735i Overheating problem

Just purchased a used BMW 91 735i. Immediately changed the heater core
because of overheating problems. The car ran fine for almost exactly 1
week. Checked the coolant level and needed to add 1 gallon of
antifreeze after week 1. Six days later, the same thing. Eventually,
each time the car is running for period of time, coolant has to be
added. There are no visible leaks, no white smoke from the tailpipe.
The mechanic did not find any traces of oil in the coolant or
visa-versa. Both the radiator and the water pump seem to have been
changed in the last few years, but I have not been able to test either
of them to ensure that they are functioning properly. The clutch on the
fan does not move freely once it has heated up, so I assume that means
it is working as it should. I just changed the heater control valve
because it looked a little rusty. I am trying to check off all
possibilities before attempting a head gasket change. Can someone
please help? Perhaps the problem is right in front of my face and I
just don't see it???

BMW 1991 735i wrote:
> Just purchased a used BMW 91 735i. Immediately changed the heater core
> because of overheating problems. The car ran fine for almost exactly 1
> week. Checked the coolant level and needed to add 1 gallon of
> antifreeze after week 1. Six days later, the same thing. Eventually,
> each time the car is running for period of time, coolant has to be
> added. There are no visible leaks, no white smoke from the tailpipe.
> The mechanic did not find any traces of oil in the coolant or
> visa-versa. Both the radiator and the water pump seem to have been
> changed in the last few years, but I have not been able to test either
> of them to ensure that they are functioning properly. The clutch on the
> fan does not move freely once it has heated up, so I assume that means
> it is working as it should. I just changed the heater control valve
> because it looked a little rusty. I am trying to check off all
> possibilities before attempting a head gasket change. Can someone
> please help? Perhaps the problem is right in front of my face and I
> just don't see it???
>
That looks like the classic head gasket leak on these, my experience was
that the leak was pressurizing my cooling system and when the engine was
running the coolant hoses were much harder to squeeze than normal. Also
noticed the leaking cylinder had much cleaner spark plug than normal
ones and when I finally had the head done the piston heads on the
leaking cylinders were very clean...

I was thinking water injection might be a good way to keep things clean
inside

Good luck, Bob

go here... http://www.bimmer.info/forum/forumdisplay.php?f=10

it is the best forum for that engine, common problem they can easily help
you with

Bob, you're right about the spark plugs. So far at least one of them is
unmistakenly sqeaky clean. I took off the valve cover and I
disconnected the exhaust manifolds. I left the intake manifolds in
place as suggested on another website. As I unscrewed the 3rd set of
head bolts, I noticed that the oil on the screw was a bit milky
colored. I'm guessing that will be where I find the problem in the
gasket. I also found that one of the bolts was loose before I applied
any pressure to it. (wonder what problems that can cause?) Anyway, I've
loosened up the timing chain by removing the screw and spring that
causes the tension, however, I still don't have enough play in the
chain to pull it off the gear. ANY HELP, SUGGESTION, DIRECTION, on the
remaining steps of this teardown would be OH so GREATLY APPRECIATED!!
(On a tight budget, didn't have the $2,800 for the head gasket
replacement)

BMW 1991 735i wrote:
> Bob, you're right about the spark plugs. So far at least one of them is
> unmistakenly sqeaky clean. I took off the valve cover and I
> disconnected the exhaust manifolds. I left the intake manifolds in
> place as suggested on another website. As I unscrewed the 3rd set of
> head bolts, I noticed that the oil on the screw was a bit milky
> colored. I'm guessing that will be where I find the problem in the
> gasket. I also found that one of the bolts was loose before I applied
> any pressure to it. (wonder what problems that can cause?) Anyway, I've
> loosened up the timing chain by removing the screw and spring that
> causes the tension, however, I still don't have enough play in the
> chain to pull it off the gear. ANY HELP, SUGGESTION, DIRECTION, on the
> remaining steps of this teardown would be OH so GREATLY APPRECIATED!!
> (On a tight budget, didn't have the $2,800 for the head gasket
> replacement)
>

If you found loose head bolts, that may explain the cross contamination
and appearance of a leaky head gasket. Try just re-tightening the
head-bolts from scratch per normal torquing procedure. You may luck out.

--
-Fred W

BMW 1991 735i wrote:
> Bob, you're right about the spark plugs. So far at least one of them is
> unmistakenly sqeaky clean. I took off the valve cover and I
> disconnected the exhaust manifolds. I left the intake manifolds in
> place as suggested on another website. As I unscrewed the 3rd set of
> head bolts, I noticed that the oil on the screw was a bit milky
> colored. I'm guessing that will be where I find the problem in the
> gasket. I also found that one of the bolts was loose before I applied
> any pressure to it. (wonder what problems that can cause?) Anyway, I've
> loosened up the timing chain by removing the screw and spring that
> causes the tension, however, I still don't have enough play in the
> chain to pull it off the gear. ANY HELP, SUGGESTION, DIRECTION, on the
> remaining steps of this teardown would be OH so GREATLY APPRECIATED!!
> (On a tight budget, didn't have the $2,800 for the head gasket
> replacement)
>
Try this link:
http://www.bmwe34.net/e34main/mainte...gasket_M30.htm

Cheers, Bob

Anyone know how to set a BMW 735i at TDC? (top dead center). The
Bentley Manual does not explain how to do this...exactly.

On 26 Oct 2005 17:05:43 -0700, "BMW 1991 735i" >
wrote:

>Anyone know how to set a BMW 735i at TDC? (top dead center). The
>Bentley Manual does not explain how to do this...exactly.

Same as any engine. For any particular cylinder? You also may need
to decide between TDC on the compression or the exhaust stroke,
depending on what you are trying to achieve. You can do it either by
looking at which valves are open or closed, or, if you don't want to
take the valve covers off, then take out (probably) # 1 spark plug and
then the old method is to put your thumb over the plug hole to
determine when the piston is coming up on the compression stroke - or
the exhaust stroke - as the case may be. Then, you can use a pencil
or similar object to touch the piston top while you fiddle the
crankshaft back and forth to find TDC.

Perhaps I'm really just an old fart, and someone will tell me that if
you hook up a keyboard to the OBC and press ctl-alt-swastika with your
left foot down then the engine will do it for you itself.
--
Dan.

Thanks for the info. I used brute force and a pair of pliers to turn
the sprocket nut until I got it to TDC. I'm sure there is probably an
easier way, but I've played with this thing long enough. Time to move
on.

Fred,
Once I pulled the cylinder head off, the head gasket was in fact
cracked. I'm kinda glad that I did pull the head off. Now I know for
sure why the car is overheating.