overheating engine after 15 minutes standing or driving

[slobman]

I have an 89 325i E30. I have replaced the radiator with a new one, replaced the fan clutch with a german model, replaced the thermostat with a german model, replaced the waterpump twice ( chinese first then german)Backflushed engine 10 times last time with all freeze plugs and engine block drain. replaced all heat related sensors. No discolered fluid when flushing engine only some rust flakes which drained through freeze plug openings. The hose that come from the thermostat side of the thermostat housing is hot but cold where the hose enters the lower radiator. I removed the thermostat completely but water does not seem to flow from the thermostat housing.All top hoses are blistering hot to the touch after 15minutes including the hoses that goe to the heater core which has been bypassed with a backflush coupler. The engine overheats with radiator fluid standing still or moving after 15 minutes period. Is the thermostat housing itself clogged? What the hell is going on.

[witeshark]

It seems that your thought that the flow is blocked makes sense.

[darkhorse737]

you didn't mention anything about bleeding the air... aka... purging air pocket/s out of the cooling system.

15min overheat is typical of an air pocket in the thermostat head-when steam accumulates there, it keeps the coolant from circulating properly; AND... temp guage climbs drastically because the temp sensor on the t-stat head takes up the temp of steam instead of the coolant temp.

[slobman]

Originally Posted by witeshark

It seems that your thought that the flow is blocked makes sense.

blocked from where . I'm baffled. do you think its the thermostat housing

[slobman]

Originally Posted by darkhorse737

you didn't mention anything about bleeding the air... aka... purging air pocket/s out of the cooling system.

15min overheat is typical of an air pocket in the thermostat head-when steam accumulates there, it keeps the coolant from circulating properly; AND... temp guage climbs drastically because the temp sensor on the t-stat head takes up the temp of steam instead of the coolant temp.

yeah I didn't mention that, but i did do that each time i refilled. it been opened so many time that now I can't completely close the bleed hole anymore. A small water bubble is always present by thebleed hole now, but it doesn't seem to be sucking in any air

[darkhorse737]

Don't fret, bro... sometimes you get lucky and purging the air is a single operation. Other times, it requires bleeding several times.

If u can see bubbles at the bleed screw, i suggest you replace it for a good fitting one. In the same way that a bubble indicates air coming out, it also means that it will let air into the system!

http://www.bimmerwerkz.com/forum/5-s...dle-57865.html

NOTE: the trick to purging air pockets in the link posted above.

Good Luck to you.

[slobman]

Originally Posted by darkhorse737

you didn't mention anything about bleeding the air... aka... purging air pocket/s out of the cooling system.

15min overheat is typical of an air pocket in the thermostat head-when steam accumulates there, it keeps the coolant from circulating properly; AND... temp guage climbs drastically because the temp sensor on the t-stat head takes up the temp of steam instead of the coolant temp.

So you don't think there is a problem with the thermostat housing being blocked?

After 15min and the engine overheats a lot of steam will exit from the bleed hole. Wouldn't there also be air present or is that just the water boiling out. I always fill the radiator with the bleed hole fully open until I see fluid coming out the bleed hole then I close, also I am doing this with the engine off. Should I idle engine while doing this. I also heard sbout having the radiator pressue filled, is there such a method or is it just a money making scheme for mechanics