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SDI water pump woes- most VW pumps...

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In case any of you have been following my major service since buying the SDI, I decided that while I had everything in pieces, I may as well change the water pump. Got a good deal from GSF (£15 delivered).

Anyhooo...

I was wondering why the belt wasn't running down the middle of the pulley. My first thought was that someone in the past decided to fit a unit from another engine like the 1.9, which might be very slightly different but good enough. I didn't think much more of it till it was out.

So I have changed enough genuine VW pumps now to conclude that they ALL eventually fail. And the pattern seems to be between 60 and 80,000 miles. Aftermarket ones are a lot better. Pics follow:

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So if you have a belt that isn't running true, or maybe the water level seems to be dropped very slowly in the reservoir, check the pump... :)

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Nice bit of info that, cheers!

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Plastic impellers also have their advantages. If the pump is driven by the cambelt and has a metal impeller, any freezing of the coolant (through a lack of maintenance) will cause the cambelt to break, whereas a plastic impeller will just shear off.

RAB

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What he said ^

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Plastic impellers also have their advantages. If the pump is driven by the cambelt and has a metal impeller, any freezing of the coolant (through a lack of maintenance) will cause the cambelt to break, whereas a plastic impeller will just shear off.

RAB

Yeah you're right. But, christ, by the time the coolent (water!) has frozen (and expanded inside the block/head), I'd say that a fair amount of damage has already been done by then. Core plugs get pushed out, headgaskets separate, seals blown out, radiators split, heaters split, thermostat damaged, plastic fittings cracked and of course the impellor goes.

The trouble that I've found even with really well maintained cars using the right G11/G12/13 whatever (flushed & changed every couple of years), is that the plastic bit begins to separate from the shaft of the pump. I've seen quite a few like that. And then there's that odd spring loaded seal. Why oh why did they opt for that when the good'ol way of doing it was simply with a bit of rubber. Seal goes, bearing starts to move, impellor contacts casting, cam belt gets pushed off-line, cam belt jumps or fails. Game over.

I do understand that a beautifully made plastic impellor will outperform the rough cast aluminium ones that everyone else now uses, but for longevity, I think it was a poor decision by the 'cooling team' in VW engineering. Don't even mention the plastic hose connectors and thermostat flanges that warp, twist and leak after just a few years with those stupid zinc flashed metal inserts that chemically react with the ali head. Hasn't anyone heard of electrolytic corrosion?!?!? I guess VW make cars to make money. Cast ali is way more expensive than plastic.

Anyone remember about 15 years ago VW were pumping that rubberised goop through all the coolent passages to coat the internal engine surfaces to prevent leaks.... And then when it started to crumble a few years later, all the galleries began to block and then hot spots and then major broken engine.......... the shame of it. All I can do is shake my head. Fortunately back to normal again now! :)

Sorry for the rant!

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If you have a cambelt driven water pump, the obvious thing to do is change the pump and the belt (and nearly everything else associated with the latter) at the same time! Anything else is another false economy.

RAB

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We ALWAYS recommend a waterpump at the same time as a cambelt for the obvious reason that the pump is driven by the belt, just makes sense really....

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We ALWAYS recommend a waterpump at the same time as a cambelt for the obvious reason that the pump is driven by the belt, just makes sense really....

And the tensioner.

The design of the tensioner lends itself to wearing out. The part inside the tensioner assembly which allows the bearing to swivel slightly rubs against the part that is fixed to the block (the spring keeping the position/tension about right). Over time, the belt sideways force causes the spherical 'hub' (or whatever you want to call it) to become conical. As soon as the pulley runs at an angle, the belt shifts off the centreline and rubs against the pulley rim, ripping apart the belt. I've seen a few like that now- I'm surprised that the tensioner design hasn't been changed. You can tell because the belt makes an almighty chirping/whirring noise when rubbing.

Before installing the tensioner, I usually spray white grease between the rubbing surfaces inside the assembly. It also makes life easier when setting the tension as the sliding action is smoother.

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