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JAM172

E12 M535i

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Can anyone please recommend the best method and flushing agent required for my e12 M535i, it sat for 17 years prior to restoration and has a wildly fluctuating temperature gauge, all hoses, stat and water pump have been replaced. Higher revs brings the temperature back down again, but it can get 3/4 of the way up. The radiator has been professionally rebuilt as well, but the likelihood is that it has silt & corrosion in the heater and/or water jacket. I don't think it is an air lock as the heater etc works fine.

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Not sure i've ever heard of a flushing agent for the coolant system but i believe the trick is to back flush ie use a hose and force water round the other way till it runs clear.

 

Did this on my saab and loads of crud and rust came out.

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You have never heard of Rad flush, or Bars flush??

When you say the other way, where do I place the hose on the engine side, the rad is all new? it will need to go through the engine water ways & heater,

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Now you mention it.... though not sure I've used them maybe I did it was long ago!

I'd avoid the rad as you don't want anything getting in there but the water comes in at the bottom of the rad (I think) so I'd be aiming the hose into that pipe.

I think it's more a case of trying to flush any crap out any way you can so probably worth doing in both directions.

Sent from my iPhone using Tapatalk

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19 hours ago, duncan-uk said:

Now you mention it.... though not sure I've used them maybe I did it was long ago!

I'd avoid the rad as you don't want anything getting in there but the water comes in at the bottom of the rad (I think) so I'd be aiming the hose into that pipe.

I think it's more a case of trying to flush any crap out any way you can so probably worth doing in both directions.

Sent from my iPhone using Tapatalk

Ok, thanks, so should I remove the thermostat 1st, blast water through the heater inlet/outlet hoses at the bulkhead, and also remove the engine coolant drain plug?

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I didn't but I'd guess the more access you get and the more points you can get the hose in the more chance you have of clearing the sediment.

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Not a new one no, but a "known" good one, I suppose that could be worth a try, but I don't think the symptoms match, it does not really get that hot idling (No airflow) more when ambling along 40-50MPH but not revving hard?

 

Edit: come to think of it, viscous is definitely not the issue, because I had to change from the earlier pump type, and it had the same issue with at and the original fan clutch.

Edited by JAM172

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You got the right stat in it? Remember I has similar problems with mine and turned out to be the incorrect stat for the car even though it was from BMW.

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Unlikely to be heater matrix as if blocked you'd get poor or no heat. Back to basics, How's the ign timing? Are the top and bottom hoses roughly the same temp at normal operating temperature indicating correct circulation, the bypass hose to the header tank must be clear.  Mixture?  It's been sitting donkeys so injectors could be below par and lean, also fuel pressure is very important on all M30's.

 

Go with the back flush first as really old antifreeze tends to congeal, reducing flow. Ultimately though you may find the HG Is ever so slightly compromised. I had the same scenario many years ago and it turn out to be HG due to an incorrect item being fitted previously. M90's were perhaps the least durable of the pre motronic (e28) M30's due to the larger bore size so could be a factor.

 

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On ‎02‎/‎12‎/‎2016 at 11:47 PM, FIVE-OH said:

Unlikely to be heater matrix as if blocked you'd get poor or no heat. Back to basics, How's the ign timing? Are the top and bottom hoses roughly the same temp at normal operating temperature indicating correct circulation, the bypass hose to the header tank must be clear.  Mixture?  It's been sitting donkeys so injectors could be below par and lean, also fuel pressure is very important on all M30's.

 

Go with the back flush first as really old antifreeze tends to congeal, reducing flow. Ultimately though you may find the HG Is ever so slightly compromised. I had the same scenario many years ago and it turn out to be HG due to an incorrect item being fitted previously. M90's were perhaps the least durable of the pre motronic (e28) M30's due to the larger bore size so could be a factor.

 

Thanks for your thoughts on this:

Heater works efficiently, in fact very hot.

Ignition timing is spot on.

Hoses feel even temp at "normal" operating temperature.

By pass hose is new, but I will check that it is clear.

Replaced the coolant, but there could still be silt/corrosion

I have a mate with a head gasket pressure/dye tester and all good.

The fuel pressure regulator is new, all fuel pipes have been replaced.

It goes like a train, so not sure about injectors, although I see where you are coming from, Can anyone recommend a tank fed injector cleaner?

 

My money is still on a dodgy stat, I think that hopefully it is a combination of the and flushing required, either way it is going to have to wait now, as the BARS flush I have requires that it is in the system and driven over a couple of days, it is currently SORN.

Edited by JAM172

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Apologies for the late reply, I've been having snags getting on the site as it's been painfully slow?

 

Given what you have said my money would be on the stat too, I've changed two in recent months on old BM's (not M30's but still) with very similar symptoms although neither car started to get too hot, just that as soon as the cars got up to speed in traffic the temp would wander off down to a 1/4 and then fluctuate. So maybe a combination of the flush and the stat will do it as long as you're sure about the fan.

As for in-tank injector cleaners, I've had success with Wynns additive although I did stuff it through in a much more concentrated fashion than the bottle suggested. Basically I put the bottle in with a 1/4 of a tank and gave it a proper Italian tune. Smoother running and butt dyno confirmation that it did something anyway. 

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Just pull the stat and see how it behaves. If all goes away and it runs cold you know that its the culprit

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