M30 cooling system bleeding.

General E28 FAQs.
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spinedocab
Posts: 2600
Joined: Feb 12, 2006 1:00 PM
Location: Upper Bucks County, PA

M30 cooling system bleeding.

Post by spinedocab »

There is a sure way to bleed the cooling system on 'big' six engines.
1. After repair is made (before adding coolant) remove bleeder screw and run
a small piece of wire down the hole to dislodge any mineral deposits..
2. Replace the screw, but leave valve 'open'.
3. Open heater control valve and add coolant until it begins to escape from
the bleeder hole.
4. Now close bleeder screw and replace the expansion tank cap and tighten.
5. Remove the small coolant line that runs from the radiator to the
expansion tank AT THE EXPANSION tank and hold it as high as you can.
6. Now attach another hose the expansion tank in place of the one you've
just removed. BLOW (gently!!) through this hose until coolant emerges from
the small elevated radiator hose.
7. Now remove the 'blow' hose and reconnect the small radiator hose to the
expansion tank..
8. Now top off the expansion tank to the full mark.
9. Start and warm up engine and check for leaks!!
That's it. Good luck.
BTW, this procedure is compliments of Jim Rowe at Metric Mechanic
Last edited by spinedocab on Nov 20, 2010 11:22 PM, edited 1 time in total.
Fuel
Posts: 632
Joined: Nov 20, 2008 12:09 PM
Location: Chattanooga, TN

Post by Fuel »

wkohler wrote: Just look at the fan. Then look back towards the car about 4". On the top of the thermostat, you'll see a bolt that uses an 8mm wrench. There's your bleeder.
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nutgone
Posts: 16
Joined: Sep 09, 2009 11:25 AM
Location: Bristol & East Sussex U.K.

Post by nutgone »

This also works for m20 engines, although I found it best to begin filling from the rad end of the top hose, if the system has been completely drained, this ensures the block gets filled from the bottom & means you can fill it slightly quicker. Blowing into the bottle with the bleed screw open can also help to shift the last little bits of air. Try not to ingest any antifreeze tho :roll:
spinedocab
Posts: 2600
Joined: Feb 12, 2006 1:00 PM
Location: Upper Bucks County, PA

Post by spinedocab »

greentalks43 wrote:I am bleeding my system tomorrow morning and I do not quite under stand the following:

6. Now attach another hose the expansion tank in place of the one you've
just removed. BLOW (gently!!) through this hose until coolant emerges from
the small elevated radiator hose.
7. Now remove the 'blow' hose and reconnect the small radiator hose to the
expansion tank..

Is the small elevated hose facing the firewall? Am I blowing into another hose attached to the expansion tank thats facing the radiator until coolant is coming out of the hose facing the firewall? Thank you!
This requires an accessory hose, not just the parts attached to the car in normal operation.

The "small elevated hose" is the one STILL ATTACHED TO THE RADIATOR, the other end of which you have just removed from the expansion tank. The hose you blow into is the extra one you brought along with which to do the job. It is attached at one end to the nipple on the expansion tank (from which you removed the end of the hose going directly to the small nipple on the radiator (and is now the "small elevated hose".

These are hoses. They point wherever you want them to, so I don't want to make reference to firewalls and other landmarks for the purpose of identifying things correctly. What they are attached to is more descriptive.

Keep the tank reasonably full of coolant and the cap ON. Follow the other instructions, and you should be fine.
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