528i M52 cooling system bleeding, overhaul, overheating

[e39dream]

Ok so you have a BMW 528i with the "rock solid" m52 engine. If it's so rock solid then why do they overheat and warp/ damage cyliner heads you ask? Because you don't understand how the cooling system works, you stupid american.

I think of the cooling system as a pressurized, closed circulation system. That is, the coolant is forced through the system at a greater pressure than domestic vehicles, and is contained in a sealed system.

The components:

1. radiator.

http://www.realoem.com/bmw/showparts...05&hg=17&fg=05

Purpose: coolant is forced through the radiator and is air cooled through the core of the radiator.

*check for: any leaks no matter how tiny, check that the front of radiator is clean from debris, remove fan shroud and check hose that is under it leading to expansion tank. Make sure drain is closed snugly.

two well known replacement brands are Behr and Nissens.

2. expansion tank:

http://www.realoem.com/bmw/showparts...35&hg=17&fg=05

Purpose: provides a means to top off coolant and is where the excess coolant is forced on a hot motor. You should keep this full of coolant to the "full cold/ kalt" line, top off on cool engine.

*check for any cracks or leaks, examine on warm engine- this little tank has caused alot of frustration in the past over "mystery leaks"

I am not aware of any aftermarket repalcement for this part, that doesn't mean they aren't out there.

3. mechanical fan/fan clutch:

http://www.realoem.com/bmw/showparts...44&hg=11&fg=35

purpose: this fan has a clutch in it that is designed to lock up as the engine gets hot, making the fan pull air through the radiator and over the engine. These clutches can go bad, I've seen an e39 540i with a seized fan clutch have the plastic fan explode and literally pound the hood with fist sized dents from the inside out.

*To test yours, start your car on cool motor. CAREFULLY take a rolled newspaper and attempt to stop the fan. It should stop no problem, if you can't stop it you need a new fan clutch, simple, huh? If you find it needs to be replaced, you'll see it can be a pain to remove. There are special tools available that hold the four bolt heads on the pulley so you can turn the fan.

My approach was to grab the pully with channel lock pliers and then turn the nut on the fan. This worked, but also broke the pulley which had to be replaced. Sooo... you either buy the special fan removal tool or run the risk of replacing the fragile pulley. BMW dealerships keep the plastic pulley in stock- imagine that.

You can get a new fan/clutch as well as the fan removal tool from any major BMW parts house like bavauto.com

4. water pump

http://www.realoem.com/bmw/showparts...46&hg=11&fg=35

purpose: a no brainer- the water pump is responsible for the pumping/circulation of the coolant through the components of the cooling system.

*check the pump for any play in the impeller shaft. With the belt off be sure it spins freely, there should be no bind or tough spot and it should be easy to turn. If you have tried everything and still overheating your impeller may have come off the shaft, it's happened.


5. thermostat and thermostat housing:
http://www.realoem.com/bmw/showparts...46&hg=11&fg=35

purpose: the thermostats on these are a lil different as well. only use OEM parts in this position. The thermostat opens and closes to keep the engine at a consistant operating temp. These don't go bad often and are generally blamed when something else is really wrong. The housing's purpose is to contain the theromstat and provide and inlet and outlet to the radiatior.

*replace the thermostat for good measure and check that the housing is properly fitted and leak free.

I have found an all aluminum thermostat housing available for the M52 through an ebay search, may be a worthwhile upgrade.

6. Coolant hoses

http://www.realoem.com/bmw/showparts...55&hg=11&fg=35

this chart does not apply to my vehicle, might match yours:
http://www.realoem.com/bmw/showparts...38&hg=11&fg=35

Got a mystery coolant leak? Maybe it's one of those hoses, huh?

*not much to say here, inspect the hoses for leaks and tears and replace as required.


7. pusher/helper fan

http://www.realoem.com/bmw/showparts...=64&fg=55&hl=9

Purpose: this fan has a few different speeds that are selected based on the cars needs. This fan helps cool the radiator as well as the A/C system.

