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From digest.v7.n198 Sat Aug 30 23:07:09 1997
From: "Chao, Harvey" <>
Date: 30 Aug 1997 21:17:13 -0700
Subject: Lssns Lrnd, E28 hi Temps (Long)

This got pretty long, if E28 running too warm problems aren't your = problem you may want to skip it.

Lessons learned regarding an '86 E28 eta running warm.

Compared to the earlier ('83) E28 I had, this one always seemed to run = warmer, and in particular on warm days when traffic bogged down or came = to long red lights and stop 'n go with the a/c running,-- it would heat = up to about the 2 o'clock position on the temperature gauge - and I was = nervous it might skyrocket on me. When traffic would finally start = moving, it would take several miles and or a very long time (compared to = the '83) to eventually cool down back to the 12 o'clock position.

Tried the cheap'n easy things first, made sure fan clutch was good, = flushed cooling system (stuff came out essentially clear), new = thermostat, and made sure belts were not slipping, added water wetter to = the new coolant. [Side note - I added water wetter to the car when I got = it and it helped the temperature some, and after the cooling system = flush, without water wetter it seemed to run warmer than with it before = the flush, so added it to the new coolant.] Still no help. I knew when = I bought the car that this was going to be an issue, because it ran warm = then, and there was a good film of brown "mung" inside the plastic = coolant bottle. I cleaned that out, and when no film came back to = replace it, I was hopeful that with fresh antifreeze in the system, = perhaps the problem had gone away (fool that I was).

Well the problem persisted and so this morning, having exhausted the = cheap and easy solutions, I replaced the radiator with another factory = oem Behr unit. Driving conditions and weather will tell in the coming = days if this fixes it.

By the way I priced radiators at 4 local sources in the SF Bay area and = got prices ranging from $272 =3D> $309 plus tax, with BMWCCA discount. I = also contacted two list mail order places. Although they both had the = same price (no tax, but add shipping), one was not an OEM Behr unit, and = although the other was, as I thought about shipping a large flat box = cross country, all I could think of was that "Murphy" is alive and well = and could almost count on getting the box with a "through hole" right in = the center of the radiator (so I'm paranoid- doesn't mean that "they" = aren't out to get me anyway! :-) ). Decided that rather than risking = the hassle of shipping damage and the attendant delays, although I really = would have liked to order from the East Coast OEM supplier that I = respect, I didn't want to risk the hassle and delay of possible shipping = damage (OK - call me "chicken"). Perhaps, I have reflected, that mail = order is best for things less fragile or vulnerable to damage. By the = way, the place that I did buy from invoiced the list price of the = radiator as $357.73 vs. the BMWCCA discounted price of $272 plus tax.

Being a masochist at heart, I was curious to see the state of the old = radiator. Having been told from multiple places, (radiator shops, = dealer, independents) that these aluminum radiators with crimped on = plastic tanks are "throw-away" and cannot be disassembled, rodded and = then re-assembled, and having already bought the new radiator, what have = I got to loose, and what can I learn if I try anyway? Well, using a = medium blade (1/4") screwdriver, I placed the blade between the plastic = tank and the "dimple" at each point along the sides, top and bottom of = the tank, twisted the blade at each dimple and simply bent the = surprisingly soft ductile aluminum metal (some aluminum alloys are very = hard and brittle) until the "dimple" cleared the edge of the tank - = basically this bent the crimped band of metal out and "down" from the = edge of the plastic tank. Although I have not bothered to try to = re-assemble it, I think that for any of you who are "financially = challenged enough, you may try this, it is a possible "can do" if you use = some kind of gasket "goo" between the old gasket and plastic tank flange, = and then use a large pair of arc joint or water pump pliers to bend the = crimps back in place, perhaps finishing up by tapping the original crimps = back with light taps from a hammer on a screwdriver handle with the blade = placed on the crimps (indentations). Let the goo set up overnight and = then pressure test. If it doesn't work, the worst is that you wasted = some time and still have to buy a new radiator.

When I took the tank off (The output side) the end of the radiator and = the inside of the now exposed end of the tank were well coated (about = 1/16" deep) with the brown "mung" that probably is a mixture of rust and = scum, particularly on the ends of the exposed tubes that run from the = input to output tanks across the width of the radiator. This was in = spite of recently thoroughly flushing the system with a chemical flush = and then rinsing both the system and the radiator together and separately,= in the normal circulatory direction and in reverse. While moist, this = stuff rinsed off very readily with the pressure of a stream of water from = a garden hose nozzle. But, when I used the hose to flush water through = the radiator from the remaining tank to the exposed end of the radiator, = although the water flowed freely enough to not generate any appreciable = back pressure at the hose, I was able to look at the flow through the = tubes of the radiator core and see that about 1/3 of them had no flow at = all! Most of these were along the front row of tubes, and were mostly in = the center of the radiator and towards the top (i.e. the bottom radiator = tubes were in fine condition). I tried to force water through the = individual clogged tubes using a regular garden nozzle and then a with a = high pressure "sweeper" nozzle - no dice. I then used a piece of piano = wire to try and "rod" the clogged tubes. With significant difficulty, I = was able to clear a few of the tubes that I tried. It was clear that = these tubes were seriously clogged - it took perhaps 5 minutes of up and = down with the wire held with pliers to eventually work it the length of = the tube, using a flow of water to flush the "mung" out as I worked.

My best conclusion is that one of (or both) of the two previous owners of = this car got careless and let the antifreeze deteriorate to the point = where rust started to occur and allowed it to clog the radiator (makes me = wonder about the state of the heater core now!). I think that next time = I flush the cooling system, I will probably go with the stronger flush = (the kind that requires a post flush neutralizer step) and see if I can't = work at cleaning the cooling system and heater core out more thoroughly.

Hope that some of you may benefit from this and that it wasn't a total = WOB!


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