another overheating thread

**BMWe36AS** · 11-28-2016, 11:00 PM

So about 3 weeks ago i was sitting in traffic cool calm and collective, then something told me to look down and when i did i saw that the oem temp gauge was slowly creeping past half. Thinking to myself wtf is going on. Immediately i hit my manual fan switch turning on the mishimoto fan from inside the cabin and after a few seconds it began to come back down. clearly my fan was not coming on to cool it down. Now i have no idea what happened but it has been fine for just over a year now. and i'm really stuck.

My car has the 91/99 fan switch,and a mishimoto electric fan wired in with a manual "on" switch inside the cabin, for those lapping days.

SO i can turn my fan on manually and i know its on but for some reason it will not turn on at the temp's its supposed to.

wiring is as follows blk/bl and bl from aux fan switch are connected to + on the mishimoto fan. and the brown to the ground on the mishimoto fan.

now before anyone says to verify where its connected to. i have had it wired the way it is for over a year now, not once have i had an issue, it came on normally and at temp when it was supposed to. even at countless lapping days the oem temp gauge never went past half. just all of a sudden the fan doesn't want to turn on.

i originally thought my actual fan switch at the rad was faulty, so i changed it for a brand new one and still nothing. i have no idea what to do next

also after this i did install an AEM coolant gauge into the car, with the temp sendor being located directly at the head. i get 219-222 def F on the gauge and that's about when the the oem gauge starts to creep over to the right.

any help is appreciated!

**samy01** · 11-28-2016, 11:11 PM

i dont know how you hooked up your switch. but aren't there two relais which are for the fan, in the fuse box ? maybe check these.

**BMWe36AS** · 11-28-2016, 11:16 PM

the switch is like this:

switch + is connected to the black/grey at the temp sensor in the rad
switch - is grounded

the switch controls the ground at the temp sensor

**Eric93se** · 11-28-2016, 11:46 PM

Manually start the fan by using a fine strand of copper. Unplug the temp switch and jumper the center to one of the sides, try both those are the two fan speeds. If they don't run, then check the fuses, then check the relays, lastly the fan could be bad.

**BMWe36AS** · 11-28-2016, 11:51 PM

i tried jumping the pins at the fan switch, both speeds work. fan turns on. switch is good. fan is good

**Eric93se** · 11-29-2016, 12:29 AM

How old is your pump? Maybe it's failing when hot, slipping on shaft.

**LockDots** · 11-29-2016, 06:12 AM

I'm guessing your E-fan is wired to come on along with the Aux fan? If so, then if the aux fan comes on when you jump the pins at the fan switch in the radiator but it doesn't come on during normal operation perhaps your fan switch isn't getting up to temperature. I've seen this happen when there's a pocket of air in the radiator not allowing the fan switch to come up to the temperature of the coolant. Use an infrared thermometer to check the temperature of the body of the fan switch. It'll run lower than it actually is due to heat dissipation but it'll give you a good idea when compared to the body of the radiator (assuming you have an aluminum radiator) or hose.

I had a similar issue on my car originally where the relays tested ok (tested them externally) and the fan turned on when powered directly at the relay socket (via a power probe) but wouldn't work under normal conditions. Turned out to be some corrosion built up on the relay terminals. Took some contact cleaner and light brushing to them and they were back to normal.

**Eric93se** · 11-29-2016, 01:43 PM

He already explained, his mishimoto is 100% manual, he has a switch INSIDE the car.

**LockDots** · 11-29-2016, 02:39 PM

Originally Posted by Eric93se

He already explained, his mishimoto is 100% manual, he has a switch INSIDE the car.

That's not how I understood it. I took it to mean that he has a manual turn on for it in addition to the triggering from the fan switch. See quote below.

Originally Posted by BMWe36AS

SO i can turn my fan on manually and i know its on but for some reason it will not turn on at the temp's its supposed to.

**Turbohugh** · 11-29-2016, 03:21 PM

You can always put the OEM setup back ..

**Eric93se** · 11-29-2016, 05:13 PM

Your right Lockdots, my bad.

