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DIY: The trick on how to fill the M52, M54 coolant

165K views 69 replies 26 participants last post by  BMW530iT 
#1 · (Edited)
Nothing new, but the cooling system on the 6-cylinder engines has baffled me for a long time, why it is too difficult to bleed the air out etc.

So I will do a short and sweet DIY for those who wonder how to fill the coolant after performing cooling system work (such as cooling overhaul or water pump replacement etc.).

1. Take a minute to study the design of the E39 cooling system (see figure below). When the car is cold in the morning and you start the engine: during the warm-up phase, there is some hot coolant getting into the driver's side hose, "ready" to go through the radiator once the thermostat is open. Think about the thermostat as the "flood gate".

2. Now once the thermostat is open, the flow direction is:
Engine ---> driver's side hose ---> upper radiator ---> across radiator (to be cooled down)---> lower radiator hose ---> through thermostat area ---> Water Pump to cool engine.

- So in a normal engine at operating temp, the lower hose is considered the "Cold" side because the coolant has been cooled by the radiator but it is still somewhat "Hot" to the human hand anyway (maybe around 60-70 deg C, enough to burn your skin!). Here is the direction of coolant flow (from M54 but M52 flow is the same):

Study this M54 layout:


3. After some work in the cooling system is performed, re-filling the system is tricky because of the goofy design.
I just took another detailed look at my car again and here is the trick.

- Normally (if you haven't done any work on the cooling system at all) you want coolant at "KALT" level (or COLD level in the morning), but during re-filling, don't worry about it for now.

- Look at the thermostat housing, there is a small hole connecting the right and left sides of the thermostat housing. This hole allows air trapped in the lower radiator hose to travel through the hole to the driver's side to be bled out the bleeder screw.
(See GREEN arrow in pic below).

- If your car is on level ground, look carefully, you will see that the thermostat housing bleed screw (#1) is located at the same level as the reservoir neck and not at the "KALT" mark on the reservoir.

- Once you understand the above design, re-filling is easy.

a- Fiil coolant slowly. But I will add some tips...

b- Be patient and be patient, the hole connecting the (R) and (L) sides the thermostat housing is very small, maybe 1/16" or something like it. So air bubbles move through it very slowly.

c- Fill coolant up to the reservoir neck until it stops filling. Now some air is trapped in the lower radiator hose. Give it a good 5 minutes to settle there. Fill again until coolant fills to the neck, which is about 3 inches above "KALT" mark.

In the mean time, listen to some music and drink some beer...:)

d- Now open the thermostat housing 1 full turn (it takes 5 full turns to remove the bleed screw, so 1 full turn is all you need), air will come out slowly because the hole in the tstat housing is very small. When coolant comes out, close the bleed screw.

e- Don't start the engine yet, repeat the steps a through d a few times (another beer won't hurt...:)) until you are sure all air is bled out of the bleed screw.

f- For the 1st fill, if coolant is at the reservoir neck, then it is OK, air trapped in the engine will be expelled out when you run the engine. It will eventually settle down to "KALT" level anyway. If you are worried, then use a turkey baster to remove a bit coolant so it sits just below the neck prior to running the engine.

This should do it. Be patient and be patient when filling the cooling system!!!

4. The above little trick will help get rid of air outside of the engine.
Air Lock (air trapped inside the engine behind the thermostat) is another issue. Do a search.

 

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#2 · (Edited)
howdy c90,i had an e34 m20b25 and currently a '97 528i m52b28.this is how i bleed my cars with ease and success all the time:

1. open both bleeder screws
2. fill up radiator with water till full
3. close radiator bleeder screw
4. blow into radiator filler neck till water comes out of engine bleeder port.ensure nil air bubbles.tighten engine bleeder screw
5. top up water.open radiator bleeder screw
6. blow again till water comes out of radiator bleeder port.ensure nil bubbles.tighten radiator bleeder screw.
7. you're done.
8.to fill coolant,drain the reservoir tilll empty and fill up with coolant.no bleeding required.
9. step 6 will require you to top up water approx twice
10.i live at the equator so coolant used more for water pump lube and antirust purposes

cheers
 
#3 ·
2. fill up radiator with water till full

4. blow into radiator filler neck till water comes out of engine bleeder port.ensure nil air bubbles.tighten bleeder screw
Welcome to bimmerfest.

#2. Water maybe OK for where you live (Malaysia) but even so a 50-50 mixture is recommended for protection up to boilover temp.

#4. Blowing may sound like a nice idea but Coolant contains Methanol, even trace amount will be converted by your body Alcohol Dehydrogenase enzyme to "Formic Acid" = blindness!
So don't blow into the reservoir neck with your mouth if you care about your eyes!
 
