300d New thermostat, water pump = cold radiator and overheating
 

edit: 1987 300d
The only thing I can imagine is that the radiator is clogged. Also, from working on bimmers, I'm used to a coolant bleeder valve but I don't see one on this car (maybe i haven't looked hard enough). Is it possible that i have air in my system keeping coolant from flowing properly? If so, how do i get it out?

the metal hose above your thermostat that goes over to the expansion tank is the bleeder.
you could also have a stuck closed thermostat. did you test it? is is an O.E. stat or a "same as"?
call Roy at the "buy parts" button. he has a nice long list of updated thermostats for this car. get the latest and greatest.

Not to doubt you but did you get the orientation of the tstat correct?

My thought as well. Is the thermostat in backwards? Don't laugh (or ask) how I know it can be done......

It would be useful if you could tell us a little more.
When does the car overheat?
What is the condition of the coolant?
Have you done any recent work on the cooling system?

There are many good threads on cooling system problems, even diagrams on the correct installation of a thermostat.

Try this link http://www.dieselgiant.com/thermostatreplacementandmodif.htm

Yes it is an OE thermostat. I installed it with the longer, protruding portion facing the engine. I think that was the only way it would fit.

There's really not much to it. Once you start the car, the temperature increases when idling (faster when driving) and within a few minutes the temp needle creeps all the way up.

When I stop the car and open the hood the radiator is cold to the touch. The top hose is hot but not really too pressurized. The bottom hose is hot but squishy.

I was thinking a cracked head or gasket but i have no white smoke at all and there is no coolant in the oil.

it sounds like you did not get water into the block.
be sure and fill the head with the upper hose, and possibly disconnect the heater hose, and fill from there.
actually, I'm not familiar with the 603 yet. (I'm learning quickly) but be SURE water is exiting the small upper hose that connects to the expansion tank.

Thanks, I'll definitely take your advice. Has anyone had a radiator actually clog? I've read threads alluding to it but I've never experienced that in the past. I've only seen them leak.

oh sure. I've seen tons of clogged radiators.
morons that start out with a leak, fill with tap water, and keep filling and driving this way. rust, and lime from the tap water really does a number on aluminum and cast iron.
also letting the coolant expire and driving for years on old coolant will do the same thing.
I've seen shop rags in the radiator too... can't really blame the radiator on that one...

Ok, one more dumb question: What do you think of using CLR (calcium lime rust) to flush out the radiator? I think they sell it in walmart. If it doesn't hurt aluminum it seems like a win.

I'd only use the recommended citric flush myself. no.
and I'd only use it if the parts determined to have corrosion and damage. and I'd be prepared to replace the radiator if I had to use it.
pull the block plug, and see what comes out. look into the radiator and see if the tubes are plugged or corroded.
then flush normally, and see if the gunk and corrosion is still present. only then would I use the citric acid flush on this car.
also pull and inspect the water pump. the vanes could have been corroded out.

x2 on this.

You can make an acid flush using vinigar, citric flush, CLR, glacial acidic acid, anything I suppose if you understand pH and alkali metals (aluminum et al) but you will eat metal as you eat sediment, no way around it. If the metal is already thin (original with miles), it might make it too thin.

Antother thing that can clog radiators: mixing Dexcool with regular glycol-based coolant, or over-use of "stop-leak" products. Take both hoses off of the radiator, flush with water, if it comes out of the other end (bottom to top is best) then it's not clogged.

heh, keep the expansion tank cap on for this test...:rolleyes:

Ok, now I'm more confused.

I removed the radiator and flushed it well with the hose. Flow seemed normal, no chunks of anything, clear water coming out. looking inside through the neck, clean with no corrosion. I think it's safe to assume it is not blocked.

I fill up using the above method, filling through the top hose so the block is full (i assume), filling from the top neck of the radiator until full and then topping off the expansion tank.

After i hook it back up I took it for a ride only long enough for the temp gauge to go to the hash mark above 80. I pull over and feel around the radiator. The top hose is very hot as well as the radiator within a 6" radius of the top hose neck. The top hose seems under a lot of pressure and hard to the touch. The rest of the radiator is ice cold. The lower hose is cold and slightly less pressurized than the top.

Does the coolant flow bottom to top or top to bottom?