Overheating M42

[750]

My radiator had a crack in it at the top so figured I would just go in and replace most everything. Part 2 on this, after I bought the car have only put a few miles on the car and of that 99% freeway from where I bought it to my place.

Replaced
-Radiator
-all belts
-thermostat
-water pump
-pulled mechanical fan, put in an electric.
did not replace the hoses, looked really good.

Filled and bleed test drive, over heat. Refill, bleed again test drive over heat. Just in case the thermostat was a bad unit, pulled it re filled bleed test drive and over heat. Found where some one had jacked up the front end of the car and did that fill and bleed, over heat did this 3 times in the outside hope the next time it would me magic. Made sure all belts where to the right tension re fill bleed, test drive overheat.

The only time it did not over heat was when I left off the radiator cap on a test drive.

Just to be sure my head gasket was good, did a compression test on each cylinder. All were in range, the outside ones though were a little high.

Any ideas?

[Vivek]

The only time it did not over heat was when I left off the radiator cap on a test drive.

I'm not sure, but this seems to suggest that there may still be some air in the system. That's the only reason I can think of that leaving the cap off would help.

What's your process for filling/bleeding it? I always just fill it to Kalt, rev the engine a bit til some bubbles come out, fill more coolant, and repeat until there are no more bubbles. I've never had an issue.

[Massimo]

Turn heater on.

Open bleed screw.

Fill Radiator.

Then keep topping up and reving the shit out of her for about 5 mins. Then close the bleed screw once most of the air bubbles are gone. BTW try to close the bleed screw while reving the car this will prevent it sucking air back in.

Oh and is it over heating while stationary or while driving?

[750]

Turn heater on.

Open bleed screw.

Fill Radiator.

Then keep topping up and reving the shit out of her for about 5 mins. Then close the bleed screw once most of the air bubbles are gone. BTW try to close the bleed screw while reving the car this will prevent it sucking air back in.

Oh and is it over heating while stationary or while driving?

Forgot to add, I did have the heater turned on, one of the things in looking for a reason for overheating to try.

When it was just sitting with the motor running the heat only went to the 1/4 mark. It only over heated on my test drive.

I will try revving, though it is going to be Tu before I have time again.
thanks.

[750]

Update
This might help some one else who is having the same problem. Failed this test.



So now down to if I want to pull the head or try some fix it head gasket sealer.

[bmwman91]

Pull the head. That fix-a-leak crap will cause you far more problems than it will solve.

[unevolved]

Pull the head. That fix-a-leak crap will cause you far more problems than it will solve.

Agreed. Do it right or don't do it at all. Half-assing will get you nowhere.

Sent from my PC36100 using Tapatalk 2

[Dj Buttchug]

im calling bullshit on a blown head gasket. 1st off. those stupid chemical tests often give you shitty results.

Before you tear into this thing let the car sit overnight with the bleed screw open and the cap off. next day go out top it off and drive. if it still overheats then consider a hg.

Also feel the radiator hoses. If the lower side is cool and the upper side is hot, you know right then and there youve got a big bubble and no coolant is flowing.

[750]

After 3 gallons of antifreeze and 6 gallons of distilled water. Trying every way possible of getting out any and all air. We just left off the cap. (and just for the record I did not want to believe the test was right) With the cap off and the accelerator pressed, air just came bubbling out. Lots of air. No water in the oil, so going with the bad head gasket, perhaps even warped head.

To late on the tear into it part. I am in M42 hell. I spent the better part of way to long on trying to get the manifold off. I put it back together and it sounds like crap. Found this link http://tis.spaghetticoder.org/ helped a lot, but I am still missing something. Waiting on a DVD that is about M42 rebuilds to come in.

[Dj Buttchug]

damn sorry to hear that. good news is the job is not that hard. Look through my build thread. You will find detailed pictures of a hg job I had to do. It should help.

best of luck

http://www.r3vlimited.com/board/showthread.php?t=188951

[irish44j]

agree....HG isn't that hard (though when I did mine the engine was not in the car). Take the IM off.

ziptie your timing chain to the sprockets before removing from the timing sprockets, so your timing will stay set correctly.

Pull head.

Clean surface

New HG

Replace head

New head bolts.....torque per instructions in the FSM/bentley.

Put everything else back together.

It takes a while, but it isn't terribly difficult in a technical sense.

[unevolved]

Throw some ARP head studs in there that aren't torque-to-yield and do your future self a favor.

[750]

Woooohoooo! finally got this thing put back together. Learning curve. Before this it was old tractors and Chevy.
Now that I have the new head gasket in, can burn rubber with out it over heating.(head gasket kit from NAPA came with new head bolts) On a side note, left off the preheating tubing that was around the throttle body. Why heat the throttle body in the first place?

Thanks for the tips. Used the zip tie one.

Replaced the steering rack while I was in the middle of all of this. Rack Doctor got me the replacement in and core deposit back in no time.

After thanksgiving when I can get it inspected will post up a photo of the under the hood. (Can't work on the car where I live so garage a hour away drive)

[bmwman91]

Glad to hear that you got it sorted out!