Timing belt & water pump change

[TomB]

Morning,

I need to do a timing belt change on my K series.  Just wondering about the water pump - I know its best practice to change on a tintop, but what about on my 7 which only does a couple of thousand miles a year? 

The pump is probably ~25-30000 miles old, it isn't leaking.  I've no idea whether its metal or plastic impellers and is probably as fitted by the factory.  Do I let sleeping dogs lie, or replace it and risk it not sealing, and not knowing about it until I refill the coolant possibly in the spring after a rebuild? 

Cheers
Tom 

[Geoff Brown]

Don't forget to consider changing the timing belt tensioner which is very important. The water pump on a low mileage engine will probably last through several belt changes.

Depending on the year of manufacture of the engine it is either a manually adjusted or an auto tensioner. I do believe the auto tensioner is an acceptable retro fit to all engines.

[SM25T]

Water pumps do suddenly leak ... maybe corrosion on shaft abrading seals. I would change it as a precaution at 30k miles. Do make sure new one has metal impeller as some pattern parts have plastic.

[Wrightpayne]

I always fit a new pump and manual tensioner - Oily recommends Gates timing belts. I also do the alternator belt too.

Forgot to add I fit the VVC belt which is 3mm wider, again on Oily’s advice. 

I’d post a link to the relevant thread with part numbers but this is now frowned upon. Just use JK’s excellent search work around and I’m sure you’ll find it!

Ian

[TomB]

Thanks for your thoughts. Id not forgotten the tensioner, mine is originally the manual VVC one which I think is preferred (at least by DVA), so thats on the list.  

[SLR No.77]

Tom, you should be too busy decorating to be messing with timing belts!

Stu.

[TomB]

Nah, not too much to do if you like beige    Anyway, Ive decorated the garage... 

[Silver Machine]

Last year I drained the coolant. Replaced hoses with silicone ones. New cam belt and tensioner, Changd oil etc. This was on a 20 year old K. Left the engine without coolant for about 2 months. On refilling all seemed ok  till i noticed a drip from the water pump. The seal had failed in the water pump. Mine was the original 1997 pump so perhaps the seals were not in too greater shape. However I think the problem was caused by leaving an old pump and its seals to dry out over 2 months. Car needed new pump and cam belt plus a few repeated hours work. In retrospect I would replace the pump when I change the cam belt next time.

[rj]

I'll second using Gates. I have just had a 3 months old Continental belt failing after just three trackdays. It had completely disintegrated, so now I can no longer brag about my long lasting K-series. 

As for the water pumps I find the later ones being crap China quality and will at any time re-use a low mileage pump if it has no signs of trouble. If then the engine starts leaking it's not the end of the world.

[Mechanical Moz]

The reason for changing the pump is the same reason for changing the tensioner pulley, because failure of the bearing will throw the belt off. 

You could argue that the bearings should only need replacing at the recommended mileage interval, rather than the time interval that usually applies to the belt at typical Caterham mileages, but no one will recommend you just change the belt and leave the original tensioner pulley on.  As the pump has at least two more potential modes of failure than the tensioner pulley then it makes sense to fit a new one.

[oilyhands]

As a point of order, you cannot retro fit the auto-tensioner in place of a manual, bore vice-versa as the mounting points on the head are different , your head would need drilling and tapping, the auto tensioner is the Devils work.. for various reasons, not least of which is the uneven surface of the pulley. If you replace the water pump ensure it has a metal impellor and a proper EVAP chamber.

Oily

[john milner]

Unlikely nowadays but if there is a serious chance of the engine being started with frozen coolant then a plastic impeller may be better as hopefully it would shear off before too much serious damage is done. Same goes for pump bearing failure and corrosion. It would be interesting to know more about plastic impellers failing for no good reason as I suspect that a well designed weak spot could be a good thing. Good plastic and junk would look the same to me so for now I would stick with metal.

[SM25T]

Hopefully the days of frozen coolant are long gone with modern coolant/antifreeze??

