Nice and fast way to bleed coolant in M20

[tim88325is]

After changing the timing belt and spending frustrating hours trying to fully bleed the cooling system by having the front on ramps, getting up to temp, using the bleed screw, etc... I would like to offer the following procedure I followed.

I am sure this has been done before but I haven't seen this exact method it after searching. I have read where people "blow" on the reservoir opening but that seemed a bit crude and inefficient.

Basically, it is "back-bleeding" the cooling system, I had to do this on Triumph car clutch, the only way to force the brake fluid past a high section of tubing.

Car - 1988 325is

The only new tool I needed was a cheap $6.00 plastic "oil pump" that can screw onto the top of a gallon jug. Found it at the local auto parts store.

Important - I drilled a small 5/64" hole in the top section the outer portion of the new thermostat. Right through the embossed arrow pointing upwards. This allows a small amount of coolant to bypass the thermostat when cold.

I worked with a cold car, parked flat(no ramps) that is not running and a coolant reservoir that is nearly empty. The night before I had tried to bleed the car by the "ramp" method, it worked ok but the temp did rise when idling. I ran out of time to keep working on it. Overall the system was probably 2/3 full but I think this procedure would work as well on a completely drained system.

Remove the coolant reservoir cap and put the heat control on full.

Install the pump in the top of the coolant jug and attach the pump's tubing to the small nipple on the very top left(driver) side of the radiator, directly above the large coolant hose. This nipple normally feeds into the coolant reservoir, you need to remove the small hose clamp and hose.

Loosen the bleed screw on the thermostat housing.

Pump the coolant into the radiator until the it flows out of the bleed screw on the housing.

Close the bleed screw.

Keep pumping the coolant until the coolant reservoir starts to fill up. I actually heard gurgling sounds as air bubbles worked out.

Keep pumping until the reservoir is full.

Remove the pump's tubing from the radiator nipple. Have the original hose ready to slip on because it will spurt coolant out of the radiator.

I put the reservoir cap back on and went for a drive with perfect results. It ran cool and consistent.

I have found this method to be extremely fast, clean, and safe compared to what I had tried before.

Let me know if you have any questions or feedback!!!

[rares]

hey cool man... i am just about to do that...

[jlevie]

A better way to do this is to disconnect the small tub that runs from the reservoir to the radiator from the reservoir. Fill the reservoir with coolant and put the cap on. With the front of the car at least one 1' higher than the rear apply pressure to that tubing (blow into it) until coolant is flowing from the bleed screw and and the top of the radiator. It is important to have the front end of the car up in the air so that the radiator and bleed screw are the highest points.

Note that this won't clear ar from the heater core. To accomplish that you have to follow the normal bleed procedure (see below).

1) Using ramps or a jack get the front of the car 1' or more higher than
the rear. That will make the radiator and bleed screw the highest point
on the engine and facilitate removal of air.

2) With the bleed screw open, add coolant until no more air comes out of
the bleed.

3) Leave the filler cap off, or at least loose, and set the heat for max
temp and fan speed. Leaving the cap loose will prevent air that's still
in the system from causing a "coolant fountain" once the engine heats
up. Start the engine and allow it to warm up to operating temp. As it
warms up occasionally crack the bleed screw to release any air and top
up the coolant as necessary.

4) Once the engine is at temp bring it up to 2000-2500 for a few seconds
several times. Then crack the bleed until no more air is released. At
this point the heater should be throwing lots of hot air, which
indicates that the heater core is filled with coolant. You may have to
repeat this a few times to get all the air out.

5) Drive the car a bit, allow it to cool back down, and recheck the
bleed for air. Over the next few days you may get very small amounts (a
few bubbles) of air out of the bleed screw.

[tim88325is]

Actually, that method is exactly what I had a problems with. I just couldn't get the air bubbles out with spending hours of driving and revving the car on the ramps. Even then the temp fluctuated, telling me air was still in the system.

