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E34 (1989 - 1995)

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Old 10-31-2012, 12:08 AM
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BMWFatherFigure BMWFatherFigure is offline
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Location: Perth, Western Australia
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Mein Auto: E23;E32;E34;E38;R50;R55
Just to be clear I use Castrol oils (grade dependent on vehicle) changed at half indicated intervals, genuine coolant and PBR (Australian brand) DOT4 brake fluid changed on BMW intervals. To paraphrase the article (no author) Behr radiators supplied in the USA are prone to AlPO4 (phosphate) coating on the radiator tubes, if the wrong coolant is used. The author also thinks that the standard radiator is on the small side across the range. The BMW coolant is termed G-48 (which means nothing to me; maybe some one else knows). Behr know AlPO4 is an insulator and will cause overheating problems. Brass is not affected. IMO radiator flush compounds do not seem capable of removing the AlPO4 coating. I GUESS that anything that will dissolve the coating will also dissolve the radiator with it, but that is a GUESS. Any chemists out there??
Good - Fast - Cheap: Pick any two.
E23 735i; E32 735iL; E34 535i; 2 X E38 735iL (Oxford Green and Alpine White); R50 Cooper; R55 Cooper Clubman. E38 Parts Car
E21 318i; E30 318i; E32 735iL; E34 535i; E38 730iL; E53 4.4i
I've just changed my wiper blades and now my reverse lights don't work. Should I change my fuel pump relay?
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Old 10-31-2012, 12:41 AM
robertobaggio20 robertobaggio20 is offline
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Join Date: Oct 2009
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AlPO4 is aluminium phosphate. Some investigative searching and deductive reason (surely not what I'm infamous for) brought me to the following potentially insightful article :


I believe most phosphates are too stable to be removed except by scrapping them off.

Cummins sells a hard core radiator flush. Perhaps it is time to check that out and see if they will sell it to the general public:


Last edited by robertobaggio20; 10-31-2012 at 12:42 AM.
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Old 10-31-2012, 11:07 AM
paperplane94 paperplane94 is offline
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Location: Los Angeles, CA
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Mein Auto: 1989 525i M20B25
Zerex G-05.

Buy the concentrate, mix it 50/50 with distilled. Perfect.
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