Hey guys, Just want an opinion regarding a waterpump replacement part for an E32, or for any Bimmir for that matter. I have a huge headache as I have been going back and forth on this matter with new research coming in. I may be over analyzing but... I prefer to install OE Genuine BMW parts, Yes they are expensive but you pay for what you get..Quality. However in this case, I am not so sure. The genuine BMW waterpump is constructed from a plastic (or composite) impeller. The composite impellers tend to disintegrate overtime, causing the WP to fail and thus lead to overheating. I went to the local BMW dealer and had them reference the part. There have been no changes in part number, therefore, same part as factory installed and is therefore plastic/composite. I dont mind paying for quality, but if it's a design flaw, then shame on BMW for not fixing it with a metal impeller. The OEM parts (graf and geba) seem to have a metal impeller, which logically speaking, would fix the design flaw of the composite impeller disintegrating over time from heat and wear, etc. However, these cost roughly $45 to $55 compared to the genuine bmw's $200 or so. The issue with metal impellers is that they are heavier and may cause premature bearing failure. Even if it is not premature, the bearings in these fail and seize up the motor...........that is catastrophic. Just imagine the implications driving on the highway at high speed. <<<<--------------- dont want to be that guy. The Positive side of a composite or plastic impeller is that once it fails, the pieces disintegrate and the coolant leaks from the weep hole. Also, if you are vigilant you should see the temp gauge go up and you can turn off the engine. Again, at high speed on the highway this is not ideal. However, the impeller will or SHOULD fail before the bearing does. This will prevent the motor from seizing up. Maybe BMW was smarter than we all think and this was the point. I just dont like the idea of buying a cheap part and a cheap bearing is bad news. I would also like to point out that I have no problem doing preventative maintenance and either way I go, I would be comfortable changing the WP every 30k miles. 50K miles? to me $200 for a pump is cheap insurance. Point is, I dont want it to fail if it does and there goes my engine. Thanks guys!
The water pumps in M30's, M60's & M70's are all belt driven - if the water pump seizes, is it possible for that to result in the engine seizing? Are there reports of the belt tying itself into an immutable knot upon disintegration and locking up the engine with catastrophic results? If other online forums are any indication, isn't the consensus to avoid plastic-impeller water pumps like the plague? I would guess overheating upon failure might pose the bigger risk to the engine. The plastic impeller bits pushed through the cooling system I suspect are most disastrous to the radiator, although anything blocking cooling passages in the engine block and head would be a problem too. Related, but different issue - there are reports of fan blades failing, costing a hood, plus hoses, etc - replacing the fan blade is also cheap insurance, at least for M60's, and probably not a bad idea on M70's or M30's either. Design flaw? Probably just a cost-cutting move with unintended negative consequences - nobody talked about catastrophic plastic impeller failure prior to their introduction. The plastics used in BMW's starting around the very late 80's and early 90's continuing to today do not appear to be aging well - getting brittle with age, causing any variety of failures. The plastic impeller problem showed up relatively quickly, likely due to the harsh environment and high temps. Fan blade failures, sunroof clip failures resulting in expensive sunroof 'cassette' breakage, and more. Me, I'd go for a water pump as similar to metal-impeller water pumps of yore as possible. E36's presented a large enough market for someone to address it - other models are out of luck though: http://www.stewartcomponents.net/Merchant2/merchant.mvc?Screen=CTGY&Category_Code=BMWHPWP Not being able to get that for an E32, I'd get as close as possible, and would shy away from plastic-impeller pumps on the rationale that someone went to the trouble to make their own with a metal impeller instead of a plastic one. Sometimes, BMW OEM is preferable, but other times, other alternatives are just as good, or superior, or the same, but less expensive. There are Bosch parts that are the same, less expensive, and only lack a little BMW roundel emblem molded into it, for instance. With the prices you're talking, I'm guessing your engine's an M30, looks like you can get either type aftermarket - http://www.autohausaz.com/search/pr...990&cid=16@Cooling System&gid=2208@Water Pump Searching for E32 740i water pumps, both brands say metal impeller - if the BMW oem one used a composite impeller (which I don't know offhand), it's worth noting that they only offer metal-impeller pumps; might be worth checking if other sources specifically note metal vs. composite impeller.
Thanks for the input MGarrison! I guess if the waterpump fails, whether it is a composite or metal impeller, is bad news. That's why I'm a fan of preventative maintenance. And yes, I plan on replacing the fan clutch as well as it is about time to do so. I've checked over 5 others forums regarding this issue (roadfly, bimmirworld, audizine, VW, etc) and yes the consensus is that you go with the metal impeller. But I've read of so many failing to due premature failure of the bearing. This was extremely prevalent in the GEBA products so i would say stay away from that junk. Although, it is made in Germany which would suggest a higher quality part than Chinese or Mexican Junk. In one of the posts, it stated that the GRAF was spot welded but everyone seems to confirm that it is still an excellent part and although it looks less heavy duty than the GEBA, it actually feels like a quality part in your hand.. Probably will get one of those. I would prefer to get an OE genuine BMW part, and I would if there was a change in part #, but due to the lack thereof, that suggests the plastic has not been "upgraded" to newer and better composite impellers used in brand new, or newer BMW's. I just tend to favor quality, reliability, and originality. Based on what I've read, the metal impellers tend to expand during heavy loads and high temperatures, which would somewhat limit the amount of fluid circulating. I think that’s why BMW went with the plastic impellers since high temps do not affect it. Yes, I looked at those Stewart BMW high performance but none was available for an E32 735i. Kinda disappointed. Made in the U S of A and really heavy duty. dang it. And a side note on the Bosch water pumps.... I just bought one for my Dodge Dakota pickup and guess what....Made in China.....probably the most disappointing event that day when I opened the box. That is a shame.
The M30 engine in it's basic form was around for such a long time, I wonder when any of them were fitted with plastic-impeller pumps, or if plastic impellers being available now on some aftermarket pumps is just a result of them being used in later, other engines. In any case, metal impeller, yes. Fan clutch can't hurt, although those can be reasonably long-lived; I was talking about the fan blade, of which there are some pictures folks have shared of the aftermath (hood shrapnelled, etc) on some of the other online forums. I hadn't heard of this being an issue for M30 engines, with there being some speculation about higher temps being an issue for the fan blade plastics, & that M30 fan blades weren't seeing similar temp extremes (not sure of accuracy of that supposition, but recall reading that in a thread elsewhere), or just a change in the plastic formulations being used and being a problem later. Suit yourself of course, fan blades aren't too expensive, but I can't say I've heard of them self-destructing being an issue for M30's. I agree, there's no doubt to the efficacy of preventive maintenance, and naturally, quality and reliability is desired, which original BMW teile, in theory, should assure - we've had some 30-40 years of marketing doing it's best to convince us of that; but, yes, if the factory part is inherently flawed and never fixed, then other options or pre-emptive replacement may be the only solution. Disappointing to think you're getting a German part and find it's Chinese - a by-product of global economy and competitiveness I suppose; we'll have to rely on the hope that quality control, from wherever, is all it ought to be. Good luck with the project whenever you get to it!