My system allows the two hot and cold "circuits" of cooling system to be slowly and simultaneously filled under slight pressure from the bottom up. Cold circuit = thermostat closed - water pump, engine. Hot circuit = thermostat open - water pump, engine, radiator.

With a $6 pump, I was able to completely fill the cooling system without introducing any significant air. Working a cold car, barely spilling a drop, not attaching my mouth to the car, and being done within 15 minutes are a bonus as well. I have put 50 miles on the car with great results and hot heat blowing right off the bat.

With the amount of issues other people have seemed to have, I really recommend trying this "pump" method and maybe using the "ramp" method as needed to remove any more air.

Good luck!!!

[lennon]

i've never had much trouble bleeding the cooling system on my m20s. i just do the standard bleeding procedure. i guess i'm lucky...

[nando]

yeah, same here. never takes more than 10-15 minutes. open all the vents, fill coolant resivior (leave cap off), open bleed screw, rev engine, and keep filling until the overflow line starts filling the resivior. close bleed screw, cap it off, drive around and top off as neccesary.

[Balleristic31]

Bumping this because it is so helpful. Had an issue bleeding my car and I took a bit of compressed air to the hose Jim suggested blowing in and the coolant shot out after a big burp!

[bangn]

Only problem with doing this with the thermostat closed is you dont know how much pressure your'e putting into the cooling system. Ive had a customer put a garden hose into the rad in order to flush out his system. Ended up blowing a waterpump gasket. The system is only ment to run at 14.5psi under pressure.

Maybe it would be better to use a radiator pressure tool for leak searching, this way you get a dial gauge to make aure you're not at risk of putting in too much pressure

[bmwstudent]

i've never had much trouble bleeding the cooling system on my m20s. i just do the standard bleeding procedure. i guess i'm lucky...

THIS, but not lucky. Just able to follow directions proven to work time and time again.

[shadowbethesda]

Bump... Because this pump method is the easiest way to do it. I tried everything else and could not get the system to push air out of the air bleeder valve. Really this should be a sticky. Car was not on ramps, and there was hardly any mess.

[raudonis]

Ask any old mechanic and he will tell you the best way to fill cooling system on many engines is with radiator hoses disconnected from the engine - filling the radiator and engine separately, then connecting the bottom hose, continue filling antifreeze separately, then connecting the top hose and then pouring in the rest of the amount - 99% of the times you will NOT EVEN NEED bleeding.

Step by step dummie procedure for m20 is on page 99 of this book: http://www.amazon.com/BMW-E30-Series.../dp/1855206781

It is on many torrent sites if you are a cheap bastard...

[AwakenNoMore]

when i did my top end rebuild last year i had to do my first ever coolant bleed for this car. All i did in addition to the standard procedure is drill a small hole in the thermostat through the arrow, bled perfect the first time, no issues.

[TobyB]

Drilling the t- stat seems to have been the winner for me, too-
never had any problems after that, even when I was in a hurry
and not taking much care at it...
t

[Bullhead]

Any pics on the hole location drilled through the thermostat? And do you have to use a special antifreeze? I would like to try both procedures if I had trouble with the standard. Also check this out, this guy wasn't playing he put "on tap" anti freeze to his reservoir.

http://www.youtube.com/watch?v=rP2TcA3Bj3s

[dnguyen1963]

Here...

https://www.google.com/search?q=drilled+out+thermostat&rlz=1C1JUFK_enUS510US510&es_sm=93&source=lnms&tbm=isch&sa=X&ei=E78aVMDONIXygwSBmoCQCw&ved=0CAkQ_AUoAg&biw=1440&bih=785#facrc=_&imgdii=_&imgrc=nUhGVdkZzhTNEM%253A%3B_Lqw3HbHM38I3M%3Bhttp%253A%252F%252Fwww.georgenitta.com%252Fthumbs%252Fthermo2.jpg%3Bhttp%253A%252F%252Fwww.georgenitta.com%252Fthermo.htm%3B375%3B304

How difficult was that? If you know how to search YouTube, you can search Google too.