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Discussion Starter · #1 ·
Ok I know overheating is a big issue with the 2003, 3series 325I, and have read it all.
I have replaced,
radiator and expansion tank,
water pump,
the lower hose with the Coolant sensor,
the thermostat,
radiator cap,
new fan clutch and fan
I have ordered all new O-rings for the hoses.


Issues I have solved is,
the coolant temp sensor when O-ring gets old will let coolant steam out around the O-ring.
also the same issue occurs with all the O-rings with in the coolant system.

I do believe there's a better way to bleed the system that the dealer has to use for this car if not all. I bled it very well and actually gotten pretty good at it.

my issue is,
When it over heat's, I can gun the engine and the temp will drop.
I know right? thermostat or system not bled well enough. I got that

I discovered that the electric fan comes on for a split sec and stops is that normal? shouldn't it run for a while before turning off?
I disconnected the water temp sensor and the electric motor comes on and runs wide open.
-So I left the temp sensor unplugged and the fan running wide open I went down the road and it over heated within 2 or 3 tenths of a mile and I couldn't gun it to make it drop. Is there an issue I'm not aware of with the electric fan and does the water temp sensor control some thing else?

- Also when running hot when I turned the heater defrost on to help cool it, it dropped the temp rapidly, but it would not control it after awhile I still have to gun it to get it to cool enough to get it home.

I admit that a water flow issue is occurring or air is getting in the system,
after I get all the o-rings replaced I will re-bleed and test it again, but do you see any other issue that may be occurring from your experience???

issues could be
1-air in system or not bled?
2-new Thermostat bad?
3-restriction in the system. Could it be the new radiator?
4-o-rings?
5- electric fan?
6- leak in manifold?

Thanks!
 

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ROLL TIDE!
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You didn't say how you need the system, but it sounds like you know how to do it. Maybe let us know what you do.

Did you use the proper amount of coolant and distilled water? I've seen guys fill them too full of tap water and have the issue you describe. You want to fill it 50-50 with BMW coolant and distilled water only.

I have seen bad tstats out of the box, it sort of sounds like that is your issue. What brand parts did you buy?
 

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By looking at the list of things you have replaced and the problem is still there I would say youre in the same troube as me right now - blown head gasket or possibly crack. I came to this forum to look for help and what I see is that youre having very similar problems. And I refused for a very long time to believe that this is head gasket or a crack because the problem was not progressing at all. Everyone will tell you that when head gasket goes it goes pretty fast, in a matter of days it from innocent overheating it will start blowing your cooling system apart. But its wrong. I drove my car for about two years for sure since it started to do various tricks with cooling system, slowly but constantly loosing coolant, pressure too high in cooling system, once blew the radiator reservoir which got replaced and I was driving for more than a year with nothing blowing up. A couple hoses blew off and I just reclamped them. I only started to suspect the head gasket (or crack) when my car was starting to get misfires after parked for longer time (minimum 3 days) but that was not happening always, very rarely. But now until two days ago I realized that it happens now even every morning. And started to smell steam that smells much like coolant coming from the exhaust pipe. So today I decided to remove spark plugs and see how they look like. And one of them was coming out very hard. I had to fiddle and screw it back and forth until it came out - you dont want to apply too much force as those threads are in aluminum and its very easy to ruin them. Long story short - that plug was all covered with residue from burnt coolant and it was firmly sitting in threads at the very tip of the plug. Next thing I did - just wrapped/rolled a piece of paper towel into a long tube that would fit into spark plug and dipped it into cylinder. When I pulled it out the very tip of the paper towel was wet - and yes, it was the coolant. So.. You probably should not wait too much and pull the plugs, see if any is coming out with lots of resistance and then dip something into that cylinder. Do this after the car has warmed up completely so there is high pressure in the cooling system that will then leak into cylinder. Let it cool a bit so you can work and remove plugs and do the check.

And there are none of the usual suspects in my case - the cooland is clean, there is no foam in oil, the car basically does not even overheat. So I was thinking no it cant be head gasket. Or a crack. I should have done this check earlier. Now I will have lots of buildup in that cylinder because it was burning tiny amounts of coolant possibly for years.
 

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Discussion Starter · #4 ·
You didn't say how you need the system, but it sounds like you know how to do it. Maybe let us know what you do.

Did you use the proper amount of coolant and distilled water? I've seen guys fill them too full of tap water and have the issue you describe. You want to fill it 50-50 with BMW coolant and distilled water only.

