540i coolant bleeding frustration

[knucklez313]

If you consider removing the bleeder and adding fluid until no leftover air escapes difficult then sure its hard. But removing upper rad hose to check fluid level is backwards to me. But hey that's your prerogative.

[philly98540]

Maybe I'm just adverse to mess, but I simply fill my coolant system via the expansion tank until the float needle comes up. Then I start and let her warm a bit, turn the heat on, do some revs, and then do a final top off. No venting with the screw or anything with the hoses.

I usually get a drop in level (burp out from wherever the trapped air was) after a drive or two, then I top it off again and I'm good after that. No mess and I don't mind checking it those second and/or third times. I always fill so the float is lower than "full" to allow some more expansion space in the tank.

[geargrinder]

I know jims approach is best but i am usually too lazy to pop the hose and fuss w the funnel etc. i do a couple different approaches.

i have a vacu bleeder i fill with sometimes. Helps to test seal of everything too.

Whether or not i use vac bleeder i always park on incline or better, have car jacked in front, always run it for a few minutes, revving it a little, always pump the top hose by hand to feel of its full yet, seldom fuss much with the stupid bleeder screw. Though it might actually do a little something when on an incline i will say.

Not Sure why people find it such a misery. If i quick and dirty it, maybe i have to top off.2-3 times. Normally. 1-2 and the 2nd is not much. If i bother putting my mind to it i can maybe get it down to 1 top off, but really dont sweat checking it a couple times. Also underfill FTW of course.

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Maybe I'm just adverse to mess, but I simply fill my coolant system via the expansion tank until the float needle comes up. Then I start and let her warm a bit, turn the heat on, do some revs, and then do a final top off. No venting with the screw or anything with the hoses.

I usually get a drop in level (burp out from wherever the trapped air was) after a drive or two, then I top it off again and I'm good after that. No mess and I don't mind checking it those second and/or third times. I always fill so the float is lower than "full" to allow some more expansion space in the tank.

LOL. You basically said exact same thing i did.

[JimLev]

When filling just thru the expansion tank until its fill right to the very top doesn't fill the water pump completely or the tube(s) running from the back of the water pump to the rear manifold on the back of the heads. I can always add at least another quart or more into the top hose.

[rf900rkw]

There are three totally different cooling systems in the US E39s. M52, M62, and M52TU/M54. Each has it's own quirks and takes it's own procedure.

You can bleed any of the systems first time without opening a bleeder or before you (over)heat the engine. Just gotta be smarter than a pocket of air..

[philly98540]

Yea, different systems on the various engines. It seems the i6's need more care with the filling/purging than the 540's. Maybe because the head is higher up.

I've been living with this 540 for about 14 years now. I used to fuss more with getting all the air out, but I find what I listed above works well and is very easy for me. I do let it run and get flowing during the initial fill and top off. Best part- no mess(none). Personally, I hate glycol. For some reason, I'd rather get axle grease and gasoline all over me than deal with a glycol mess. Strange personal issue I guess. LOL.

If I was running a shop, and had to ensure the car was perfect before it left, then I'd have to make sure all the air was out before the car left the shop. Total diff story requiring it being perfect.

[knucklez313]

Yea, different systems on the various engines. It seems the i6's need more care with the filling/purging than the 540's. Maybe because the head is higher up.

I've been living with this 540 for about 14 years now. I used to fuss more with getting all the air out, but I find what I listed above works well and is very easy for me. I do let it run and get flowing during the initial fill and top off. Best part- no mess(none). Personally, I hate glycol. For some reason, I'd rather get axle grease and gasoline all over me than deal with a glycol mess. Strange personal issue I guess. LOL.

If I was running a shop, and had to ensure the car was perfect before it left, then I'd have to make sure all the air was out before the car left the shop. Total diff story requiring it being perfect.

Ha, talking about glycol messes, I was doing the coolant overhaul on my Wifes 2.7t allroad. I had just finished the 10th and final flush, had 2 liters of G13 pink coolant and water mixed. Ran the car to temp and right as I shut it off it blew the lower radiator hose dumping ALL of it in the floor. That was a miserable cleanup.

[TDIpower]

You could do the pressure test when it's hot, connect the pressure tester to the expansion tank before the engine gets hot.
Have you done the test on the coolant to see if there are any traces of combustion. That could confirm the head gasket is bad.
Your better of with the E39 than Kodak stock, at least you still have something tangible. Kodak was a customer of ours, knew a lot of their employees. Use to love going to Dinosaur BBQ in Roch and stopping at the one in Syracuse on my way home.

Doing a test tomorrow for combustion gasses in the coolant system. Then I'll know for sure.

[TDIpower]

So an interesting development, tech stopped by today and we tested the cooling system with that color changing liquid... It did not change colors indicating no combustion gasses in the coolant. Now I'm really stumped. He is too

[geargrinder]

Personally, I hate glycol. For some reason, I'd rather get axle grease and gasoline all over me than deal with a glycol mess.

