m42 radiator coolant bleeding woes - please help

[balooshinakus]

Alright guys, here's whats going on. I've been trying to bleed my s50 powered m42 radiator cooled car and am not having luck.

1.) Upper radiator hose gets hot, but the radiator and the lower radiator hose stay cool, this is with no fan of any sort running in my garage on a cool day (50s).
2.) No heat inside the car, the hoses are hooked up correctly with the spider hose going to the top, back of engine to the bottom.
3.) Temp sensor is not outputting the temp, it just reads at the bottom of the temp guage.

I have reverse filled the system by pouring coolant into the upper radiator hose and coolant comes out of the radiator when I do this. I have the car on an upward slope. I have revved up the engine with the bleeder open and the res cap off.

Where do I go from here? I am really confused as to why I get no heat inside the car and the radiator and lower hose stay cold. Is it a tstat problem? I would think that the fact that liquid comes through the top of the radiator when pouring down the upper radiator hose would eliminate this as a possibility but I'm not sure. I don't want to keep the car running all that long because I don't have a working temp sensor. I did use the e30 sensor but no luck on this.

Any help is REALLY appreciated, this is the last piece and then I can drive this thing to the exhaust shop, I leave for school Tuesday morning so I'm in a major time crunch.

[rThor432]

For some reason, my M42 radiator was a pain to bleed. I ended up warming the car up at first to the point where the t-stat should have been open while revving up and down to dis-lodge any stuck bubbles. Didnt open, so while the car was off I squeezed the top and bottom radiator hoses to basically hand-pump coolant through the system. I had a big bubble somewhere, and that did the trick to get it out. I also had a hole drilled in the t-stat to help with possible air pockets there.

I never have problems with any other cars bleeding out. For some reason that one wanted to be difficult.

[omar85]

same setup for me and same exact issues. i also have my aftermarket temp gauge on the lower radiator hose and it NEVER goes over 140. sucks.

[tonytony]

I didn't have a problem with my m42 radiator, weird. I did the usual turn the fan on full and and turned up the heat all the way, opened up the fill cap and opened up the bleeder screw on top of the radiator. After all the air bubbles disappeared i closed it and it was ready to roll.

which e30 temp sensor did you use? the blue one or the brown one? Your thermostat might be stuck open for some reason, did you replace it? Is there any pressure in the hoses at all?

[7pilot]

Remove the thermostat and drill a small hole in the radius to the inside of the O ring.
Make sure this hole is at 12 o clock in the housing.
start the engine and add coolant.
squeeze the lower rad hose 4-5 times a minute. Once the top hose gets too warm to touch, secure the fill cap on the radiator and loosen the bleed screw.whenn coolant starts to seep out, close the screw.
Imo, you want to palpate that lower hose in order to dislodge the airlock at the Thermostat.

m

[slow e30]

Remove the thermostat and drill a small hole in the radius to the inside of the O ring.
Make sure this hole is at 12 o clock in the housing.
start the engine and add coolant.
squeeze the lower rad hose 4-5 times a minute. Once the top hose gets too warm to touch, secure the fill cap on the radiator and loosen the bleed screw.whenn coolant starts to seep out, close the screw.
Imo, you want to palpate that lower hose in order to dislodge the airlock at the Thermostat.

m

why change what already works if you do it correctly?

it is rather simple.
1) warm up car
2) full blast heat
3) open cap AND loosen screw
4) wait for the fizz, bubbles, ect to stop. have extra water nearby to top off on the correct line once bled.
5) once bled, tighten both caps tightly.

Use a quarter for the bleeder screw. it will help out and not strip it.

Dont go drilling holes in the thermostat. if it was such a great idea, wouldnt it be part of the original design?

Make sure your correct sensor is in, working thermostat is in, if it is or isnt, and your not pleased with the temperature, switch it to something better.

i cant understand how people cant bleed one of the easiest radiators in a e30.

[rThor432]

^^You must be a mechanic.

[1990m3]

why change what already works if you do it correctly?

it is rather simple.
1) warm up car
2) full blast heat
3) open cap AND loosen screw
4) wait for the fizz, bubbles, ect to stop. have extra water nearby to top off on the correct line once bled.
5) once bled, tighten both caps tightly.