*to test fan, turn on air conditioning to like 62 degrees/ climate control fan on high and make sure the snowflake button is lit up, if not push it, with the car in park. go out and look up into the grille. If it's spinning it works You may also test it by applying 12v directly to the control box, you are on your own there. This fan is another area that you want to keep clean and free of debris.



Now that we have examined and replaced anything faulty, let's fill it with coolant and bleed the air out of it!

here is a generic tutorial to bleed the system out , I'd appreciate it if one of our forum "experts" could elaborate- I know Jim has a trick or two that makes this easier.

http://www.bmwtips.com/tipsntricks/JC/Overheating.htm


This part is under the shroud I mentioned and connects the radiator to the expansion tank via a small diameter hose:

http://www.bmwtips.com/tipsntricks/r...-vent-pipe.htm



If you are having troubles with overheating or 528i cooling system post it in this thread first before making a new one and I will do my best to help. From here on out if I see an 528i overheating thread that has not gone over this troubleshooting list I'm not even commenting. I think this is a solution to an ongoing problem- let's put our heads together and keep our bimmers running cool and strong!


Any other tips, tricks, sources for parts and 528i cooling system concerns are welcome!

This write-up is linked later in this thread as well, it is a very good tutorial with pictures and additional info:
http://www.bimmerboard.com/forums/posts/199986

[PENER]

this thread should be a sticky!

great job e39dream

[e39dream]

Thanks alot Greg- just trying to give a little back to this community. I noticed an increase in m52 cooling problems (and alot of new 528i guys here) and just get tired of beating the same old responses into the keyboard At the same time though I hate to see someone post here and not get helpful info. It's a labor of love.

[brandon5069]

This is great...

Good for you E39dream. I second the sticky creation request.

[Karen1122]

I am headed to flush my cooling system tomorrow (2000 528i with 125K miles). There have been no problems to date except for squeeling when the engine is cold so I am going to have them check the belt, tensioners and idler pullies. Is there anything else which is commonly checked out??


PS this is great info and I second that it should be a stickey

[e39dream]

Hey Karen1122- it sounds like you have a good idea what needs to be done. Be sure to replace or repack grease on any bearings on the idler pulley if the squeak persists.

[VacMan]

Good post, thanks.

I have a bit of a different issue with mine. The symptoms indicate to me that the thermostat is stuck open. In colder weather the temp. gauge will not reach even halfway to what I would consider normal operating temps. Once the day warms up, it gets to the halfway point with no issues and holds there.

I had no idea that the thermostat is remotely controlled. Is it possible that this has something to do with the "electric heating element in the block?" I'd love to replace a sensor rather than pulling apart the cooling assembly.

Thanks,

Tim

[e39dream]

thats a weird issue vacman- I looked up your symptoms in my TIS and came up with nothing. I'd post a thread about it and try to get it figured out though- that doesn't sound right at all.

Even when it's 10 degrees here like right now my car's temp needle will be exactly halfway on the guage within a 10-15 minute drive.

[ashamans]

if the thermostat is stuck open the car will not heat up at due the engine being cooled all the time, not given a chance to warm up

[TomiJ]

I don't know if my 528i engine is an m52, but I experienced something very weird today. While sitting at a light, the temp needle slowly went to the red. After I started driving, it went back to the normal position and never happened again.
Any ideas, group? 96k on the clock.
Thanks.

[e39dream]

hey Tom- your 1998 528i is indeed an M52 and the symptoms you describe indicate either a low coolant condition, a bad fan clutch or helper fan, possibly a combination of two of those things. This exact thing happened to me at a taco bell drive up while waiting behind the other cars, I found there to be air in the system and coolant low. A quick top off and bleed corrected the issue and it's never happened since.

[TomiJ]

Thanks e39dream, appreciate it. Just got the ride a couple months ago. Now I see from reading this thread that this is a common issue with the 528i's.

[e39dream]

Just be aware that your cooling system needs some light maintenance once in awhile and you'll be a happy camper.