#5 ·
....like given fron sky

I was cheking a leakage that I found on the upper radiator hose and as soon I read your thread I was able to fill again the coolant that I lost while I took out the upper hose.
I'm just amaze how easy this hoses con be change.

PS about that blue coolant....it got a sweet taste...:D
 
#7 ·
CN90 - another question...it is my understanding that the 530 (M54) has an auxillary pump and I've several instructions on this board stating that when refilling coolant that it's advisable to turn the key to the accessory position, turn the heat all the way up, and let the pump distribute the coolant through the system, then bleed. Any thoughts? I am anticipating a cooling system overhaul this summer and the only thing I fear is the bleeding process.
 
#12 · (Edited)
The Aux Pump issue is a headache. Dealer has the tool to activate the Aux Pump.

No worry, I addressed that in post #19 here: basically you fool the system into activating the Aux Pump:
http://forums.bimmerforums.com/forum/showthread.php?t=1423821

PS: I forgot to attach the picture showing the Small Hole connecting the (R) and (L) sides of thermostat housing. Whether it is Aluminum or Plastic Housing, the hole is there. This is why re-filling it requires patience!!!

 

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#9 ·
Another great step by step DIY

I too have heard that the aux pump (definitely there if the REST function is there) is the way to go. Otherwise, won't it have bubbles when the water moves through the heater coil?

No matter where you live, you need 50/50 coolant. The antifreeze properties are fine and all but the boiling temperature of water is considerably affected by the addition of the coolant as well.
 
#10 ·
lol and forgot to add, (since its takes around an hour or more.. remember we cant be too careful with our baby now can we.. to fill up the coolant), and weve been chugging down the beers the whole time, dont drive right after the job O:). also, any tips on filling up coolant on m62 and m62TU engines? (and s62 while were in the field for the m5ers here)
 
#11 · (Edited)
#13 ·
I use the aug pump every time I fill my car and others I have helped. I raise the front of the car--open the bleed screw hole--cut the ignition on and the heat at it's highest setting . You can hear the pump come on
then you start pouring the coolent into the expansion tank--when the fluid starts coming out of the hole at the water [pump screw it down--when it starts coming out at the expansion tank--screw that one down--then fill to the proper level in the tank and your done--Gotta add--I have checked and rechecked--never have I had to add fluid--and never had any air in the system when doing the refill this way
 
#15 ·
I know that you have asked CN90 about this--I'm chiming in --on your model car the stat is controled electronically--on CN90's car it's just the stat--on his model the hole needs to be there--on your model
I wouldn't try to drill anything--might cause damage to the electrical unit.
 
#18 · (Edited)
1999---> 2003: electrical thermostat. If you decide to drill, do it very carefully. If not, then you are prob OK anyway.
I have a 2002 I6. Am bleeding as per this DIY (confusingly because nothing is coming out of the expansion tank bleeder hole and it's only a dribble out of the thermostat hose bleeder hole (turned 1 turn open)). Kind of confused.

Will look for the "auxiliary pump" bleed method ...

Anyway, I saw this part about "drilling a hole". Why? Where?
 
#23 · (Edited)
...d- Now open the thermostat housing 1 full turn (it takes 5 full turns to remove the bleed screw, so 1 full turn is all you need), air will come out slowly because the hole in the tstat housing is very small. When coolant comes out, close the bleed screw.
I need to revise this step #d. I just changed my Tstat Housing seals and did this to speed things up a bit.
d. Instead of unscrewing only 1 turn, you can remove the bleeder screw (labeled #1) completely and set it aside in a safe place to avoid losing it! This makes filling coolant faster. Pour coolant into reservoir slowly (a funnel helps), it will take roughly 2 minutes to fill the engine block completely.
- Keep looking down the bleeder screw port, you will see coolant rising slowly, then it will spill out of the bleed hole. At this time, re-install the bleeder screw.
- You will notice that coolant will sit roughly 1" to 1.5" above the KALT mark. Nothing to worry about as long as you have about 2" of air space at the top of the reservoir. With driving cycles, heat/cold cycles, some air will come out and the coolant level will settle down with time.
- On the other hand, if you are worried, then suck the excess coolant out using a small syringe.

--------
I recently changed my Tstat seals and for my curiosity, decided to probe the coolant passages using electrical wire and my finger!
I confirmed the coolant flow as follows:
- The WP circulates fluid from solid orange line from engine and solid blue line from UPPER Radiator Hose ---> dotted blue line (behind the thermostat) into the WP itself. This brings cool fluid into engine.
- Then hot coolant builds up in the engine block and comes out in the dotted purple line ---> solid purple line into the upper rad hose.

