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Hi so my 320i is heating when I get on the freeway. lower speed through the City are fine it is overcooling though i'm a little lost as I pulled my thermostat to do a boil test and I've never had to deal with a t stat with so many ports can someone tell me how it flows I think my t stat is bad but not sure how exactly it is supposed to be working

Hi so my 320i having problems overheating but it only happens when under a heavy load or at freeway speeds but as soon as I let off the guess temp comes right back down can anybody tell me what I should be looking into. I'm not sure if that's a t stat issue water pump radiator etc that is the
Please if you have any input please feel free

First have a look here in the FAQ section for some direction: http://www.bmwe21.net/forum/viewtopic.php?f=38&t=13416

Read over them and went ahead and took my water pump apart thinking maybe that was it but my guess is the radiator

Since it's under heavy load or at freeway speeds, it is likely to be a flow problem indeed, water pumps are sensitive but could be a clogged radiator just as well. No coolant consumption or sludge in the oil system?

Yea I agree after looking at my radiator looks like somebody took jb weld to a few of the coolant fin things maybe that's why and as far as sludge goes there isn't any under the filler cap and I just changed the oil a few days ago

Hope a new rad solves it mate...

Put t stat in water and start heating, somwhere (80°C) before the water start boiling you should see inside the moving of t stat. and opening 2ports. You must see the diffrence before and after heating. But i don't think that your tstat is bad. becouse on city temp is ok. If tsta fail than also on city you will have heating problems.
I think your radiator is bad, i have same problem, when i drive on higher speed i have heating problem then i change the radiator becose he was worn... check condition of radiator (outside) if it
decayed. Mine old one I can scratch with fingers.

Merged topics, please keep things together in one thread, thanks.

It might be useful to check the vacuum tubes that are connected to the K-Jetronic system and the ignition timing. My 323I used to run slightly hot on the highway but was fine in Kuala Lumpur's heavy daily traffic. It never overheated though. My mechanic found a leaking vacuum tube. After this was sorted out, the temperature now sits in the middle of the gauge on the highway.

The average daily temperature in Malaysia is over 30C. So air-conditioning and proper engine cooling are essential. To help improve cooling, I use a triple core radiator made out of copper. It works extremely well especially in traffic.