flushing the engine block

[expressfish]

Im refurbing my ol 325, tore it down , replaced all rubber, hoses, belts ect. The car was sitting for 5 years and the radiator fluid/ water mix was very rusty. I flushed the radiator w/ the garden hose and got just about all the rustly fluids out........is there something I should run thru the block or should I just flush it out with water and do a fluid change again after a couple miles of run time ??

[NC325iC]

flush it with water till its clean

[jlevie]

It would be best to be a bit more aggressive in cleaning the cooling system. There are commercial flush compounds that will do a good job of cleaning the system. The procedure I use is:

1) Get the front of the car 1-2' in the air on jack-stands.

2) Drain the coolant and remove the thermostat. Set the heater controls for
full hot.

3) Add flush compound and fill with plain water. Then run the engine at normal
temperature as specified by the flush manufacturer (usually about 15
minutes at operating temperature). In cooler weather it may be necessary to
block off some of the air into the radiator.

4) Allow the engine to cool until you can place your hand on the cylinder head
w/o discomfort. Drain the system and refill with plain water.

5) Run the engine for 10-15 minutes or until temp is close to normal.

6) Repeat (4) and (5) until the water drained from the system is clear and
free of debris.

7) Re-install the thermostat and fill with coolant.

Notes:

You need the thermostat out in order to have full flow through the radiator.
That will also make draining & filling faster and easier.

Always allow the engine to cool to the point that you can hold your hand on
the cylinder head without discomfort. That will prevent scalds from hot
coolant and prevent thermally shocking the head when you dump the coolant.

Filling the system with hot water makes the process go faster and keeps from
having to run the engine a lot in a cold condition (rich mixture).

[NC325iC]

youll never get to normal temp w/o a tstat

[expressfish]

cool, I just want to get all the rust out. After I yanked all the hoses and they dried out there was a film of powdery rust in all of them the next day, kinda like a coating. When I pulled the water pump there was buildup around the cylinder sleeve. I need to flush it for sure ! Thanks

[AndrewBird]

youll never get to normal temp w/o a tstat

If you block off air through the radiator you will.

[jlevie]

You can get normal engine temps (or close to it) w/o the thermostat in ambient temperatures of 70F and above. Colder than that it may be necessary to partially block air flow to the radiator.

[rodrigo]

Bringing this one back from the dead...

When re-filling the temp controls need to be full hot?

[E30_fiend]

^^^^^^
Yes

[jlevie]

As E30_fiend says, yep! But there's a bit more to it than just that. BMW's in general are not the easiest car's to bleed. The procedure that I use that pretty much works on all models is:

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.

[rodrigo]

thank you. :)

[wojtek79]

How much does this procedure change if I have the engine on an engine mount with no hoses attached to it at all? I also want to flush the block.

[JLegleiter]

How much does this procedure change if I have the engine on an engine mount with no hoses attached to it at all? I also want to flush the block.

Seriously?

[itsbrokeagain]

Seriously?

epic post of the year already.

[wojtek79]

epic post of the year already.

and I am still only a ..

I guess I was looking at it from the point of view that I would not be able to run the engine. I guess I'll just hook up the hose and go at it. Once I am done, pull the block drain plug and rotate the engine a few times slowly while on the stand.