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My '79 528iA was running pretty warmly on the highway. It has a new thermostat, so I deduced it was the radiator. I had it re-cored and installed it this weekend. I filled it up with coolant, bled it and took it for a drive. The damn thing still runs hot! It's just below the 3/4 mark on the temp gauge.

Could it be that the thermostat is a faulty one? The lower radiator hose gets pretty damn hot - at least comparable to the upper hose. I don't know where else to look.

Maybe you installed the thermostat upside down? Easy to do. Or, yes, it could be faulty. At what temp. should it open when reached?
Did you bleed it through the small bleeder valve on top of the thermostat housing till nothing but antifreeze came out after a good warm-up with engine off?
Here's another trick; were the rear wheels sitting lower than the fronts while bleeding? Gravity brings the air to the top.

How stable is the gauge? If you see any movement when you use turn signals, heater blower, lights etc it's got a bad ground. Which will cause a higher gauge reading.

I used to drill a 3/16th hole in the thermostat to get the system fully bled out

If you want to try that.  


It also keeps the temp sensor at a more even reading which in turn improves the fuel injection.



On Mon, Aug 26, 2013 at 8:06 PM, GripGreg <gripgreg@yahoo.com (gripgreg@yahoo.com)> wrote:

Maybe you installed the thermostat upside down? Easy to do.
Did you bleed it through the small bleeder valve on top of the thermostat housing till nothing but antifreeze came out after a good warm-up with engine off?
Here's another trick; where the rear wheels sitting lower than the fronts while bleeding? Gravity brings the air to the top.



Rosallina/'80 528i
Country/'75 530i
Buster/'82 635Euro
'73 02 4 sale
Hit the apex

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Mike W. wrote:How stable is the gauge? If you see any movement when you use turn signals, heater blower, lights etc it's got a bad ground. Which will cause a higher gauge reading.

The temp gauge does move around quite a bit when I turn on other electrical items. I figured it was a bad ground, but I don't even know which ground to start with. Any tips?

Are you getting good pump circulation ? Check the reservoir for a strong current. Also the coolant -ways in the block tend to get crusty.....

JamusMcFamus wrote:

Mike W. wrote:How stable is the gauge? If you see any movement when you use turn signals, heater blower, lights etc it's got a bad ground. Which will cause a higher gauge reading.

The temp gauge does move around quite a bit when I turn on other electrical items. I figured it was a bad ground, but I don't even know which ground to start with. Any tips?

Start with adding a wire between the body and the engine. Medium heavy, like say #12 or so. Maybe from the strut tower nuts to the valve cover. But body to engine.

Thanks, Mike. I hadn't seen your reply until now.

Thanks, Mike. I hadn't seen your reply until now.

Replace the negative battery cable (has a ground strap under the fuse box). Worked wonders for me, and it's cheap and only takes 5 minutes to swap.