Overheating

[~R~]

New to this forum.
I own a 1990 535i.
just recently it started overheating. I took out the thermostat and tested it and seems to be working fine. I noticed that the top hose coming from the thermostat turns hot when idling while the bottom hose going to the thermostat is cold as if there is no coolant flow. could my water pump be the reason? how can I tell if water pump has failed? there is no coolant leak that I can see.
any advice will be greatly appreciated.

 

[Big Daddy]

Is there air in the system? You may need to bleed the air out of the system using the bleed screw. Air in the system will cause an air bubble and stop the flow. And welcome to the fourm!

 

[~R~]

where would I bleed it for air?
and at what point do I know if the air is out?
thx

 

[Big Daddy]

Look for a screw on top of the thermostat housing or on the radiator itself. With the engine running and at operating temp slowly open the bleeder screw letting the air out. Once cooland starts flowing close the bleeder. See if this site helps"

BMW E34

 

[~R~]

thanks I will try that.
in the mean time how can I tell if my water pump is out?
is there a way to test or determine?
thanks for you reply.

 

[~R~]

I removed the thermostat and ran the car without it to see if the thermostat was causing the overheating and it turned out that the car still overheats and the hose that comes from the thermostat (top hose) to the radiator is hot but the one coming from the radiator back to the thermostat is cold (bottom hose) could it be the water pump?
any advise will be appreciated.
thanks ~R~

 

[Big Daddy]

With the engine off, grip the fan blades and wiggle them. If there is movement then the bearings in the pump are shot. If you run the car and no water moves then it would most likely be the pump.

Click the link I gave you, then click on "troubleshooting", then click on "overheating". This stie says you have the plastic impeller water pump and should replace it immediately. Read the info. there.

 

[~R~]

thanks I will check it out.

 

[~R~]

I went to the site that Big Daddy gave me but I didn't find much info on water pumps.
Big Daddy mentions that I have plastic impeller in my car, but I noticed that is for the e34 years '92 on. I have a 1990 does that mean I have the plastic impeller too?

 

[Big Daddy]

My mistake on the plastic impeller models not including the 90's model. I still think that the water pump may be the probelm if bleeding the system is not working and there seems to be no coolant flow.

 

[andreyiv]

Yeah, sounds like it. I had a similar problem, it continue to do everything even after taking out the thermostat, me being stupid enough, I didn't check anything and went ahead with a new pump. After taking the only one out, I realised it is good, well, too late now, the new goes in, with new thermostat and housing (old one was cracked a bit) still have the problem. Changed the fan (one blade was broken off) and fan clutch, bleed the system agian and no problems so far. Try bleeding the system really good and check the fan clutch although if you are saying there is no flow, the pump should be the problem.

 

[~R~]

would there be a coolant flow even if you had air trapped in the system?
or does air totally stop coolant from circulating?
by the way I installed a new fan clutch. the old one was in pretty bad condition. this was installed prior to having the overheating problem.
thanks for your replies.

 

[Puma]

One overheating solution - Rebuild

You can do what I did on 9/11/2004 when mine overheated. (noticed the date) I stopped my 1990 525i and looked under the hood. Saw some water had sprayed out of some part of the motor. I checked the water in the radiator. It was all good. I waited a period of time and decided to nurse it home. After I got it home it would not restart. The leak down test and compression tests indicated that I had melted the rings a 233,332 miles.

Now I am putting in a rebuilt motor out of Sacramento with a hotter cam and a polished head. It should arrive in a few weeks. I hope this will take care of my engine problems for the forseeable future.

Anyone - I am looking for exhaust headers for my 525i.

 

[digi]

I have the same model and the same problem bled system repeatedly, changed thermo, fan clutch, temp send unit, still overheating going to replace head gasket tomorrow. Will let you know if this works

 

[digi]

Bad news on mine turns out the gasket is fine but the head is cracked so looks like I will be replacing the head.

 

[~R~]

what about a clogged radiator, could that be the reason?
symptoms lean more towards that way in my car.

 

[digi]

A clogged radiator seems unlikely given what you have described, however flushing the radiator is inexpensive and will identify if this is the cause.