I have seen bad tstats out of the box, it sort of sounds like that is your issue. What brand parts did you buy?
We have a good sloping area to get the front end up and turn the key on with out cranking the car and turn the heater on up to 91 and blower to low. Remove bleeder scew and fill the resivore until the fluid is coming out of the bleeder screw hole and poor slowly while are comes out and stop then place screw back in. I found now to leave the radiators cap off crank the engine, turn blower to hug and let air keep coming out with bleeder open as well. I found the air come see out a lot faster. After its to hot place ap back on and continue to bleed it until clean fluid is streaming. Also yes use 50/50 coolant and distill water. I use the bleeder to get the coolant level right, but let it cool and more than likely it will need a little coolant o jus right. I got most parts from oreily's which most are actually oem...
 

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Discussion Starter · #5 · (Edited)
By looking at the list of things you have replaced and the problem is still there I would say youre in the same troube as me right now - blown head gasket or possibly crack. I came to this forum to look for help and what I see is that youre having very similar problems. And I refused for a very long time to believe that this is head gasket or a crack because the problem was not progressing at all. Everyone will tell you that when head gasket goes it goes pretty fast, in a matter of days it from innocent overheating it will start blowing your cooling system apart. But its wrong. I drove my car for about two years for sure since it started to do various tricks with cooling system, slowly but constantly loosing coolant, pressure too high in cooling system, once blew the radiator reservoir which got replaced and I was driving for more than a year with nothing blowing up. A couple hoses blew off and I just reclamped them. I only started to suspect the head gasket (or crack) when my car was starting to get misfires after parked for longer time (minimum 3 days) but that was not happening always, very rarely. But now until two days ago I realized that it happens now even every morning. And started to smell steam that smells much like coolant coming from the exhaust pipe. So today I decided to remove spark plugs and see how they look like. And one of them was coming out very hard. I had to fiddle and screw it back and forth until it came out - you dont want to apply too much force as those threads are in aluminum and its very easy to ruin them. Long story short - that plug was all covered with residue from burnt coolant and it was firmly sitting in threads at the very tip of the plug. Next thing I did - just wrapped/rolled a piece of paper towel into a long tube that would fit into spark plug and dipped it into cylinder. When I pulled it out the very tip of the paper towel was wet - and yes, it was the coolant. So.. You probably should not wait too much and pull the plugs, see if any is coming out with lots of resistance and then dip something into that cylinder. Do this after the car has warmed up completely so there is high pressure in the cooling system that will then leak into cylinder. Let it cool a bit so you can work and remove plugs and do the check.

And there are none of the usual suspects in my case - the cooland is clean, there is no foam in oil, the car basically does not even overheat. So I was thinking no it cant be head gasket. Or a crack. I should have done this check earlier. Now I will have lots of buildup in that cylinder because it was burning tiny amounts of coolant possibly for years.
I did a block test tonight using a blue chemical that turns yellow when gasses from the block is detected in the radiator fluid, it did not turn yellow, we are doing pressure test next, if that is neg. I will be pulling the plugs to as you say. If that is neg. we will pull the manifold and check coolant lines there but pressure test should detect that if the case. I thinking about rigging a m3 aux water pump to my car for bleeding...
 

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ROLL TIDE!
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Given how easy it is to replace the tstat, I'd return it and get a different one. Oreilley doesn't carry OE tstats and I have seen them fail out of box as I said before.
 

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Discussion Starter · #7 ·
So to continue with updates,
- we tested for block gas, none has present
- we pressure tested the coolant system. We pumped it to 17 it dropped to 16 and held there. System ok.

So I decided to research how the bmw bleed the system and found a fantastic write up on the procedure and much more. I will post a link later.
First and I'm guilty of this as well. I originally bled the system this way but I convinced my self and from other post to change the way I was bleeding the system.

As of now my car is not over heating, my temp ranges from 210f to 215f.

Bleeding procedure:
- first stop bleeding the system when running or hot!!! That is why most are still having problems. Do not bleed while running or removing the cap while hot it will draw air into the system!!!
- when car is cold remove cap and bleeder screw.
- turn key just to on and turn heater on temp to max and fan on low.
- with 50/50 coolant poor slowly into the exp. tank, till the fluid run through the bleeder screw hole untill air bubbles stop. Pace screw and cap back on. Crank the car and run around for 10min or more, make sure to get the rpm up aswell while driving it.
- after returning let the car cool for a couple of hours take the cap off and if level indicator is ok your done if not repeat the procedure. Untill it is within the correct level.

If car overheats again you still have issues! I highly sugest doing the test I did all the equipment can be rented, use advance auto tool for the pressure test, it fits bmw.

My understanding is this system can not trap a significant amount of air, in the block or else where. Because how it is design to refill the system all the air is being pushed out as you fill it.
I know this will be controlversial for some... It is what it is.
 
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