5-Series (E12,E28, E34, E39, E60)Chat relating to the BMW 5-Series of all generations. Specific models include: BMW 518, BMW 520, BMW 520i, BMW 530i, BMW 528i, BMW 530i, BMW 518i, BMW 524d, BMW 525i, BMW 525e, BMW 528e, BMW 540i, BMW 535i, BMW 520d, BMW 525td, BMW 525d, BMW 530d, BMW 525i/xi, BMW 530i/xi. (BMW 5-Series Forum)
Hello, I am new here. Recently purchased the above mentioned car and have had some overheating issues. Basically the coolant is not circulating through the engine because the lower radiator hose never warms and the upper radiator hose is always warm/hot depending on the temp of the engine.
I r2 the thermostat and bled the system. For 3 months this seemed to correct the problem. However, I just had another overheating episode. I check the reservoir and noticed that the fluid was low, although there isn't a visible leak. I am assuming that the water pump is acting up therefore pressure builds up in the radiator and spews overboard (that is why I lose fluid... maybe)
Can someone let me know if they have experienced this problem. I refilled and bled the system again and so far so good.... but the lower hose is still cold and not heating up. Thanks!
I believe that the lower hose should be cool....someone correct me if I am wrong, but the upper hose is the return hose FROM then engine and the lower hose feeds the engine with coolant....the one that feeds the engine should be cooler as it is sending coolant to the engine that has already travelled through the radiator and the heat has been exchanged. It sounds more like there could be an issue with coolant circulating to the engine....have you checked that the water pump is funcitoning appropriately
did you get a BMW thermostat? I put a Stant in mine and it did the same thing, the Import parts guy said you dont get good results with them and suggested the OEM part number. Also you have to bleed the coolant system a LOT before its right. And there is a sequence to do it in.
Had similar overheating problem with my '97 528i:
1)Started getting hot at idle, traffic lights etc - diagnosis: new fan hub - $180
2)OK for a few weeks, started getting hot at idle again- everything checked again, cracked head-$3600 for re-manufactured head (fitted)
3)OK for one week then temp gauge started going to 3/4 mark for a minute or so before returning to normal- new thermostat, by this stage no $ -going onto a bill
4)Temp gauge still moving at random engine speeds; back into shop- diagnosis low speed auxiliary fan not working and I suggest faulty coolant temp sender- possibility but never heard of before.
5)Engine temp taken with external laser gauge with car gauge showing hot-74 deg celsius rising to 100- normal temps.
6)Fitted after-market digital temp unit reading head temps Maximum temp reached 86 deg celsius
7)New Dual temp sensor fitted (in side of head under inlet manifold) and new low speed resistor pack in aux fan- all problems solved after 6 months.
8)The next thing we would have looked at would have been the-in dash gauge itself
9)if anyone is interested in the digital unit I installed simply google "engine watchdog TM2"
it's available here in Australia, but they will send it any where in the world, even reading in deg F
AN EXTREMELY SENSIBLE AND USEFUL BIT OF EQUIPMENT AS IT IS EQUIPPED WITH A SETTABLE ALARM THAT GOES OFF AT HIGH TEMP.
Last edited by tezza07; 04-03-2009 at 09:31 PM.
Reason: left out some vital info
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