So he doesn't have anything stock for cooling, just the mishimoto, both positive outputs that normally feed the stock aux fan are sent to the positive of the mish fan, the black is grounded. Maybe check the grounding, could be corroded.

**BMWe36AS** · 11-29-2016, 06:31 PM

Originally Posted by Eric93se

How old is your pump? Maybe it's failing when hot, slipping on shaft.

waterpump and thermostat are 2 years old in january.

Originally Posted by LockDots

I'm guessing your E-fan is wired to come on along with the Aux fan? If so, then if the aux fan comes on when you jump the pins at the fan switch in the radiator but it doesn't come on during normal operation perhaps your fan switch isn't getting up to temperature. I've seen this happen when there's a pocket of air in the radiator not allowing the fan switch to come up to the temperature of the coolant. Use an infrared thermometer to check the temperature of the body of the fan switch. It'll run lower than it actually is due to heat dissipation but it'll give you a good idea when compared to the body of the radiator (assuming you have an aluminum radiator) or hose.

I had a similar issue on my car originally where the relays tested ok (tested them externally) and the fan turned on when powered directly at the relay socket (via a power probe) but wouldn't work under normal conditions. Turned out to be some corrosion built up on the relay terminals. Took some contact cleaner and light brushing to them and they were back to normal.

correct the e-fan is wired in so all oem functions are the same. when car is at temp, when ac is on and my own manual control. i will have a peek at the above mentioned and see what i can come up with. initially i thought maybe an air pocket, but my level of coolant hasn't gone up or down in the last year. this all just happened all of a sudden. i will also have a look at the relay's, any idea where they are and which ones they are?

Originally Posted by Eric93se

He already explained, his mishimoto is 100% manual, he has a switch INSIDE the car.

the mishimoto is wired in so all oem functions still worked fine as its my daily car. the manual switch inside the car serves as a back-up or whatever yo uwould call it so i can turn it on as

i please after lapping sessions.

Originally Posted by Eric93se

Your right Lockdots, my bad.

So he doesn't have anything stock for cooling, just the mishimoto, both positive outputs that normally feed the stock aux fan are sent to the positive of the mish fan, the black is grounded. Maybe check the grounding, could be corroded.

i will have a look at the ground as well but it doesn't seem likely. to my understanding if i can jump the fan at the fan switch pin connector i would assume the ground over there is fine. it's just for some reason once the car reaches temperature the fan does not turn on

after discussing this with a friend i will also be checkign to see if my tstat is operating as it should. its possible that the tstat has low flow and isn't passing the coolant through correctly. i didn't even thin kthat my 2 year old tstat could be an issue already.

**Eric93se** · 11-29-2016, 08:46 PM

yes a stuck/failed thermostat would explain the cause, however all the thermostats are failsafe. Do you have a link to the exact one in your car? You can remove it and test it in boiling water, unless the temp is over 100C which it shouldn't be.

**LockDots** · 11-30-2016, 07:36 AM

Just so you don't have to remove the tstat and re-bleed the system, test the fan switch first.

If jumping the pins at the fan switch get the e-fan to come on then the relays, terminals, and wiring between all of these components is fine. I suspect something with the fan switch, whether it's the fan switch itself or something not allowing it to come up to temp, such as a bubble.

You can remove the fan switch and either hook it up to a meter or leave it connected but probe the wires with a meter to see if ground is switched to the low/high speed pins when it comes up to temperature. You can try either putting it in hot water or heating it carefully with a heat gun.

You mentioned no low level of coolant, but remember that a very slow leak won't be apparent right away. Even something as simple as a cracked bleeder screw can allow a bit of air in the system keeping the fan switch from coming in contact with coolant 100% of the time.

**BMWe36AS** · 11-30-2016, 07:43 PM

Originally Posted by Eric93se

yes a stuck/failed thermostat would explain the cause, however all the thermostats are failsafe. Do you have a link to the exact one in your car? You can remove it and test it in boiling water, unless the temp is over 100C which it shouldn't be.

confirmed it is not the tstat today

Originally Posted by LockDots

Just so you don't have to remove the tstat and re-bleed the system, test the fan switch first.