I feel ya although maybe not quite as strong... Still it has that slimey slipperyness to it... And problem is most all rad related things end up CAUSING a splashy drippy mess (hard to pop any hose without causing SOME kind of last-bit-drizzle-splash no matter how you carefully drain or not ahead of time) vs say oil which is pretty easy to handle cleanly.

FWIW i buy those cheap big black plastic cement mixing basins from the local HW store now and use those as splash and drip collectors when i pop stuff apart. Way better than my previous multi-bucket system where the drip or splash always moves somehow to just past where you have the bucket no matter how hard you try.

[philly98540]

Lol. I use the same cement mixing basin too. Works great.

[TDIpower]

So the mystery gets even more baffling. Mechanic took my car and pressurized system for 48 hours... No coolant in cylinders and no combustion gasses in the coolant system. So I don't have a head gasket leak. He did test my thermostat and found it was bad...so I got a new thermostat from bmw and he put it in.

But, the coolant still is not circulating! The pump is new. I'm thinking maybe a possible plug in the system? I don't think the radiator would be plugged, it's a new radiator.

Im stumped! Any ideas?

[ninetyseven1]

So the mystery gets even more baffling. Mechanic took my car and pressurized system for 48 hours... No coolant in cylinders and no combustion gasses in the coolant system. So I don't have a head gasket leak. He did test my thermostat and found it was bad...so I got a new thermostat from bmw and he put it in.

But, the coolant still is not circulating! The pump is new. I'm thinking maybe a possible plug in the system? I don't think the radiator would be plugged, it's a new radiator.

Im stumped! Any ideas?

Im going through something similar, was overheating up to 120c while idling lately and then when i drove it would cool down to 85-90C on highway and stay there, replaced thermosat alread with the 85C of course and just replaced water pump last night, now it idles at 99C steadily and heat is good but seems like when i put the cap back on the tank the heat gets colder?

[Soeperman]

Hey Jim, I know this is an old thread but I'm definitely having some problems with the coolant. It would be great to get some of your advice. I've attempted to follow your instructions of filling the coolant through the upper hose when the engine is cold, fill until it is full which I believe I've done. The upper hose had nothing but air in the morning. I filled about 1.5qts in the upper hose before the coolant starts dripping from the radiator. Checked the expansion tank and the level is perfect. Drove around and let it cool until next morning. Checked the upper hose and there's air again. Expansion tank now has about 3/4 filled of coolant. I've tried this about 3 times with the same result. Thanks for your instructions to begin with as it did seem to help with my rough idle.

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[geargrinder]

Superwrong thread superdude. You got a I6, not V8. Some of the principles are same, but you have a bleed screw on the motor that the V8s don’t. Go look up the threads on I6 bleeding, there’s tons explaining it in detail.

[JimLev]

Like GG said, different animal. If the hose still has air in it the coolant must be going somewhere.
The last I6 I messed with (on the side of the road) all I needed to do was keep adding coolant thru the bleed screw on the tstat housing, think we had the engine running when we did this.
If your top hose is empty then you can be sure there isn't enough coolant in the waterpump to make it work. Good luck.

[Soeperman]

Sorry I forgot to update my vehicle but I have a 2002 540i/6 earlier this year. Sold the 530. Car also have never overheated . Sits between 105-109 operating temp. No coolant residue anywhere found.

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[JimLev]

So how do you know the hose is empty? Did you disconnect it?

[Soeperman]

I squeezed it by hand first to get a feel for it which felt empty. Then I opened it to inspect and it was empty. The expansion tank however is 3/4 full. I think I followed the instructions correctly by filling the upper hose cold in the morning and making sure the expansion tank level was correct. Drove around and did inspect the hose afterwards and it was hot with coolant. Checked the next morning and the upper hose felt like there's air and the expansion tank is 3/4 full which is well above the line. No leaks of any kind, I've inspected all over including the back side. No overheating. I'm kinda lost at this point. And thank you again for the help.

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[ninetyseven1]

Well , I only know the method on the V8. Its as simple as this: with the engine cold, remove the top hose. You should have coolant spilling out. If not, then its under filled. Remove the expansion tank cap and start filling the upper hose until the hose wont take anymore. Put the hose back on , tighten it up. start car, give the upper hose a few sqeezes periodically and then put the cap back on, drive the car. Let it cool down and pull the top hose again and see if any coolant spills out, It should. if not, its under filled. That is it.

[R Shaffner]

Fill the system with the bleed screw removed. If there's a large pocket of air in the system, it will prevent coolant from fully entering the system. I start the car with the bleed screw removed too and blip the throttle slightly to dislodge any remaining air. This should be a simple task.

Bingo. This reminds me of the old debate between gapping points vs. using a dwell angle. (I know I just lost many of you.) The point is: If you want to make sure things are working a certain way while a machine is running, observe it while it's running.

