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Coldswede wrote: If you want to go the acid flush after the detergent flush as Winfred mentions, I used citric acid crystals in mine and worked very well.

I haven't tried it, but I've heard very good things about citric acid. Supposedly it works well, but isn't too hard on things. A coworked told me the winerys all use it to clean things because it's food safe, but still strong enough to do some good.

Moosehead is right. flush he heater core. Also remove the block drain (under the bank 2 exhaust manifold) and t-stat. Flush water every direction you can possibly flush water. It wouldn't hurt to remove the radiator and reverse flush it up side down.

Not that the applications are similar, but the flathead Fords all came without the casting sand completely removed. There's naturally been a long-enduring war to remove same and all the rust/gup/sediment that's settled in there over the years and an approved fix is to run 2 gallons of white vinegar for a day, drain, examine, repeat until all clear.

Not sure about BMW aluminum castings, radiators and waterpump bearings, but....it's $2.

With the ignition ON, HVAC temp set full hot, the radiator cap off, and the block and radiator drain plugs removed ... shouldn't the coolant drain from the heater core?

Or does it require its own special step involving disconnecting the lines from the heater control valve and flushing the heater core seperately?

Jeremy

Jeremy wrote:With the ignition ON, HVAC temp set full hot, the radiator cap off, and the block and radiator drain plugs removed ... shouldn't the coolant drain from the heater core?

Or does it require its own special step involving disconnecting the lines from the heater control valve and flushing the heater core seperately?

Jeremy

No, I think you're going to need to run the engine with water in there and HVAC open to flush out the gunk in the heater core. Flushing with the block and radiator open isn't going to get back into the core.

Frybrid 524td wrote:No, I think you're going to need to run the engine with water in there and HVAC open to flush out the gunk in the heater core. Flushing with the block and radiator open isn't going to get back into the core.

I understand it won't really flush, but it should drain under those conditions and be reasonably (though not completely) empty, right?

No, because the inlet and outlet of the heater core are higher than the core itself.

mooseheadm5 wrote:No, because the inlet and outlet of the heater core are higher than the core itself.

I didn't know that. OK, so when I flush it, which is the inlet and which is the outlet so I can make sure to backflush it? Will it be obvious? I can't remember what things look like back there at the moment.

disconnect and apply garden hose to heater core

Sounds kinky.

mooseheadm5 wrote:No, because the inlet and outlet of the heater core are higher than the core itself.

bingo!! My method for cars like these is to take both heater hoses off and flush water back and forth until its clean. It seems like typically some of the sediment gets trapped when water flows one way. It'll look clean, but flowing water back the other way will produce a nice puff of sediment again. Same goes for the entire rest of the cooling system. You can take off the thermostat to flow water through the block. And when you think you got it all and everything flows clear, when the system heat cycles it will break some of the stubborn sediment free and tint the cooling system rusty brown again. I am describing some severe cases that I have seen, but your description sounds like it may fall into the "severe" category. Also, be careful putting pressure to the heater core from a garden hose, it is only designed for 15 psi, and heater cores are a fairly long job in these old hogs. if its not flowing freely, be careful how hard you force the water in...

My advice is (if you want to hear it) to not replace any of the hoses, or fill it with coolant, yet. but rinse it clean, fill it with water, drive it a few days, rinse it clean again. Repeat until it stops tinting the water brown. Then replace all of the hoses, especially the crunchy ones. The "crunchy hoses" description you mentioned is what leads me to believe that yours is severely corroded. I bet they are lined in solidified silty gunk, and the noise you are hearing is the crusty crap crunching when the hose changes shape.

winfred wrote:disconnect and apply garden hose to heater core

Beat me to it!

wkohler wrote:Sounds kinky.

Lucas_Roehr wrote:if its not flowing freely, be careful how hard you force the water in...