[bimmerspeed]

Hello there Tom, my 528 started having the same problem.the gauge needle would slowly cimb to Red/Hot while on idle and would go back to normal once i pressed the gas. Or if I had the car in parking and if i pressed the gas it would go back to normal. I first replaced the thermostat and still with the same problem. then I changed the Fan Clutch and the problem still was there. I then took my 528 to a bmw shop were the master tech said my radiator was clogged up somewhere in the bottom causing it to over heat. Im getting it back tomorrow. I cant wait, I already miss driving it .. Good luck..
I have read other threads.. where people have had the similar problem of over heating while idle and it seems like a high percent of the time it gets fixed by replacing the fan clutch..

Well Good luck again..

[qcdstick]

I also have the problem with the car never warming up, even on a 3 hour drive. The prognosis in the Mechanical Help forum was a stuck thermostat. I bought a replacement from an autoparts store, and plan on putting it in this weekend. Are there any step by step tutorials on how to do this? Given that it seems to be a common issue I think it would be a worthwhile writeup. If not I'll just wing it and try not to make "too" big of a mess :-)

[TomiJ]

Thanks Bimmerspeed, Now the dang thing is intermittently starting to overheat while driving, which I reckon is tad more serious. I was going to bleed the system and top off with coolant first and see what happens.

[328iThizz]

for the fan clutch, i thought it was the other way around? if you CAN stop the fan, then you need a new clutch. if not, then its fine.

[e39dream]

for the fan clutch, i thought it was the other way around? if you CAN stop the fan, then you need a new clutch. if not, then its fine.

alright 328ithizz, you seem to have a hard time understanding this particular part so I'm going to take more time to explain it-as well as for future viewers.

The mechanical fan has a clutch on it. Think about the very definition of the word clutch, think about how a manual 5 speed car's clutch works. An event causes the clutch to operate, in a car's case the event is your foot releasing the pedal, in this fan clutches scenario that event is heat.

When you start your car with a cool motor (as in first time starting motor for the day) you should have no problem stopping that fan with a rolled up newspaper- if it does not stop the fan clutch has failed and is seized in a dangerous "always on" setting. It must be replaced.

The fan's clutch activates and allows the fan to be turned by the engines power only after a certain engine temperature has been reached. The fan clutch may be broken and never activate- meaning it's always "stoppable" with a newspaper no matter how hot the engine is. In this case the fan clutch should be changed as well, it's shot.

YOUR ABSOLUTE BEST BET IF YOU ARE HAVING OVERHEATING ISSUES AT STOPLIGHTS OR AT IDLE OR ANY OVERHEAT ISSUE IS TO SIMPLY CHANGE THIS PART WHEN YOU REVAMP THE REST OF THE COOLING SYSTEM.

This fan can be dangerous if it fails- is the 100 and whatever dollars a new fan clutch costs worth ruining a perfectly good hood, or worse yet taking a couple thousand dollar cylinder head with it? I didn't think so. If your 528i has over 120k miles change the damn fan clutch.

Here's a thread where the fan clutch failed:
http://forums.bimmerforums.com/forum...d.php?t=781493

[acschnitzerbill]

thats a weird issue vacman- I looked up your symptoms in my TIS and came up with nothing. I'd post a thread about it and try to get it figured out though- that doesn't sound right at all.

Even when it's 10 degrees here like right now my car's temp needle will be exactly halfway on the guage within a 10-15 minute drive.

I hjad the same problem. Changed the Thermostat and it still did it until. I opened the bottom screw on the radiator and took a water hose in the fill hole, then I opened the bleed screw. With the cold water running through engine in normal running mode I heard a "Klunk sound and then the top hose and bottum hose had no hard pressure. Since then no problem. Oh I had the thermo in backwards

[TomiJ]

Not to seem like a dope, but is the bleed valve a long tube like device to the left of the radiator with a small cap on it?

[qcdstick]

I also have a question on the bleeder valve for a 528, because there appears to be 2. There is one on the thermostat housing, and appears to be another one on the expansion tank (doubles as the screw that locks the expansion tank in place). What one are you supposed to use when? Or is the one on the expansion tank not a bleeder valve at all, but rather simply there to lock the expansion tank in place?

I'm going out to play around with it today, maybe I'll get it figured out, but if someone could post a definate answer in this thread I'm sure it would help a lot of 528 owners.

[VacMan]

Not to seem like a dope, but is the bleed valve a long tube like device to the left of the radiator with a small cap on it?