- There is no direct connection between #1 (blue) and #2 (purple) areas.
- So air trap behind the tstat is a distinct possibility in the M52 engine.

 
#30 · (Edited)
--------
I recently changed my Tstat seals and for my curiosity, decided to probe the coolant passages using electrical wire and my finger!
I confirmed the coolant flow as follows:
- The WP circulates fluid from solid orange line from engine and solid blue line from UPPER Radiator Hose ---> dotted blue line (behind the thermostat) into the WP itself. This brings cool fluid into engine.
- Then hot coolant builds up in the engine block and comes out in the dotted purple line ---> solid purple line into the upper rad hose.

- There is no direct connection between #1 (blue) and #2 (purple) areas.
- So air trap behind the tstat is a distinct possibility in the M52 engine.

howdy cn90...just thot i'd share.looking at yr pic,you mentioned about the water pump removal bit.....to pry slowly with screwdriver little by little all around to remove WP.well i recently replaced the WP on mine without having to do this.(mind you the WP was stuck fast)if you notice on the WP there are 2 additional THREADED bolt holes apart from the existing 4 mounting holes?well these are for ease of WP removal.find 2 bolts of the same diameter and thread,screw in evenly and the WP will be 'pulled' out............. :thumbup:
 
#24 ·
I was bored.....so I played around with my old coolant reservoir and this is the design:

- Hot coolant expands and exits the radiator via the "Snake Hose" (Orange Color).

- The reservoir has an internal pipe attached to the nipple, so coolant enters the reservoir and exits at the very bottom of the reservoir (Orange Arrow).

- If there is air in the Snake Hose, it may create an "Air Lock", thus the Bleeder Screw (Green Arrow) is there to help get rid of the air trapped in the radiator.

 

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#25 ·
this is the design
I love it. Pure and simple!

And, best of all, it makes sense.

Can someone do the same for the newer (slightly more complicated) E39 expansion tank? ( I can't. )
Note: D = distal, M=medial (the medial hose is closer to the centerline of the engine; the distal hose is closer to the fender).
 

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#26 ·
Just replaced the radiator and thermostat in my '97 528i.... All went well until I fired it up and went for a test drive around the block. let the car warm up for ten minutes then took off. Within minutes of driving it nearly went to red line. After getting it home, I rechecked the coolant level and that was fine. However after checking the top and bottom hoses I realized they were both super tight and ready to pop from pressure. I let the engine cool down and rechecked the coolant level, it was a smidge low so I filled it to correct level, let warm back up and went for another test drive, did fine for ten minutes or so and as I was on my last turn before home, red line. Same deal, major pressure in the top and bottom hoses, and when I took the radiator cap off, it gushed fluid. It seems as though there isn't and flow...? Maybe its the water pump? Also, on my second test drive the heater worked as normal, when it got hot the cabin heat blew cold air consistently. Stumped here and could use some experienced advice!!!!!!!!!!!!!!!

Rich
 
#27 ·
Maybe its the water pump?
We should probably take this over to another thread as this may have nothing to do with bleeding.

But, I'm incredulous that you did all the work to replace the radiator and thermostat and you didn't also replace the water pump at the same time? (Why did you replace the radiator and thermostat in the first place? What were the symptoms?)

It's only four more bolts after the thermostat comes out:
- What brand of waterpump to buy (1)

In fact, everyone recommends replacing the ENTIRE cooling system whenever replacing any one part of the cooling system:
- Complete cooling system overhaul recommended parts list (1)

Anyway, I'm no expert but it 'sounds' like it could be the waterpump.
- Pictorial look at typical E39 cooling system failure modes (1)

Check out these videos ... but we should move this to its own thread if it no longer is bleed related:

Part 1:


Part 2:
 
#33 ·
I know this isn't a new thread, but I have to say, there are more than a couple DIY's out there for bleeding the cooling system... As I'm a "video first" kinda guy, the first DIY I saw on YT used the auxiliary pump method, so that's how I did mine... I mean, you just turn the key on, set the heat to 90* on the lowest fan setting, and that bad boy starts pumping as you're adding coolant. You can literally hear the air going out of the system as the bubbles initially cavitating throughout the system finally fall silent after tweaking the bleeder screws.

I just got onto the whole lower cluster thing, so I'm going to open it up and watch my temp on the way up to LA tomorrow... :confused:
 
#34 ·
CN90 & BlueBee you guys rock! I used tips from the both of you on a quick (60 minute) replacement of both my AC/Acc Belt and Serpentine! Your tips were very helpful and clear. I still have an unidentifiable 'whistle/rattle' sound which I thought I would resolve with a belt change? However, following the installation of the new belts, replacement of coolant, I still have the rattle/whistle when the car is idling? I welcome any ideas..

