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-   -   Bleeding cooling system...do not overfill... (https://xoutpost.com/bmw-sav-forums/x5-e53-forum/105049-bleeding-cooling-system-do-not-overfill.html)

cn90 11-12-2016 11:22 PM

The bleed procedure as published by BMW is for a dry fill from factory when they need to prime the secondary water pump etc.

For routine bleeding, such as after cooling overhaul (WP replacement etc.), I just do simple things:

1. Engine Cold and Off.

2. Open bleeder screw near the tstat (remove it but don't lose it).

3. Fill the reservoir with the 50-50 mixture until it is 1" above KALT or roughly about 2" from the rim. Now, be patient! It is a slow process and coolant will flow out of the bleeder hole.

4. Re-install the bleeder screw (just snug it, don't force it!), then make sure coolant is still about 2" from the reservoir rim.
Replace the cap.

Now go for a test drive in the neighborhood with heat on etc., drive until the engine is hot.
Then go back home, park the SUV.
Wait 1-2 hours, then check coolant level, it should settle down to MAX area.

I have done this trick many times (overfill just a tiny above KALT when COLD) and it works. Very very easy.

CrazyOneToo 03-02-2019 02:37 PM

Hi all....

The day before yesterday my coolant looked a little low so I added some. Then after driving to work something
went sideways. On my drive home from work my check coolant message came up. I live near my work so
I drove home with a close eye on the temp gage. When I checked the bleeder screw I found the top had broken off.
I took the hose off to make it easier to work on and it was a PITA to get the broken part out of the hole but I did finally.
I don't really think I over tightened the bleeder screw but it is possible.
Luckily I had one in my old used parts box.

I saw somewhere that if you overfill the ET what isn't needed in the system will push out of the ET cap.

Did I overfill the ET? Thoughts????


:

jcp240z 03-03-2019 12:38 AM

If you overfill the pressure will build to either lift the 2bar (29psi) cap or burst / break something. An older system will typically have a part failure before the cap lifts. Many install a 1.2bar (17psi) cap. Better to slightly under fill than overfill.
A 50/50 glycol mix at 1.2bar has a boiling point of 270F. A 50/50 glycol mix at 2 bar is about 295F ( couldn’t find the exact number so used the estimate of 3F/psi from 280F@24psi)

X5only 03-03-2019 01:07 AM

Quote:

Originally Posted by jcp240z (Post 1156453)
If you overfill the pressure will build to either lift the 2bar (29psi) cap or burst / break something. An older system will typically have a part failure before the cap lifts. Many install a 1.2bar (17psi) cap. Better to slightly under fill than overfill.

Where would one buy a 1.2bar cap that fits our reservoir?

SlickGT1 03-03-2019 10:34 AM

I’ve been using an e30 1.4 bar cap for 5 years now. I feel way safer with it. The only retarded car in the world with a hose / expansion tank / radiator / valley pan exploding 2 bar cap.

CrazyOneToo 03-03-2019 11:37 AM

Quote:

Originally Posted by jcp240z (Post 1156453)
If you overfill the pressure will build to either lift the 2bar (29psi) cap or burst / break something. An older system will typically have a part failure before the cap lifts. Many install a 1.2bar (17psi) cap. Better to slightly under fill than overfill.
A 50/50 glycol mix at 1.2bar has a boiling point of 270F. A 50/50 glycol mix at 2 bar is about 295F ( couldn’t find the exact number so used the estimate of 3F/psi from 280F@24psi)

So I guess I'll fill it up and then siphon some out so the level gage reads right. I believe I did that last time I had to fill it up. I don't want replace the ET just because of overfilling. Thank you.

X5only 03-05-2019 11:02 PM

2 Attachment(s)
Quote:

Originally Posted by SlickGT1 (Post 1156461)
I’ve been using an e30 1.4 bar cap for 5 years now. I feel way safer with it. The only retarded car in the world with a hose / expansion tank / radiator / valley pan exploding 2 bar cap.

Cool, thanks for the pointer! Got it from dealer for only $17.


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