Cooling system update

cracker red · 06-06-2009, 01:47 AM

I've been having overheat/hot running problems since I got this car running again.

95 M42 auto

Rad is new
Fan is working (actually stuck on the high setting...pulling the temp sensor plug does not shut it off - I havn't been able to figure out why this is happening, but it isn't causing the overheating either)
Thermo is new

Today I pulled the pump out....looked brand new. Impeller was in good shape, felt smooth when I turned it over, no play etc. This was a bummer, as I was hoping to find the impeller had self destructed.

ANYWAY....I removed the fan and felt the rad to make sure there wasn't any blockage....Nope...whole thing was HOT.

The upper rad hose was hot, but the lower one wasn't. That means (to me), that there isn't enough water flowing through the thermo....and why the car is running hot.

I removed the thermostat completely. Now the car runs dead in the middle of the temp gauge. I'm 100% sure I installed the thermo in the proper direction. I also checked the new AND old thermo on the stove....opened up at 189 deg. Just to double check, so I'm not an idiot....the thermo installs with the pointed end towards the front, and the spring sticking to the rear......I hope to god (or I'm a moron)

before the upper rad hose was hot and the lower was cold
now w/thermo removed, both hoses are hot, and the temp gauge runs dead-nuts in the middle

WTF over.

Flametail · 06-06-2009, 02:16 AM

I would assume that it is a thermo problem then. I had an issue with the cooling system back when I installed a new engine in my car. I had to go get my cooling system "burped" and everything worked fine.

Xenocide · 06-06-2009, 02:48 AM

yup sounds like its not properly bled.

MPWR · 06-06-2009, 02:50 AM

This is what the thermostat should look like under the cover.

If it looked like this before you installed the cover, you probably did it right. I doubt it would fit in backwards.

cracker red · 06-06-2009, 03:06 AM

Yup, thats how it was. Not sure how or what I'm doing wrong with bleeding it. Do you have to keep the reservoir full to the top while bleeding it?

I can re-install the thermo and try bleeding it again and again. I've done it 3-4 times and seem to get a few small bubbles but nothing substantial after the first time.

feeling the lower rad hose hot after I pulled the thermo I knew it would run fine (although take forever to heat up w/out thermostat).

If the temp goes above halfway, I've got to shut the car off and let it cool before trying to bleed it again? If so, why?

jono · 06-12-2009, 11:36 AM

it wont bleed when the cooling fluid is up to working temp you will just let the coolant out as a vapour under pressure .i dont think the m42 motor cooling system works proparly with the thermostat removed ,i would not drive the car with no thermostat under any circumstance

cracker red · 06-12-2009, 12:14 PM

How is bleeding it going to effect the thermostat opening up and circulating water? Because with the thermo installed the lower rad hose is COLD at all times.

Well, I might try re-installing it this weekend if I've got a chance. Seems to be fine, just takes a while to heat up

It's getting 27mpg without the thermo in and driving fine.

jono · 06-14-2009, 12:40 PM

i was told by a factory BMW tech that the engine wont cool proparly with no thermo i think from memery that most of the flow will be just through the radiator and not much coolant through the block have you tested the thermo in a jug of hot water to see that it opens correctly

Xenocide · 06-14-2009, 02:22 PM

Quote:

Originally Posted by jono

i was told by a factory BMW tech that the engine wont cool proparly with no thermo i think from memery that most of the flow will be just through the radiator and not much coolant through the block have you tested the thermo in a jug of hot water to see that it opens correctly

makes perfect sense, when the thermo opens the temperature wants to equalize in the system since there is such a huge difference. Without it the thermo opening is huge so most of the water goes out to the radiator

Flametail · 06-14-2009, 02:32 PM

Did you ever try replacing it and bleeding the system?

cracker red · 06-14-2009, 04:35 PM

Temp needle is fine, car is running fine no problems. I havn't had a chance to screw with it again, but might try tomorrow after work.

I tested the new and old thermostat, they both opened up in hot/boliing water (although not a lot of opening...maybe 1/2").

With the thermo installed, the lower rad how stays cold and the car overheats. With the thermo out, the lower hose gets hot (as it should...because its circulating coolant) and the car stays cool as it should.

I bled the thing until I'm blue in the face, so unless I'm bleeding it wrong, I dunno.

That whole remove the thermo and the car won't cool properly is an old wives tale. It was suggested that the coolant would pass through the rad too quickly for the rad to shed heat. It's a farse.

Xenocide · 06-14-2009, 05:08 PM

Quote:

Originally Posted by cracker red

Temp needle is fine, car is running fine no problems. I havn't had a chance to screw with it again, but might try tomorrow after work.

I tested the new and old thermostat, they both opened up in hot/boliing water (although not a lot of opening...maybe 1/2").

With the thermo installed, the lower rad how stays cold and the car overheats. With the thermo out, the lower hose gets hot (as it should...because its circulating coolant) and the car stays cool as it should.

I bled the thing until I'm blue in the face, so unless I'm bleeding it wrong, I dunno.

That whole remove the thermo and the car won't cool properly is an old wives tale. It was suggested that the coolant would pass through the rad too quickly for the rad to shed heat. It's a farse.

Glad you have a degree in thermodynamics. The engine can't maintain its happy temperature with no thermostat. You CAN cool it too much, IE highway with no thermostat. The engine will not be as efficient.

Thats like just running your AC full blast in your house, sure your not hot, but your not comfortable either.

tiFreak · 06-14-2009, 05:44 PM

if a car will run completely fine without a thermostat, why are car manufacturers putting thermostats in the cars? seems like a waste of money to me

maybe the new thermostat you got is defective, working as a mechanic I see this happen plenty of times, try getting another one

cracker red · 06-14-2009, 06:09 PM

I'm patching this thing up to use until I can find a motor swap for it. I may try another thermo, but I've wasted an entire day bleeding the damn thing to try and get it to work.

Perhaps someone has the proper procedure for bleeding the system they could post or link?

And no, no thermo degree here (but a few others). I'm not really concerened about it, although driving it in the winter wouldn't work (little to no heat). By the winter time I'll have found a motor swap and done it.

minicoop900 · 06-14-2009, 06:27 PM

may be the wrong degree thermo

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