Use a quarter for the bleeder screw. it will help out and not strip it.

Dont go drilling holes in the thermostat. if it was such a great idea, wouldnt it be part of the original design?

Make sure your correct sensor is in, working thermostat is in, if it is or isnt, and your not pleased with the temperature, switch it to something better.

i cant understand how people cant bleed one of the easiest radiators in a e30.

Actually, it's is a PITA to bleed for some reason -- this coming from me who I consider an experienced wrench hand. If you search bimmerforums for e36 bleeding procedures, the same applies to the m42 radiator because of the built in coolant reservoir. It's not the same procedure for other e30's that have a separate, self bleeding reservoir.

I've bled mine 3 times. Twice it was a piece of cake, but one time I literally had to walk away for the day. Came back the next morning and got the air bubble out in 10 minutes and all was good.

[tonytony]

From reading all your replies, i guess i'm lucky i havne't had to deal with not being able to bleed the radiator

[Tchao]

Yea it was the same for me...just pop the bleeder screw, and let it bleed. As easy if not easier then the M20 late model system.

[318isbmw]

I put my front end up on blocks and turned the heater on full to get any air that's stuck in the heater setup out as well. Once we got the front end on blocks it put the radiator opening at the top so it bled quite easily. Before then, it was giving us hell. Another trick rather than drilling a hole is to put in a advil or whatever you choose in there to crack it open then it will dissolve as you go but will help out when bleeding.

[slow e30]

why does it have to be so difficult?

[MIKe30]

why does it have to be so difficult?

It's not. I feel like I've mastered it already **knock on wood**



I bled my s52 car with m42 radiator practically without even starting the motor!!


With brand new radiator and no coolant at all in block, this is what I did. Open bleeder valve and fill coolant till you cant fill anymore. You will hear a lot of hissing out of the screw. When it stops hissing and the coolant stops falling, close the screw. NOW BURP THE UPPER RADIATOR HOSE. Keep squeezing and letting go and squeezing and letting go. Bubbles keep coming back up through the expansion tank. Do it till your forearm hurts, then do it some more and more.

Then open bleeder screw and fill more coolant. When it stops lowering and hissing, close screw and burp the hose again. Keep burping. Keep burping. Keep burping.

Eventually you will feel the coolant coming through the hose your squeezing. Keep on burping till there are no more bubbles. Then open bleeder screw and top off coolant. Close screw. If no more bubbles show up after another few more tries burping it, you're good.


Then I started my car, turned on the heat full blast, the coolant will now circulate. Open the bleeder valve till only coolant comes out, and close it.

Now you're done.

[balooshinakus]

I ended up getting it bled. I think part of it was that I didn't let the car get hot enough, because I was nervous with not having a temp guage.

Temp guage was a wiring issue, the wire in the harness had been cut but the engines PO who had it swapped, not sure how it got cut but I resoddered it.

Got the system bled by leaving the car pointed up all night long to let air rise to the top, then I squeezed the top and bottom tubes a bunch and bled the normal way with res cap and bleeder out, let the car heat up a bunch with heat on and everything, radiator got nice and warm. I guess I underestimated how long it takes for the engine to warm up by a lot.

Thanks for all the responses though, hopefully this helps someone else.

[7pilot]

why change what already works if you do it correctly?

it is rather simple.
1) warm up car
2) full blast heat
3) open cap AND loosen screw
4) wait for the fizz, bubbles, ect to stop. have extra water nearby to top off on the correct line once bled.
5) once bled, tighten both caps tightly.

Use a quarter for the bleeder screw. it will help out and not strip it.

Dont go drilling holes in the thermostat. if it was such a great idea, wouldnt it be part of the original design?

Make sure your correct sensor is in, working thermostat is in, if it is or isnt, and your not pleased with the temperature, switch it to something better.

i cant understand how people cant bleed one of the easiest radiators in a e30.

Thanks for the dismissal.
thanks for your opinion.
This has worked for me for years on many different brands of car. Especially when that particular car is being troublesome
Allow me to offer suggestions to someone else while you restrain your attitude.
It also seems to have escaped your esteemed attention that quite a few thermostats DO have a bleed hole.
Good day to you sir.


m