Water Pump - Metal Impeller VS Plastic

[R4cup]

My car is currently off the road due to needing a water pump. I have already gone out & purchased a pump with metal Impeller but now im in 2 minds after reading a few threads.

Apparently although the metal ones last longer, if they do go (and they do) they take the whole block with them

I would like to know other members views on this?

 

[Big_daddy]

how can the metal one go R?

 

[GlanzaV]

Apparently the plastic impeller was designed to shear if the coolant froze (which it can do below -20degC) - if the coolant did freeze the impeller would shear rather than the timing belt snapping and destroying the top end.

Don't know how true that is though? Discussion welcome. I just know I parked up my LCR over christmas when it was -20deg C went to drive it a few days later and the pump had **** itself, car had only done 35k miles. So sounded plausible to me.

 

[Big_daddy]

has ever been to minues -20 in uk wel in the west midlands? whats the limit on our coolant the purple/pink (G*** something) befor eit freezes?

 

[R4cup]

how can the metal one go R?

Ive just heard they can snap

 

[Big_daddy]

Ive just heard they can snap

so how long is avaerage life span of a normal plastic one?

 

[AlexGSi2000]

Hmm, interesting.... My plastic impeller went in June last year, so was hardly -20c.

However, I would like to think the G12 coolant would prevent freezing, even down to -20c.

 

[R4cup]

so how long is avaerage life span of a normal plastic one?

Well my 1st pump which was replaced by the stealers about 2years ago has gone which i know was plastic but i do drive my car everyday & clock up over 12k per year.... has your pump ever gone At?

 

[Big_daddy]

Well my 1st pump which was replaced by the stealers about 2years ago has gone which i know was plastic but i do drive my car everyday & clock up over 12k per year.... has your pump ever gone At?

Not yet (touch wood it has on audi a3 T....

i just get metal one...it never freezes dat bad in uk espicvally were we live...just make sure u have right amount coolant in...in the winter u can increase coolant level a tad so its more conetrated ---it freezes minus -25 here ..lol

The G-12 coolant was designed specifically for all aluminium motors and I'm told that it should last the service life of the motor. G-12 is supposed to prevent freeze and corrosion damage, lime deposits and also raises the boiling temperature compared to G-11 coolant. Here are the specs for G-12 coolant: 

VW says the G-12 can be mixed at a minimum of "50 : 50" and a maximum of "70 : 30", "Coolant : Water" mix. Using a 15 lb pressure release cap.. 

50 : 50 (Coolant : Water) 
-37 degrees C to 129 degrees C 

60 : 40 
- 52 degrees C to 132 degrees C 

70 : 30 
-64 degrees C to 136 degrees C 

Coolant will always protect better than just water alone. As the VR6 in your car is the same as a 1995 Corrado I couldn't see why they wouldn't give you special dispencation. I think the VR6 runs hot enough and I think running water alone would make it worse. Although when running on a strip your car does spend a lot of time just sitting so this could help the temps. 

Hope this helps, Dennis

 

[-=Rob=-]

I replaced the water pump on my MK4 Ibiza TDi and was advised by an independant VAG specialist to go plastic impellor for the exact reasons above, if the metal one fails or breaks, it's expensive! I went plastic and have always had this on my past Seats...

 

[R4cup]

Thanks for the info Big D & Rob but i am right now lol
I have until the weekend to decide as thats when its going to get fixed

 

[kyle'87]

I spoke to a very good seat mechanic about them and he said that the metal ones can induce electrical currents (A bit like when you put two metals in a liquid and one metal errodes) and causing the system to malfunction.

Im always sticking to a plactic blade pump

 

[EZ Tutty]

I spoke to a very good seat mechanic about them and he said that the metal ones can induce electrical currents (A bit like when you put two metals in a liquid and one metal errodes) and causing the system to malfunction.

Im always sticking to a plactic blade pump

LOL!

Water pumps with metal impellors are fitted as standard to some 1.8T's anyway.... thats why there so readily avalible.

Yes there will likely be a tiny current produced, however it'll only be a few mV.... chances are you touching the car would induce more of an imbalance in the electronics... really not an issue.

and as for the freezing up thing... whilst possible, antifreeze which is replaced as required and mixed properly should protect down to -32*C.... not that the temperatures get that low in this country anyway.

Theres nothing wrong with using the metal impellor at all... altho equally theres nothing wrong with using the plastic one aslong as it's replaced along with every cambelt change.

 

[JB!]

i talked it through with my mechanic when i did min last year, he said go with SEAT's 2nd gen plastic blades, as he has replaced siezed metal ones.

tbh, its lose/lose.

just change it every 40k.

 

[tstrahonja]

I think plastic impelors are used so they will brake...
Bare in mind that factorys dont make money on selling the car but on the spare parts..therefore cars and parts are not made to last for a long time..VW almost gone bust when golf 1 was released...it was made too good, didnt brake a lot...
Same goes for some other parts...etc. duall mass flywheel wich is very expensive..and completely not needed on 1.8t...

 

[cletus]

R if your water pump was only replaced 2 years ago and you bought a genuine water pump then it will still be covered under warranty as all VAG parts have a 3 year warranty

 

[R4cup]

R if your water pump was only replaced 2 years ago and you bought a genuine water pump then it will still be covered under warranty as all VAG parts have a 3 year warranty

thats what i like to hear, seat supplied & fitted the pump so me & them once i get the knackered one off