If jumping the pins at the fan switch get the e-fan to come on then the relays, terminals, and wiring between all of these components is fine. I suspect something with the fan switch, whether it's the fan switch itself or something not allowing it to come up to temp, such as a bubble.

You can remove the fan switch and either hook it up to a meter or leave it connected but probe the wires with a meter to see if ground is switched to the low/high speed pins when it comes up to temperature. You can try either putting it in hot water or heating it carefully with a heat gun.

You mentioned no low level of coolant, but remember that a very slow leak won't be apparent right away. Even something as simple as a cracked bleeder screw can allow a bit of air in the system keeping the fan switch from coming in contact with coolant 100% of the time.

i went ahead and checked everything today.

fan still can be jumped at connector, relay's are all good, i have no fuses blown. fan electrical system good.
checked that both ends of the coolant hose on the rad are both insanely hot once warmed up. check, so tstat is good
i raised the front end in the air, and ran the car to hopefully rid the system of any bubbles, had zero bubbles come out just straight coolant so this tells me there is no air in the system.

i did notice that i can touch the fan switch without getting burned tho, not exactly sure what that means i thought it would be getting just as hot as the hoses?

back to having no having no idea of whats going on? what are the chances that the brand new fan switch is also dead in the water?

**LockDots** · 11-30-2016, 07:45 PM

Originally Posted by BMWe36AS

confirmed it is not the tstat today

i went ahead and checked everything today.

fan still can be jumped at connector, relay's are all good, i have no fuses blown. fan electrical system good.
checked that both ends of the coolant hose on the rad are both insanely hot once warmed up. check, so tstat is good
i raised the front end in the air, and ran the car to hopefully rid the system of any bubbles, had zero bubbles come out just straight coolant so this tells me there is no air in the system.

i did notice that i can touch the fan switch without getting burned tho, not exactly sure what that means i thought it would be getting just as hot as the hoses?

back to having no having no idea of whats going on? what are the chances that the brand new fan switch is also dead in the water?

.
Not likely, but not impossible. And the fan switch should be getting hot to the point where you can't hold it.

**Eric93se** · 11-30-2016, 08:33 PM

Well one 'mod' that I've mentioned a few times is to insulate the fan switch. I've tested my 80//88 fan temp switch and found the 80 was triggering more at ~102 or something (its been a while). That temp was measured in the rad near the switch with a probe. So I thought that sucked real bad. I then wrapped the sensor with rag and the fan came on real close to the set temp. The more permanent fix is to wrap the switch with an insulator, I used Styrofoam. Problem solved.

**LockDots** · 11-30-2016, 08:47 PM

Originally Posted by Eric93se

Well one 'mod' that I've mentioned a few times is to insulate the fan switch. I've tested my 80//88 fan temp switch and found the 80 was triggering more at ~102 or something (its been a while). That temp was measured in the rad near the switch with a probe. So I thought that sucked real bad. I then wrapped the sensor with rag and the fan came on real close to the set temp. The more permanent fix is to wrap the switch with an insulator, I used Styrofoam. Problem solved.

.
I was thinking about doing something similar. I'm thinking of using something like fiberglass copper pipe insulation - the kind you see used in homes. If I wrap the inside and outside of it in metal ducting tape it should insulate pretty well and keep heat contained within the switch.

Do you also have an Aluminum radiator? I'm thinking that some of the fan switch's heat dissipation has to do with this. The factory radiator has a plastic tank that it screws into (which I find to be a good insulator). The Aluminum radiator acts as a giant ....well....heat radiator, or dissipator. I believe this takes away some of the heat that would normally be constrained within the plastic tank walls. This is heat that would normally be transferred to metal - in this case, the fan switch body/probe. By insulating the fan switch you're keeping whatever heat the fan switch body is conducting from escaping, in turn raising it's temperature.

I'm not a physicist or well versed in thermodynamics so this is a guess at best.

**Eric93se** · 11-30-2016, 09:15 PM

That's true, I do have an all alum rad. I have my old original one, I'm going to take a look at the old design.

Yup fiberglass insulation will work great. Just don't let it get wet, you can wrap. Yeah, I just looked it up and it's not going to work well with water spray, unless you can seal off the fiberglass with duct tape. I have my styrofoam held with duct tape, very tight.

