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???
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BMW 1991 735i wrote:

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
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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)
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BMW 1991 735i wrote:

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

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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.
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BMW 1991 735i wrote:

That's good. If you had tried re-tightening the bolts you would have known soon enough since the symptoms would have remained. But you were able to short-cut that process.
--
-Fred W

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BMW 1991 735i wrote:

http://www.bmwe34.net/e34main/maintenance/engine/headgasket_M30.htm
Cheers, Bob
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Anyone know how to set a BMW 735i at TDC? (top dead center). The Bentley Manual does not explain how to do this...exactly.
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wrote:

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.

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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.
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go here... http://www.bimmer.info/forum/forumdisplay.php?f 
it is the best forum for that engine, common problem they can easily help you with
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