading through 20 posts trying to troubleshoot this I'm going to try to use my experience replacing the entire cooling system to write another FAQ so that all the info is in one place.

What finally got me to sit down and really spend the time to try to bleed the system was I was left with either air in the system or a slightly blown head gasket. And given the choice of pulling the top half of the engine apart and spending several hundred dollars or making a couple of ritualistic sacrifices and you guys see which one I chose.

Have a great night, my e28 is back!

Rob

P.S. My slight power loss seems to now be cured as a result of a cooler running engine. Figures, too hot equals too rich which equals less power. Pulls smoother and harder now.