water pump replacement-should I or not?

fredo328 · 12-07-2004, 11:13 AM

I've pretty much prepped myself with all the DIYs and related threads to do this job blind-folded. Just as I was ready to move ahead with the job a couple of my buddies (one is a car dude-rebuilt a 65 Fastback, the other works in a garage) told me to wait until the thing started giving me problems before replacing it. Reasons given are: you'll have leaks that will be tough to find and fix, another was my timing belt will be thrown off. Coming from these two buds of mine was enough to give me pause and ask you guys what you think. Problems with leaks or timing belt after doing the job?
I have a 98 328 and have no idea whether the impeller is plastic or metal, no overheating problems and have 70,000 miles on it. I've read here that BMW changed over to metal in 98 so who knows.Thanks

kocio67 · 12-07-2004, 01:14 PM

If you have 328 you have 6 cylinder engine which does not have timing belt. It has timing chain which is not affected by changing water pump in any way. You will need to remove serpentine belt though which is not a big deal.
Leaks - if you use good quality parts and follow common sense should be no problem.
You will have to of course remove air from the system after pump replacment.

Jeron · Jeron's Garage

They changed to metal impellers in early 97 prodution cars I believe. But interstingly enough, now they back to placstic.

I wouldnt change the pump until it gives problems. Like kocio67 said the pump is not on the timing chain.

sjkemp · 12-08-2004, 04:46 PM

I agree with Jeron. I too thought they changed to metal in 97. If anyone knows different let us know. If you had a plastic impellor I would change it ASAP because of the risk of catastrophic failure. The metal ones should last for more than 100,000 miles. I would leave it alone until it shows signs of wear (leak or any play in the shaft).

Scott

LeRoux Strydom · 12-09-2004, 12:13 AM

If you have other reasons to get in there, replacing the water pump is a good insurance policy. The w/p on my wife's car (96 328i) failed at 145k km's (90k miles). I subsequently learned that BMW SA issued a service bulletin advising the replacement of water pump on these engines at 100k km's (60k miles). It is an easy job. Also replace the thermostat while you're in there.

LeRoux

dboyles · 12-09-2004, 12:39 PM

Quote:

Originally posted by Jeron
They changed to metal impellers in early 97 prodution cars I believe. But interstingly enough, now they back to placstic.

I thought the new ones were some sort of composite material that are supposed to be as reliable as the metal impeller ones. Is this not the case?

Jeron · Jeron's Garage

I would assume that the material has been improved but I doubt it is too high tech or they would just use good old fashioned metal. I always assumed that the first switch to plastic was for financial reasons. It's probably just better plastic.

"now they back to plastic" did I really write that garbage?

fredo328 · 12-09-2004, 04:53 PM

I read that bmw switched to metal (just dont know what year, I heard early 98) and then later switched back to a better composite/plastic becuase the metal ones caused some kind of damage to the bearings.

sayah · 12-12-2004, 01:40 AM

If it ain't broke, don't fix it!!!!

Watch for leaks, if you notice this condition, check the neck of the upper radiator plastic thingy to see if that needs to be replaced first.

BTW, in my humble opinion replacing hoses is often not necessary.

Just my 2 cents.

sjkemp · 12-13-2004, 12:01 PM

The first generation of plastic impellered water pumps get brittle with time. They then are prone to catastrophic failure which can cause not only loss of cooling but also impact of the fan blades into the radiator. I assume the new water pumps are constructed from a composite which retains it's strength.

Scott

DR.WA///M · 12-13-2004, 01:31 PM

I say do it and while you are at it might as well chang you thermostat and its housing, flush the coolant, spark plugs consider it a tune up and trust me its better replacing it now than later!

valenciacarrera · 12-15-2004, 02:39 PM

I used to work in Detroit and I am some what familer with the problem. My roommate works for a company who made the water pump. (A french company-go figures) The problem with plastic impeller is that it has different thermo expension property than metal shaft that it attaches to it. Basically, when the water pump heats up plastic stretches to different size than metal. The difference create stress and over time the impeller creates crack because of this stress. I usually lean on the side of "If it aint broken don't fix it." But for this particular problem the problem is not "IF" it will break rather "WHEN". So you can be proactive and fix it at comfort of your home or wait until it blows up on the road somewhere.

my $0.02 worth.