Coolant Bleed Question

[ElNormo]

So I've replaced my water pump and thermostat. Everything's back together. I've read all the good posts I can find about bleeding the coolant, and just got back from the garage after my first attempt. Admittedly, I'm still not sure what I'm doing .

We opened the bleed screw on the thermostat and began filling the tank. After about a gallon-and-a-half, the tank began to fill. The bleed screw didn't show any activity. I squeezed the upper radiator hose a few times, and heard air wheezing out the hole. Eventually I was able to get a few drops of coolant to shoot out, but never got a steady stream.

We fired up the engine with the tank cap open. After about 5 minutes, the coolant in the tank rose to the top, at which point we turned off the engine. The coolant immediately dropped back down.

So... what next? I thought the coolant expanded due to heat, but why didn't it drain out the bleed screw? And why did it drop down immediately after turning off the engine?

If it makes any different, the front of the car is still jacked up. It's a 535i, M30 engine.

Thanks for helping a newbie!

Norman

[Kibokojoe]

With the front of the car elevated just a little you should get a steady flow of coolant from the air bleed hose. Have you run that engine and it is overheating? Sometimes you have to run the engine a couple of time and bleed between runs. I have always elevated the front on ramps but only up a couple of inches. It has always worked for me. Is the return line from the fill tank to the radiator open?

[ElNormo]

With the front of the car elevated just a little you should get a steady flow of coolant from the air bleed hose. Have you run that engine and it is overheating?

No, we haven't let it run that long. I stopped when the coolant rose to the top of the reservoir valve. I didn't see it fill, so I'm not sure if the extra fluid came from the "refill" hose. But it dropped as soon as I turned off the engine.

When you say "from the air bleed hose"... are you disconnecting a hose to bleed the air? I'm just opening the bleed screw on the thermostat.

Thanks again,

Norman

[Kibokojoe]

No I am talking about the coolant return line that is on the left side of the engine compartment it runs between the filling tank and the radiator. Sometimes this line becomes clogged and doesn't let the coolant recirculate from the filling tank and the radiator. Mine was clogged. I took the filling tank off and cleaned out the line with compressed air. The orifices in the filling tank are not easy to clean. I used a small wire and ran clean water and compressed air until they opened up. It was amazing how much crud was lodged in those little holes. It was completely clogged. I also had my radiator flushed.

[Kibokojoe]

Run the engine and watch the temp dial. If it goes up to half your good but if it climbs beyond half you will need to bleed more air. It doesn't take long for the M30 to reach operating temp

[shogun]

http://www.nmia.com/~dgnrg/page_19.htm

[Kibokojoe]

Enough said

[ElNormo]

No I am talking about the coolant return line that is on the left side of the engine compartment it runs between the filling tank and the radiator. Sometimes this line becomes clogged

Just an update... I disconnected the return line from the radiator and blowed through it (I attached a plastic tube as to avoid ingesting coolant). The hole on the reservoir is not nearly as big as the picture shows, more like a pinhole. It takes quite a bit of force to send coolant through. Tomorrow I'll try blowing it out with an air compressor. If that doesn't help, I might take the hose off the reservoir and poke a nail through to see if I can break the hole open a little bit.

Thanks again,

Norman

[shogun]

I just "repaired" one on an Alpina B12 E32 last Saturday.
The molded plastic tube connection is sometimes partly blocked on the expansion tank from the production process of the expanison tank. Only just a little bit of liquid was coming out into the expansion tank. Then I used a bit thicker metal pin and cleaned this plastic connector inside and suddenly a nice stream was coming out of the return line, similar as shown in my link above on Gale's site.

[ElNormo]

The molded plastic tube connection is sometimes partly blocked on the expansion tank from the production process of the expanison tank.

That's exactly what's happening to me. I'll let you know tomorrow how things turn out.

Norman