Combustion gas in the cooling system?

[Dave M]

Please bear with my posts. I've been attempting to post the wloe thing at once, but the site seems to only allow small bits at a time for now, so here we go...

Ryan's thread regarding cooling system level/pressure below has made me think about the pressure in mine at operating temp.
As I reside in a rather rural, domestic pick-up (have one myself) type demographic area of Canada, I rarely see other e34s, let alone the M50 version, so haven't been able to check the pressure of another properly running example. I have been monitoring the coolant level but haven't yet determined if I'm going through a significant amount or its just differences in ambient temp at the time I'm recording.

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[Dave M]

What I'd like to know is;

How much pressure should the system have at operating temp (needle at mid point)? I don't have a pressure gauge, but cannot squeeze the upper rad hose together and make the two sides touch. Should this be the case. If the car is left to idle and reaches noon on the temp gauge, the upper rad hose remains relatively soft, once driven, its hard. Could this be gas breaching the head gasket or worse? I haven't tried to open the rad cap (cold) and have someone else drive slowly against resistance (ramp or block) to see if the level in the tank rises, but may try this if the responses suggest. There is no residual pressure in the system once cool and no oil visible in the coolant and vice-versa. Again, I had the head replaced 30,000km ago and shouldn't have this occurring unless the block is cracked. It will be going back to the indy if this is the case.

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[Dave M]

Since I love to post pictures and want to provide as much info as possible, here is an example of a plug pulled recently. Shown is the lighter side which I hope is not toasty coolant.




The other side is darker (oskar likes to help)



I'm off for the day to create another clearcut,

Thanks for any input,


Dave M

[GS535i]

Dave,
Looking into Oskar's eyes, I'm confident he wants to tell you " you only need fear fear itself". Dogs are often wiser than we! I don't think you have any problem from what you have observed.
Your plug looks a nice mid to light tan, which is fine. The hoses are normally 'hard' when the engine is at operating temp.
It's quite OK to open the expansion tank cap (rad cap) when cool - that's the only true way to monitor coolant level.
Were you getting exhaust gasses in the coolant jacket ( via a failing head gasket), coolant would most likely end up 'boiling' off, with a noticable level drop - which the expansion tank level alarm would signal.
BTW, if there is a problem which I didn't pick up on, I'll consult my German Wire Hair Pointers - they're better on BMWs and Porsches than my Irish Setter, and perhaps Chocolate Labs.

[Dave M]

I agree, chocolate labs are definitely more apt at serving as bear bait than BMW techs. Ask your Pointers about the 50-60mph shimmy, make them earn their kibble. Beautifull dogs BTW, Oskar spent plently of time as a pup learning the finer 'points' of dogdom from two of them.
Thanks for the peace of mind, other's posts can breed fear in my own mind. Just looking for a project I suppose, something simpler than a head gasket perhaps.

Thanks again,

Dave M

[ryan roopnarine]

to clarify, hopefully

somewhat squishable, but somewhat harder than other cars...ok
rock hard....get it checked out

I agree, chocolate labs are definitely more apt at serving as bear bait than BMW techs. Ask your Pointers about the 50-60mph shimmy, make them earn their kibble. Beautifull dogs BTW, Oskar spent plently of time as a pup learning the finer 'points' of dogdom from two of them.
Thanks for the peace of mind, other's posts can breed fear in my own mind. Just looking for a project I suppose, something simpler than a head gasket perhaps.

Thanks again,

Dave M

[Dave M]

Difficult to judge without a solid method, which I'm sure exists. I wish I knew what "rock hard" was and I know you know, as you've been through this before. Somewhat squishable is is, but still harder than your average VW or F250. I was a bike mechanic for 10 years while pursuing a racing career and got fairly adept at guessing tire pressures at various tire widths. I would guess the pressure in my top rad hose to be roundabout 25 psi.
As GS535 eluded to, I'm probably (hopefully) out to lunch and scared of nothing, we'll see in the future when I determine where, if at all, my coolant is very slowly disappearing to.

Dave M

[GS535i]

I agree, chocolate labs are definitely more apt at serving as bear bait than BMW techs. Ask your Pointers about the 50-60mph shimmy, make them earn their kibble. Beautifull dogs BTW, Oskar spent plently of time as a pup learning the finer 'points' of dogdom from two of them.
Thanks for the peace of mind, other's posts can breed fear in my own mind. Just looking for a project I suppose, something simpler than a head gasket perhaps.

Thanks again,

Dave M

With the skimpy data provided re the shimmey plus the ~485KKM on the car, the best I could get out of Jaxx (the better of the 2 pointers on Beemers) is that the thrust arm bushings may be soft - if so, the best replacements are the ones from the 750/850 (have these in my 535i)

[JR'Z 525]

Wow guys, I haven't thought about asking Buster the wonder mutt what he thinks about my Bimmers cooling system and spark plugs! He prefers the back of the Toyota P/U over the 525 though...
After these last several posts on this coolant loss thing, I think the bottom line is it might be normal for higher mileage M50's to loose a minute amount of coolant over over a certain period of time and/or miles. I think the key is we need to keep an close eye under the hood (which we all do) and determine what might be "normal" for each of our cars.
BTW, my 4 year old loved your dogs pics!
JR

[ryan roopnarine]

dave, after filling again, and bleeding, i went ahead and made some impromptu hose measures for you. although my cool system may not be the pinnacle of perfection, in light of the fact that it doesn't appear to be losing any coolant, i submit some data from a relatively healthy m50. at 12' temp needle position, 15-20 min drive, 6500 rpm kiss engine off, at straight section closest to upper radiator nipple, i was able to induce roughly 8/10 inch squeeze with thumb and forefinger (IE 4/10 inch movement for each finger). i'd tolerance my measures to 1/8 inch +/- (engineer ruler, oy, i know it doesn't make sense). if you have concerns, you could always make the shop you got it done at to produce another m50 for you to feel up hope this helps.