When refilling an empty 540i cooling system, I do the following:

1) I fill the expansion tank, which gets coolant to the pump, block, and lower part of the radiator.
2) I have the rest of the 50/50 mix ready to pour in
3) I remove the bleed screw
4) I start the car and turn the heat on
5) As soon as the car starts the red plunger will drop and I'll add some coolant (as the pump sends coolant to the head and heater core)
6) Then I wait a few minutes with the engine running until the thermostat opens
7) I keep adding coolant whenever the plunger tells me to.
8) When the thermostat opens, I can feel hot coolant flow into the top radiator hose. As the radiator fills, I'll see coolant sputter out of the bleed hole. When the bubbles stop and it's just coolant, I know the radiator is completely full. Then I put on the bleed screw and expansion cap.
9) After the engine cools (same or next day), I add coolant as necessary.

Has worked well every time. I like it because it works on level ground and I get to see and feel the pump working and the thermostat opening. When I see just coolant coming out of the bleed screw, I know for a fact that the whole system is working.

Biggest problem is the coolant dripping down. Best done outside. Worse if one still has the stock fan that will hurl it all over. Not a problem for me now that I've removed the fan.

[geargrinder]

Sounds like the right amount of coolant is in the system but you need to get the air to bleed over to the exp tank?

Although mostly I find the bleed screw to be pointless, this might be case where it helps. See if that will help bleed the last air out from the intake hose side. Also try and park car on little slope if possible, that helps get all the air over to the tank.

[R Shaffner]

Curiosity got the best of me today, and I had an old M62 expansion tank in my parts car, so I took a hacksaw to it. That's been done on this (and/or other) sites before, but I wanted to make a different cut. I wanted to see exactly what happened to the flow of coolant from the skinny top radiator tube (the "vent hose" on realoem). The tube connects to the expansion tank by the bleed screw, so we know that's where the air/coolant go, but what do they do when they get there?

If we take the expansion tank cap off we can see a small hole part-way down the throat of the tank, and it's positioned like that's where the excess air and coolant might flow. But if we examine the cap we can see that when the cap is on the hole is between 2 0-rings on the barrel of the cap. And if you saw the cap in half, as I did, you'll discover that pathway does NOT vent to anywhere when the cap is in place. (I believe it's called a "control" pathway. More on that later.) So I knew that wasn't the answer.

Here is the best picture from my hacksaw exercise today. On the left is the throat of the tank, where the cap goes. Part way down, on the right wall just above the white vertical tube, you can see the little hole I mentioned above. On the right, you can see where the vent hose attaches and the threads where the bleed screw goes. The interesting part is what happens when the two paths come together in the white tube in the middle.

Attachment 641024

Or rather, I should say when the two paths DON'T come together in the white tube, because they are linked only when both open out near the bottom of the tank. Take a closer look at the top part of the white tube that is cut-away, and you'll see that there's a wall between the two sides. That wall extends almost to the bottom of the tube, and there's a hole in the side of the tube right where the wall stops. So it's basically like two different tubes that are designed to go down into the coolant that is usually in the bottom half of the expansion tank.

This explains a lot. For starters, it explains why BMW added the bleed screw. If one simply filled the expansion tank without opening the bleed screw and circulating the coolant (i.e., like filling the system on a normal car), then the top part of the radiator would remain unfilled.

It also explains why the radiator can be full of coolant, and that coolant remains at that level (higher than the level in the expansion tank), even when the cap of the tank is removed. Because that pathway from the hose goes down the right side of the white tube (in the picture) and opens up under the coolant level, so there's no way for air to get inside the radiator and let the coolant out. (Of course, that's why BMW went through all this trouble. If the expansion tank could be above the level of the radiator, then all this unusual engineering wouldn't have been needed.)

And it explains why the level of coolant in the expansion tank rises when I unscrew the bleed screw. (On a cold engine with the cap removed, the float and red stick will rise when one loosens the bleed screw.) I believe that lets air past the screw into the top of the radiator. That lets some coolant flow backwards in the system, back into the expansion tank.

When I did that the red stick went from 3 inches below the top of the expansion tank to 2" above. I put the cap back on with it that way, drove it around, got the car up to operating temp, and parked it. When I went out the next day the red stick had dropped down again, to the -3 inch level. And once again when I loosened the bleed screw it came back up.

So, even though the bleed screw helps when re-filling, the system is designed to be somewhat self-bleeding. In other words, when one is driving around any air in the system will end up along the top of the radiator. When the coolant gets hot and expands, that air is forced along the tube, past the bleed valve and down into the expansion tank. If there's enough air to get forced out of the white tube at the bottom of the tank, it will leave that pathway and float up to the top of the tank. Any air that doesn't make it out of the bottom of the white expansion tube will stay the tube and/or the hose, expanding and contracting and not hurting anything, unless that little bit of air gets bled out too.

And finally, that explains why all these different methods for bleeding the system work. All we really need to do is get it close, making sure there's enough coolant to work, and then check it again after it cools. Over time the system will force out almost all of the air the we might leave in the wrong place.

At least that's how I see it. Always open to others' thoughts and insights.

[JimLev]

I sawed one apart a few years ago and made a drawing of it showing all of the chambers. Will post the drawing later.

I had 2 dwell meters but gave them away a few years ago. I still have a timing light that I haven't used in years.

[philly98540]

Great explaination Shaff.