[oilyhands]

Not a good idea to fit a pump with plastic impellor, if one one vane goes it pretty soon wreaks havoc with the remainder which leaves you with just a spindle , a passport to massive overheating. The chances of damage from ice formations within the pump chamber are infinitesimally small, fit a metal impellor pump unless you want to run the risk of overheating. I have seen 5 engines wrecked so far through overheating with plastic impellor pumps, two through the impellor coming loose, the remaining  three with broken off vanes.

Oily

[TomB]

Thanks all. I had a plastic impellor pump on an old Audi A3; when the belt was changed there was only one blade left of the impellor! What the story with the EVAP chamber?  Is this standard on an OEM pump?  Will Redline know what Im talking about when I phone them up to order? 

[revilla]

The evaporation chamber as I understand it is basically a little drip tray that catches droplets of water that may leak through the pump seal and, being bolted to the engine and getting relatively warm, allows them to evaporate away harmlessly rather than contaminating the timing belt.

http://www.75ztcommunity.co.uk/gallery/willyheckaslike-a37/water-pump-k-series-m240.jpg

There has been quite a bit of discussion as to whether they are a good thing. The benefits are as stated above. The claimed drawbacks are that they can mask the onset of pump seal failure, meaning that you don't spot the early signs and change the pump before it fails catastrophically.

I've always preferred to have one.

There's a rubber plug in the end of the casting. The pillar bolt for the timing cover passes through this. On some aftermarket pumps this is a harder plastic rather than a softer rubber and the bolt can be too tight. Don't try to force the bolt through a tight hard plug or it will crack (ask me how I know!). If necessary, relieve the hole just a little just to let the bolt pass through.

[rj]

I've found that, if you hoon the car massively on trackdays, then even though doing a cool down lap, the engine will overheat when you are in the pit even if the engine is idling. For this reason I've added an electric water pump in series with the internal pump and a thermo switch in the water rail betweencyl 2&3 that kicks in at 80 degrees. Not only does this prevent the engine from overheating in the pit, it also prevents the meltdown if the pump fails as it simply kicks when something is too hot.

No issues since then. At all!

 

[tangomikeromeo]

If it’s that cold would anyone take the 7?

[rj]

I was out for a trackday in snow on the 28th October - when I fired up the engine the water was -2,

The car had been in the trailer overnight.

[oilyhands]

The engine isnt overheating, it is simply taking the excess heat from the exhaust and exhaust valves and putting it into the coolant where it belongs, so either a post-coital electric pump or hold the engine at around 1500RPM to circulate the coolant until the temperature falls or the heat will soak into the exhaust side of the head and will eventually soften.

Oily

[rj]

Isn't it kind of overheating when it blows out the water? I reckon most of the heat comes from the exhaust, but temp goes up and water out.1500 rpm didn't do it and I don't fancy having ot sit in the car for 5-10 mins to keep revs up. Hence the electrical pump. Since then no problems at all.

Next incarnation will be a drive by wire setup, so then it might be easier to keep up revs.

[oilyhands]

If you are blowing coolant out then there is another problem manifesting itself. Good to hear the post coital pump has helped.

Oily

[rj]

I don't think so: Three cooling down laps would sort it, has has the external water pump. The internal pump was new old stock, system has been flushed with no signs of any issues at all - etc etc etc.

On the circuit the temp is - and has always been - rock steady at 75 degrees. When entering the pit the temp started climbing, fan kicked in but the climbing continued until the temp passed 100 degrees. After fitting the remote pump, the temperature rises, at 80 degrees the pump kicks in, and the fan kicks in at 85 degrees, then it will be oscillating between fan kick in and kick off until it doesn't reach it anymore and the pump shuts off at 75 degrees.

I think it was simply an issue of not having enough flow to remove the heat when the engine was below some 2k.

Of course I've had a HGF or two (or more) in 15 odd years where there's been other issues than the flow issue, and I think the HGF has been provocated by the overheating issue in the pit.