92 BMW 325is Overheating

[rdbrock]

Hi,

I have a 325is that started overheating couple weeks ago, I did a radiator flush and drained it from the block plug as well, (because I didn't know how old the fluid was since I bought the car little over a month now) I put new fluid in there, I only used up about 1 gallon and a half, thought that was weird where there should have more fluid and it continued to overheat. I went ahead this afternoon flushed the fluid I added last week and drained it and replaced the Water Pump, Thermostat, Top and Bottom Radiator hoses, Clutch fan and new blade and put everything back together, and filled it back up only used the same amount of fluid as before about 1 1/2 gallon total (mixed 50/50 w/ distilled water) and I thought I had bleed the system correctly, I kept adding the fluid while the expansion tank plastic screw was out. I did not squeeze the hoses or turned the car on. I'm not too sure if I did indeed bleed it correctly, and maybe still have air in there and that may be a reason it still overheating? Does anyone know what else could be the problem?

Keep in mind I have no leaks, No cracks in the radiator, new thermostat and new water pump. What could be causing the overheat issue?

Thank you

[rdbrock]

Also the exhaust is not smoking at all seems to be running fine, except it over heats after 10 mins or so. is 1 1/2 gallon the normal amount that would take? I will check the oil next, but I don't suspect it's the head gasket. I'm thinking I may have air in the system? Are there any sensors that could trigger this overheating problem? I also have no heat, not sure why. The fan blows only cold air.
I also boiled the old thermostat and it did not open, So I was sure my issue was fixed, but this is not the case.

Thanks

[Manolito]

You are doing all the right things and you are running out of suspects.

Your cooling system holds 10 liters. That is just over 2 and 1/2 gallons. You never get all the liquid out, even when you drain the block, but 1 and 1/2 gallons seems pretty short for draining the block and radiator.

The fact that the heater does not work strongly suggests that there is still air in the system.

When you add water, are you getting water with no bubbles coming out of the bleed screw on top of the expansion tank? You have to fill the expansion tank clear to the top to get it to bleed. That means that the expansion tank will be completely full and it will push out a few ounces of coolant the first time the car warms up to operating temperature.

If your expansion tank is disintegrating inside (common problem) it will let air get back into the system within a few days after you bleed it, but the day you fill it up, the car should not overheat.

http://forums.pelicanparts.com/101-projects-discussion-forum-bmw-3-series-e30-e36-1982-2000/446171-bleeding-radiator-perhaps-problem.html

Have you noticed whether the electric fan is turning on? In reasonable weather, a car with a mechanical fan, or that is moving down the road, should not overheat even if the electrical fan does not work, but that is something else to check while the hood is up. If the fan is not working, the first suspect is the relay. Second suspect are the fuses.

I would suspect that the radiator might be clogged, and might not be draining completely for that reason, but I think that you found your main problem when the thermostat did not open, and now it is just a matter of getting all the air out of the system.

[rdbrock]

The expansion tank is solid, no cracks and I can still hear the air out when I open the screw some after I filled it up with coolant. I will try and re-bleed it , this time I'll have the engine running with cap open if there is no more fluid I'll drain some from the radiator and try to re-fill it to try this other bleed method. I agree with you that the heat should work as it's a mechanical heat ( even climate controls are twisting knobs). I agree with you it's probably going to be air, or fan relay. Do you know what this relay may be labeled as?

The fan works, it blows cold air, but if you are talking about the fan outside the ac condenser (fan outside that is closer to the radiator shroud )it only turns on when the AC turns on. As from what I understood and the radiator w/ fan clutch is what cools the radiator?

[Manolito]

When the expansion tank fails, you cannot see the problem from the outside (see the link in my last post.

You are correct that the mechanical fan should cool the radiator under normal conditions with no help from the electric fan, but

On my '97s there is a temperature switch on the passenger side end of the radiator. It turns the fan on low speed at one temperature and on high speed at a higher temperature. If you unplug that sensor and jumper its plug with a paper clip, you should be able to get high and low fan speeds if the key is on. If you hear the relay click but the fan does not turn on, the likely problem is that the contacts are burned out of the relay (common). If you touch the relays while someone clicks them, it is easy to tell which relay it is. If the relays don't click, check the fuses.

You should not need to start the car to bleed the system, and I think that you will find that doing so is a little messy. The water tends to surge a lot when the engine is running if there is air in the system. The heater valve should be open when bleeding the system.

[bostogrun]

Have you pressured checked the cooling system?

You replaced a lot of stuff maybe something is not seated right like waterpump o ring.

Is the radiator (expansion tank pressure cap) in good order; does it have all it's o rings. Sometimes the pressure cap looses it's multiple o rings and the cap doesnt hold pressure. The lack of cooling system pressure doesnt cause problems at start up but it does cause a problem when the car heats up.

[rdbrock]

Good news is that over-heating issue seems to be solved, it is running normal temps now and no longer overheating( it had a little bit of air inside the cooling system ), I did not let over heat much but apparently that cheap plastic radiator hose tip cracked.( was not the original issue, but another issue I ran into) I could still make grip with the hose, but it will need a radiator for sure and very soon, but the only issue left I cannot seem to pin-point at this moment is the heater that is only blowing cold air. I was sure once I had replaced the thermostat,water pump the heat would come back.