No, I believe that is for the AC...I'm guessing a port to recharge it. The bleed valve on the radiator is just to the right of the radiator cap (as you're facing the car.) It sits flush with the surface and has an X in it. I use a long-handled Phillips screwdriver to loosen it slowly while the car is idling.

I've been using this the last few nights after driving home to burp the system. It seems that each night it takes less time before the coolant runs clear with no bubbles, but that could just be my imagination.

I also have a question on the bleeder valve for a 528, because there appears to be 2. There is one on the thermostat housing, and appears to be another one on the expansion tank (doubles as the screw that locks the expansion tank in place). What one are you supposed to use when? Or is the one on the expansion tank not a bleeder valve at all, but rather simply there to lock the expansion tank in place?

I'm going out to play around with it today, maybe I'll get it figured out, but if someone could post a definate answer in this thread I'm sure it would help a lot of 528 owners.

See above.

Tim

Here's a pic of the bleed screw sourced from a terrific cooling system writeup I found HERE.

[nightkrawler]

didn't read the entire thread and links but i'll add the following, sorry if it was mentioned already. 1) removing the fan clutch- after you've committed to doing the job, get a can of pb blaster. spray an ample amount where the nut meets the wp pulley. go about doing the preliminary work and when you get to the part where you have to remove the clutch, do this. get a long pry bar(preferably grind some material off the point of the bar so it is not as thick). standing in front of the car looking at the engine, pry bar in left hand, insert it down and catch the tip of it between one of the bolts on the wp pulley. with you right hand insert your 32mm wrench down onto the nut. put force on each and the fan should easily loosen.

2) bleeding the cooling system- the "bleeder" screw needs only to be opened one time and that is when you are refilling the cooling system to allow the air out of the system. when you are ready to refill the system, remove the screw. slowly pour coolant into the expansion tank until you start to see a bit intermittently coming out of the screw hole. pour even slower now until you see a steady stream of coolant coming out. now replace the screw and start the car. once its up to temp and cooled back down re-check the level. i've watched guys mess with that screw for 20min trying to get air out and doing nothing but making a mess.

here's a crude diagram of what i mean about the pry bar to hold the fan clutch,

[VacMan]

2) bleeding the cooling system- the "bleeder" screw needs only to be opened one time and that is when you are refilling the cooling system to allow the air out of the system. when you are ready to refill the system, remove the screw. slowly pour coolant into the expansion tank until you start to see a bit intermittently coming out of the screw hole. pour even slower now until you see a steady stream of coolant coming out. now replace the screw and start the car. once its up to temp and cooled back down re-check the level. i've watched guys mess with that screw for 20min trying to get air out and doing nothing but making a mess.

Interesting points. I read the following from the link E39dream posted above, which is why I used the screw to bleed the system.

Over Heating Check List
by Jim Cash on 2002-11-04 I would suggest checking the coolant, and making sure it is bled properly - which can be a rather involved process to do it correctly.
The basics
Cold engine
- check that coolant level is correct
- Ignition on but engine not running
- set heter temp settings to max
- set fan manual to one of the lower speeds
- start engine and within 30 seconds rev it 3-4 times up to 3000rpm
- shut off engine before end of 30 seconds (before it starts to heat)
- reset climate to normal settings
- recheck coolant and top up if necessary.
Hot engine
- take car for a run to get up to operating temp
- using caution - slowly open the bleed valve (steam and bubbles may come out)
- close as soon as you see liquid coolant without excessive bubbles.
- do not overtighten this as they are plastic threads. Just snug till it seals fully.
- after engine cools check the coolant level again and top up if necessary.
Check coolant level every few days for a few weeks and top up again if required
- repeat the Hot engine bleed process again.
If coolant keeps droping after 2-3 top ups have the system pressure tested.
If you are still getting over temps have it analysed by a dealer. The temp is controlled by the engine computer so there may be another fault.
Cheers
Jim Cash

[e39dream]

the m52 can take 3-4 "bleeds" before all the air has been purged from the system. The Over heating checklist is correct.

I also wanted to add that most of this info in this thread applies to any e39, except the part numbers obviously.