Water pump GRAF or GMB

I installed the aluminum pump (Graf) on the wife's Tiguan and it has worked great since. Have put 40K miles on the metal pump and no issues.

GRAF makes this particular pump without the magnetic impeller, and it’s the best option.

Graf is good. They are an OEM (original equipment manufacturer)

GMB is a decent pump.

I run a Graf pump myself for about 2 months now and it's working fine so far.

In my case the leaking was from the plastic water pump housing which is a common fault for this engine. I replaced the plastic water pump with GRAF PA1359, which is metal housing instead of the OEM plastic one.

I've run the plastic pump on 2 different cars for over 100k no issue, in fact I only changed one because the thermostat went bad and the water pump's reputation. I do have the metal Graf pump now, I like it so far.

Melling and Aisin are both premium WPs. Airtex is pretty good. GMB is ok.

I replaced the water pump in 3/2021. By 2/2022, it started leaking, so I replaced it under warranty. It leaked again in 1/2023, leading to a 3rd replacement. Now, one month in, the new pump is already leaking, this is driving me insane. This will be my 4th replacement in the last 3 yrs! These are GRAF PUMPS.

My '89 325iX doesn't put out much heat at idle, but as soon as I rev it to 2000 rpm, the heat starts coming out of the vents. At idle it is around 65°F air and at 2000 rpm it goes up to around 95°F (it is ~35°F outside today). I noticed a whistling noise that seems to come from the water pump at idle. Once the car got to normal operating temperature, I noticed that at idle coolant stopped coming out of the bleed hole. If I revved the engine a bit, coolant would flow. I replaced the water pump (Graf) 2900 miles and 3.5 months ago. My intuition is that the water pump isn't generating sufficient pressure at idle to move the coolant through the heater core.