In Reply to: More Q's, Andy posted by Adnan on January 06, 2000 at 18:11:25:
I've done this job on both my 1991 model 535i and 1987 model 535 within the last 6 months.
I am a great believer in doing the whole coolant system. That means all hoses, new water pump, new thermostat, new seal for the block drain plug, new seal kit or completely new heater valve, and finally a new radiator. Yes, I said radiator.
My 1991 had a sudden failure of the upper radiator hose nozzle. The plastic on the side tank just cracked off. I have experienced this in the past, so to consider any radiator reliable for trips etc. it should be replaced at 8 years or more in service. Interestingly enough I have broken off the side tanks of the radiators I have replaced and the crossflow tubing was quite clean with very little obstruction. It's just hard to trust the plastic with age.
I also recommend using the BMW coolant. I believe it performs quite well and if you get any small leaks the blue color really shows up on hoses or other components.
I found that on both cars the upper radiator hose nozzle that is attached to the head had extensive corrosion buildup and damage. After I removed the corrosion from the nozzle, I found pin hole pits in the nozzle. Yes, some of the holes would be covered with the clamped hose but I have also experienced leaks through the pin holes. I highly recommend you examine the aluminum nozzles coming off of the component that is bolted to the front of the head. The bolt on replacement piece is about $45 and well worth it for longterm piece of mind. Also take a close look at the aluminum nozzle on the thermostat cover housing.
In regard to the heater valve there is a seal kit that runs $30 but most dealerships don't carry it. The complete heater valve assembly is about $75. Once again I don't care to open up the coolant system for a long time so I replaced the heater valve.
As concerns your question on threading the heater hose down the side of the engine, I broke off the plastic retaining clips. Given the age the plastic is just too brittle to successfully remove and reinstall. The lower half of the clip that is bolted to the block remained intact so I just laid the hose in the lower part of the clip.
In regard to the water pump and the use of gasket compound, if you can get ALL of the old material and sealant off of the block you don't need sealant. But if the block face is a little rough or slightly pitted i would go with some Permatex #2 on the block face. I used a wire brush on a drill to clean off the block face. A Dremel tool with a wire brush comes in handy. Get some spray on gasket contact sealant that acts like glue to stick on the paper gasket to the water pump. With the gasket held onto the pump, it is easy to install onto the block.
Be sure to get new bolts for the water pump to replace any of the bolts that are corroded. It has been my experience that you should replace all of the bolts. Unfortunately the dealer doesn't always carry a supply of the right size. Hopefully you can get some.
Well, seems like a lot of work. Overall cost of part should run you about $600 with a new radiator included. But you should have real peace of mind. You know what can happen to a head if you have a rapid loss of coolant at highway speeds and you don't notice it? The '87 is my 16 year old daughter's car. I just didn't have confidence that if she had a coolant leak she would be wise enough to stop the engine before the head warpped.