**BMWe36AS** · 11-30-2016, 09:22 PM

Originally Posted by LockDots

.
Not likely, but not impossible. And the fan switch should be getting hot to the point where you can't hold it.

hmmm i can definitely hold onto it with my bare hand no problem

Originally Posted by Eric93se

Well one 'mod' that I've mentioned a few times is to insulate the fan switch. I've tested my 80//88 fan temp switch and found the 80 was triggering more at ~102 or something (its been a while). That temp was measured in the rad near the switch with a probe. So I thought that sucked real bad. I then wrapped the sensor with rag and the fan came on real close to the set temp. The more permanent fix is to wrap the switch with an insulator, I used Styrofoam. Problem solved.

i might have to give this a go, whats the worst thats going to happen, i still wont have my fan come on at temp? haha

edit*: for the record i do not have an full aluminum rad its the stock one with plastic end tanks

**LockDots** · 11-30-2016, 09:37 PM

It should definitely get to the point where you can't hold it then. I remember my fan switch would get that hot with my original radiator and with my aluminum radiator it still got hot enough to where I knew it would hurt if I kept my hand on it too long.

Try a new expansion tank cap or bleed screw to make sure you're not sucking air into the system. You may be pulling air in and letting it out as the system pressure increases and decreases during use creating a temporary bubble.

**BMWe36AS** · 11-30-2016, 10:07 PM

Originally Posted by LockDots

It should definitely get to the point where you can't hold it then. I remember my fan switch would get that hot with my original radiator and with my aluminum radiator it still got hot enough to where I knew it would hurt if I kept my hand on it too long.

Try a new expansion tank cap or bleed screw to make sure you're not sucking air into the system. You may be pulling air in and letting it out as the system pressure increases and decreases during use creating a temporary bubble.

i have the new mishimoto expansion tank which i think i got at the beginning of the season

**shogun** · 11-30-2016, 10:41 PM

Originally Posted by BMWe36AS

waterpump and thermostat are 2 years old in january.

Age of the water pump does not matter, we just had an overheating case in the E32 forum , water pump 1 year old, and in the end the water pump was the problem http://www.bimmerforums.com/forum/sh...oblem-with-E32

back to normal... all problem was from water pump no working anymore even its replaced 1 year ago but mostly not original part. now i bought GK and looks good part.

**BMWe36AS** · 02-21-2017, 07:58 PM

i would like to bump my thread as my problem still exists. It's hard to judge how its all going with the cold weather, but we have had some goodluck weather wise here and its been warm for a few weeks now. so i can see the fan still does not want to turn on by itself at the desired temps.

I have had the temp sensor at the rad wrapped in a 1" piece of styrofoam this entire time, still no change back to square 1.

As for shoguns comment about the waterpump, i assume it is OK as both the lower and upper hoses are scortching hot, its gotta mean theres flow of fluids? am i wrong?

i just don't know the next move.

side note, what are expected temps AT THE HEAD once the engine has been running for a while and nice and warm.

-198-201 on highway cruise speed (120kph), no traffic
-210 will show standing still for a while (the temps creep up slowly, winter temps it doesn't shoot up as fast) At 210 i freak and hit the manual override so I can enable the fan myself
-219+ is the needle starts to move past 12o'clock

what does all this mean in relation to the temp at the rad, where the fan switch is supposed to trip and turn the fan on? I would imagine it should be tripping on the low setting somewhere by the 201 temps?

**Richard81** · 02-21-2017, 08:37 PM

I have not read this thread so sorry if this has been covered. The stock E36 two speed auxiliary fan can be tested as follows :

http://www.nmia.com/~dgnrg/page_20.htm

And the double temp switch can be tested by mildly overheating the engine (3 needles width to the right of optemp, which is 12 oclock on the gauge) by blocking the radiator and grills with a large board and running the engine at idle. Once it reaches that test temp, shut the engine down, then immediately key2 the ignition. Goto the front of the car and you should be able to hear the fan running at high speed. After some time, it should switch down to low speed, and then switch off a short while later.