I had the cambelt on my 2004 WRX changed at a dealer back in the summer of 2013 with the mileage at 80,000 miles approx. I bought the parts myself and got the dealer to fit them. I got a kit from import car parts with a Gates belt and all the idlers, tensioner and new bolts.

I haven’t really used the car much in recent years. It is now on 106,000 approx and I realized that because it is now 7 years I ought to be replacing the cambelt again. I have the time to do the work myself now but have two questions:

1. Should I now just replace the belt or should I still be getting a full kit as before?

2. The water pump hasn’t been replaced ever as far as I know. I actually bought one back in 2013 but didn’t get it fitted at the last cambelt change due to the labour cost quoted. Should I replace the water pump now when doing the cambelt or is it best to leave it alone if it is working ok?

 

Can't really understand the labour cost part but as for idlers by rights yes but due to the mileage covered check them and make sure their ok no dry bearings or rumbling and you should be ok. I much prefer the water pump with the cast impeller.

 

I personally would be doing idlers as well. If your in there anyway and your doing it yourself, have the time why not? You could check them over and they could appear fine, give it X amount of time and you start to hear the odd noise then you are potentially going to start worrying that one is about to let go with devastating consequences. Seems like a false economy for me. It’s a relatively small price to pay in comparison to things going wrong. So why revisit it at a later date when you can do the job right first time?

Totally agree with time v mileage argument. But as with the water pump point it seems odd not to just do it, reduce future worry and future proof it regardless.

Bit of a throw away comment I know but some garages simply won’t drive a car onto their ramps if they are concerned these items are too worn, noisy etc as they refuse to liable themselves by doing so and the costs incurred in fixing shafted engines.

Everyone has an opinion on these things I guess.

 

Tricky...depends on the brand of bearings used in the idlers; Gates don’t make bearings. I always used to use Blue print idlers/tensioners which usually turned out to be NSK and bought the Gates belt separate. I don’t know what Gates kits use...and it can vary.

If they are SKF, NTN, NSK or any other Japanese or Euro brand and they aren’t dry I’d leave them ‘till the next belt change.

Water pump is a similar story...the bearing make and impeller design are details worth looking at...some metal ones are just bent metal blades with no curves so prone to cavitation, others are cast with curved blades. All badly made ones can spin and become loose on the shaft...just like the plastic ones. There’s a lot of junk being sold by the likes of €uro car parts etc.

 

Thanks for the replies. I guess it is a full cambelt kit then and also do the water pump. The labour issue back in 2013 was because the dealer wanted almost the same again in labour to do the water pump as well I think.

The water pump that I have already, that was supplied by import car parts, is the brand Aisin. It has the word Japan on the casting but has the bent metal impeller blades as mentioned above not cast. It is brand new in packaging. Is this adequate or do I need to be looking at buying another with cast impeller?

Can anyone recommend a good place to buy the cambelt kit please? Also what actual belt do people think is best to get with these kits as different places use different ones. I thought that Gates was the better brand and Dayco not quite as good?

 

There’s debate on the cast vs bent impellers as the dealer supplied Subaru branded pumps (and possibly factory) switched from cast to bent impellers on some models.

So the latter is ok. It’ll work and unless you go on tracks or running big BHP I doubt you’d notice.

But it isn’t as good; It won’t flow as much as the blades create more turbulence hence cavitation. Plastic and cast impellers have a nice curve to each blade and a disc on the top and bottom to guide/force the coolant to the outer edge of the housing; Even central heating pumps are made this way, because it’s more effective. Negative aspect is as it flows more it needs a tad more power, so tiny bit more strain on the belt and a fraction less BHP at the flywheel...but it’s tiny to the point of being barely measurable.

Most original pumps on other makes of cars I’ve removed are usually cast or plastic curved impellers. The cheap replacements have almost always been bent metal with straight blades. Obviously the latter is cheaper and easier to make.

Thing is if it’s using a cheaper impeller then its probably using a cheaper bearing too. Cheap bearings aren’t always packed with enough grease or use cheaper greases and use softer metals etc. As well as whatever method they use to attach the impeller to the shaft.

But Aisin is usually a good brand so it should be fine.

 

Thank you for such a detailed and helpfull explanation of water pumps. I had no idea about the different types of quality ones available. You have Made me want to buy a better water pump for when doing my cambelt.

Do you have any opinion on the brands of cambelt and where to buy from?