The topic for today is going to be how to improve the reliability on your cooling system of your BMW 325, 328, 323 and US-Version M3 for the E36 Models. Some of the weaknesses these cars have is they are using plastic thermostat housings. They are using plastic pulleys throughout the system, water pump, power steering etcetera. And we're using plastic impellers on some of the water pumps.
Also, what you want to look for are the plastic coolant reservoirs on the radiators, they have a tendency to crack and the small bleeder screws that are associated with letting the air out, bleed screws for some of the thermostat housings, water hoses and a few of the coolant reservoir bottles.
So what we're going to do is we're going to review these items, and tell you how you can improve on them to make your vehicle more reliable. Here's one of the issues with the thermostat housings. Here is an original BMW Thermostat Housing, that's made out of plastic. You can see over the time that it has been in the vehicle, there's been leakage coming from the Profile Gasket leaking out of the unit, and there's been some leakage around the lower part of the Profile Gasket.
What typically happens here is as the plastic heat cycles several times, it has the tendency to warp this surface right here, and you can re-tighten and retort the bolts, you can re-tighten these bolts right here. Typically, what you're going to run into there if you over tighten them, they have a tendency to crack the flanges.
A good replacement unit would be to get an Aluminum Replacement Aftermarket Piece. It's much more durable. It's much more stable. It will resist heat cycling and if you do have a slight warpage or a leak at one point, you can take out the gasket, flat, file it or sand it a little bit on a flat surface and you'll get that surface back again. Aluminum is much more stable and it will definitely stop leaking.
Here is one of the biggest problems is Plastic-impeller water pumps. I don't recommend leaving this in your car at all. I don't know why these were invented, but it must be some kind of desire to sell water pumps. I have seen these impellers explode. I have seen pieces come off of them. I have seen them logged down inside of the engine block. What typically happens is the car will overheat on a slight basis and then slowly it will progress to a point where it's constantly overheating and you just never can figure it out, you'll replace the fan clutch or replace the thermostat and does another things, and it's very hard to diagnose when you're not prepared to have this car equipped with a plastic impeller.
Here is an example of another vehicle, this happens to be a Volkswagen pump, which has some of the same issues. They have a plastic impeller. And here this impeller has come completely loose. And this vehicle's problem or symptom was that the vehicle just slightly overheated around town and if you drove it on the highway, it would go under the rid continuously.
The cure for this is to purchase an Aftermarket Pump that uses an iron impeller which is what they've used for years, even BMW used them years ago, and this impeller will never come loose. It will be pressed onto the shaft, and it will stay there for many years. I have never seen one of these come off.
Now if you want to go above and beyond that, there are some high performance water pumps. This is the Stewart Water Pump, and this one is designed to flow water, have better flow characteristics, it has a larger bearing inside the housing, so this will support superchargers and things that put extra stress on the pulley assembly, and it's a stainless steel impeller that won't rust/corrode or anything. It's a little bit more money but this will probably be a lifetime pump for you.
Here is another thing you have to be careful of, plastic pulleys. These things have a tendency to crack, you'll get a little chips out of them, if you ever destroy a belt. What's going to end up happening, it will take a little chip out possibly. Any time you get a plastic pulley that has any kind of defects on the outside, you want to replace it. They are not that expensive.
Another thing that occurs is when you're taking the fan clutch off the vehicle, and you're using your holding tool, to hold the water pump, like this. If you put any kind of torque on those two bolts, you can fracture these holes, and you want to be very careful of that if you get any kind of fracture lines going through there. You want to replace the pulley, because if you get this thing mounted, and you feel good that it's on there okay, and there are some fracture lines underneath it, that pulley will end up coming apart on the highway somewhere, because there is a lot of stress and tension on it. So always replace plastic pulley.
So anytime there is a power steering pulley or any pulley that's made out of plastic, it's been on the car for 5-6 yeas. It's worth the investment just to get a new one. Here's a little item that's put a lot of cars into the leak zone here. And it's these little plastic bleeder screws that are on the thermostat housing of E39 Models, and they are also typically on the coolant tanks of some models, and they are just a screw that's designed for you to allow the air to escape when you're trying to bleed the system.
What happens with these little bleeder screws is as the plastic fatigues, their heads pop-off. So you can tighten them down, you snug them down actually. You've got to be careful how tight you get them, and you'll snug them down, and a day or so later after they have heat cycled once or twice that especially if this bleeder screw is older, it will have a tendency to do is pop the head right off of it. Once it popped the head off of it, you'll have a water leak all over.
What we've done is we've developed this Brass Bleeder Screw that replaces it, has no chance of the head coming off of it, and it eliminates one more chance of a leak somewhere.
Now another thing you want to look for on plastic coolant bottles. They have a tendency to crack at the weld seams, meaning where they are glued together. This one here exploded on this, and the vehicle just spewed out all the water, because what you're looking at is about 14 PSI of water pressure when the car is hot. And if you start driving it harder that water pressure will exceed that a little bit, and all of a sudden, it will burst open at the seams. This was not that old of a reservoir, it's probably only couple, three years old.
They also have a tendency to crack length wise on corner seams. They'll also have a tendency to sometimes strip out the small bleeder screw hole, you've got to watch that, and all of these little, tiny little bleeder, hose nipples and stuff, you want to watch them right at the edges there, they have a tendency to crack just from flexing and they'll have a tendency then to leak on you.
What you want to look for around the seams is look for any residue, any white residue running down the sides. That's tail-tail sign of any free stains that have been sitting there for a while. The same kind of stain that we have on this thermostat housing. All of this white stain that you see around here, all of this stuff is evidence of coolant leaking, that has dried up, so always look for that, because that's going to be what causes -- what you're going to be looking for in order to have to replace these things.
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