'90 535i Heater core installation question

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Originally Posted by ryan roopnarine

it took under 6 hours, 2.1/4 to get in, 3.x to be careful getting out using roadfly. bentley doesn't tell you the position of every single screw, nut, procedure to finagle things out, but the roadfly one does. i would tell anyone not to bother with the other instructions on the web or bentley unless you want to remove more of your dash to get in and make other repairs. if patrick tells you that, and the etk says until 1/90, i guess i'm mistaken with how late that change took place.

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Well, I told Patrick of my car's 3/90 production date, and he said BMW054514 is the correct part number, and described it as having 3 alu. tubes and 3 O-rings, rather than the more complicated setup and parts shown in your posted picture.

So, we'll see what shows up tomorrow or Saturday, and if it fits the car. With my luck, it probably won't. Hence all the pesky questions about how and what works for HC replacement. If I have to do this, I hope it's only once.

If the wrong part comes, we may be talking JB Weld and coolant hose. GRRRR.

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Originally Posted by myles

I did this a couple of months ago. I replaced the plastic pipes with new ones. I didn't find the job that hard. I had the heater core and the aluminum pipes removed and then reassembled it all in the car. I think it would have been much harder to assemble it out of the car and try to install the assembled unit in situ.

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Myles, bbig119, and Ryan, thanks very much for your insights.

Questions: Assuming the 3 old tubes are aluminum and can be left on the car and re-used, would there be any need to remove the radio and OBC, knee panel under the steering wheel, glove box, etc.?

To just replace the heater core itself, would it work to just remove the rear and front center consoles; the HC temp sensors; rear air distribution tube; and the heater housing cover? From various pictures on Roadfly and on Bentley page 640-4, it appears that the two heater pipe mounting bolts are accessible, making replacement of the HC possible.

To remove the heater housing clips, is it necessary to remove the glove box and under-steering wheel knee panel?

To take the centre console out you need to remove the glove box. Its just the way the parts all fit together. You can leave the panel above the pedals there, you just need to undo a couple of screws so that the console is not connected to it.

Keep in mind that my car is RHD and from what I can see in photos of LHD cars BMW made some changes in the way the console fits together for RHD cars. BTW - LHD looks a lot neater. I wish they mirrored the LHD design, but they didn't.

I believe you need to take out the OBC and radio. It will certainly get you some extra work room if you don't, and any extra work room in this job is useful. Removing the OBC/radio is so easy I can't see a reason not to do it.

The write-up posted on roadfly is very useful and if you follow that, you'll get to the heater core without problems. Take pictures as frequently as possible and label everything. Its very easy to forget where a screw goes, or even lose it at together.

Its not difficult getting to the heater core. Its only slightly tricky to get the new one in place. Its just a total bitch(or was in my case) to get the pipes with new gaskets installed far enough into the core to allow the aluminum lock to fit in place.

Good luck

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Originally Posted by bbig119

...Its not difficult getting to the heater core. Its only slightly tricky to get the new one in place. Its just a total bitch(or was in my case) to get the pipes with new gaskets installed far enough into the core to allow the aluminum lock to fit in place...

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Well, got it done today, mostly per Bentley. Removed rear and front consoles, radio/heater/AC control panel, and knee panel under the steering wheel. After disconnecting the plugs and cables at its rear, I folded the entire radio/AC/heater panel upside down/backwards and rested it on the open glove box lid. Took digital pics to keep straight what went where.

I did not disconnect the 3 hoses at the firewall, but rather put down a rag to absorb any spillage from the old HC. Then used a shop vac to suck any spillable coolant from the three old HC fittings, so when I pulled the HC out of the housing, it was not full and did not spill.

Fitting the new HC was easy: The left side collar was useful to seat the two alu. tubes with O-rings into place. For this, used long needlenose pliers to squeeze the collar up against the nylon housing of the HC, pushing the alu. tubes into proper seating and enabling rotation of the collar down into the locked position for insertion of the locking bolt, which I Lock-tited.

The biggest problem was re-fitting the rear part of the HC housing, as neither of the upper corners seemed to want to seat. The little silver clamps fit into grooves on one side of the housing, then simply push into place IF the housing shells are properly seated. Bentley shows a couple more clamps than my car actually has places for.

I started up the car to see if everything worked properly, but had defroster heat only on the left side. Messed around with this until I got a hunch, then tapped the accelerator pedal to goose the rpm, whereupon got proper heat from all all ducts and all heater settings. There was cavitation in the system, since the new HC went in empty, but all was well after gunning the engine once or twice, and topping off coolant at the reservoir. Bleeding the coolant system with the nose parked on an up slant would probably have prevented the cavitation.

While in there, I wish I'd done more to clean the HC housing than just wiping it out with a soapy rag, as there is still some stale coolant smell from the ductwork. My plan is to vacuum a string through each of the various ducts, then tie it to a soft wet sponge or cloth and draw it through each duct, to sop up and clean out the dried coolant. Anybody tried this, or done duct cleaning? How about spraying some disinfectant in there, or using long bottle brushes, etc.. to scrub the ducts?

Congrats on getting this done. Sounds like you did it without too much trouble. Your idea about the ducts sounds interesting, but I'm of not help here-- never tried it.