Thank you both.
 
#35 ·
omg the "thermostat drilling guy" strikes yet again :rofl:

Nothing new, but the cooling system on the 6-cylinder engines has baffled me for a long time, why it is too difficult to bleed the air out etc.
he says, when in fact THERES NOTHING HARD about bleeding the system by simply REFILLING slowly :confused: nice 1 buddy :thumbup:

if anybody wants to take refill/bleeding process beyond the level shown in the video, that is fine by me :dunno: just dont come here feeding us BS about the complexity of the procedure and ur "genius" ways of fixing whats not broken :tsk:



http://www.youtube.com/watch?v=RMkCmJ3tPkQ&feature=related
 
#37 · (Edited)
omg the "thermostat drilling guy" strikes yet again :rofl
Orxan,

Have you ever Googled Images using keyword "thermostat drilled".
There are thousands of people doing it.
http://www.google.com/search?rlz=1C...&source=og&sa=N&hl=en&tab=wi&biw=1219&bih=651

Anyway Orxan, nice try at rants against other forum members.
I do not recall that you contribute anything significant to the forum at all.
One thing is certain though, I will not stoop to your immaturity.
You need to grow up.

This is just an example from another thread:

I won't bash your car orx because I won't stoop to your childishly immature level. But I do enjoy your pathetic attempts at rants against other members. So keep going and keep us entertained with your infantile tirades. :thumbup:
 
#40 ·
Well...
I am in the process of doing the full cooling system overhaul...
I have read (feels like 20 hours of good information, and too many hours of foolish BS), both from bimmerfest, and bimmerforum, and seen near 'battles of words' between Veteran Wrenches (folks here know the threads I am referring to, without naming names), over proper ways to Bleed the air out of E39's.

I am fully confident about doing the actual work on my 2003 530i. What I am frustrated about, is the fact that there are many versions of E39 cars.
IE: 6 year span of time, with different engines, different t-stat housings, different t-stats, different expansion tanks, different plumbing (hoses), different, different, different, etc.etc.
This is obvious when you view the massive selection of parts at Pelican, or any other OEM/aftermarket parts house... ALL because each year model and engine are different...

My point is that all the EXPERIENCE (trusted wrenches) here, seem to all have older cars (97,98, 00, etc.), where some are 528's, and the others are 540's, they ARE DIFFERENT from each other.... and have basic t-stats...

Some of us have 2003's, and happen to be the 530, and THEY have the Aux. Pumps, AND electric t-stats...

I know this is somewhat rambling, but when everyone chimes in with 'what method' works for them, it still is NOT GOOD, and may not work, for everyone....

It seems like there would be a specific 'air bleeding' instruction for each and every model of the E39 !!! Since the design and parts are DIFFERENT....

Would someone say with absolute confidence which method works BEST for the 2003 530i, with the Aux. Pump, and its special t-stat housing ????

PLEASE.
 
#42 · (Edited)
Well...
I am in the process of doing the full cooling system overhaul...
... stuff deleted ...

Would someone say with absolute confidence which method works BEST for the 2003 530i, with the Aux. Pump, and its special t-stat housing ????

PLEASE.
Well, "with absolute confidence" is a high hurdle :) However, I've used the method described in the TIS for my 2003 530 (see attached) with success. I have the auxillary pump & electrically controlled thermostat, just as yours does.

I have never had any "coolant bubble" symptoms. I did have to add 1/4 to 1/2 cup the next morning or after a several hour cool down to get the expansion tank indicator rod at the exact point. But only a single time each flush and bleed; never had to add coolant multiple times.

Interestingly, the TIS instructions direct one to open only the expansion tank bleed screw. There is no comment regards the bleed screw on the upper rad hose by the thermostat.

EDIT: my auxillary pump does work. One can hear it running, it's not loud but definitely a hum when running with the key on engine off. If the auxillary pump is not working, it could well make a difference to the bleed; the pressure and flow volume is impressive.

Regards
RDL
 

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#41 ·
Also, Post the BEST bleeding method for 'every' year model and engine variant...
that would help more people than one can imagine, rather than having to read thread, after thread, after thread of multiple opinions...

Thanks everyone for the vast information available here. You help save everyone large amounts of $$$ from the Stealers.

I just want to know what works for my 2003...
 
#43 ·
I followed the TIS, just as RDL mentioned, and didn't have to add anything. It was a one time deal. Also, I only used the vent screw at the exp tank level, didn't touched the one on the upper rad hose.
All is well after 1 month.
Also, as mentione by RDL, you can hear the aux pump working and gurgling when filling up.
 
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