JowettTalk

On Saturday I took out the water pump of the SC to repair the keyway that had worn. During removal I found the fan support was fractured and the thermostat had found its way up into the rubber pipe and was broken. Also the bearing had not been located with a circlip. OK the bearing had not moved and may have been as desired by the rebuilder, but I was not happy and have fitted a circlip. The casing also required a new helicoil as on removing the bolt the helicoil came out.

I first tried welding up the very worn slot, turned it down in the lathe and then tried milling out the slot. But the metal was too hard so I turned the shaft and milled out a new slot.
This pump had a sealed bearing and thus did not have the bearing cover or felt fitted. I am convinced the keyway issue was caused by the pulley not being tight on the bearing causing all the rotation force being taken by the keyway. Thus I am making sure the pulley clamps to the bearing and will add plastic metal to be absolutely sure the pulley and keyway cannot move. IMHO this should be a taper fit or at the very least the pulley should have a steel boss into which the keyway can locate. The small keyway face into aly is not enough to hold so much torque.

This was OCRed (Using Adobe Acrobat 9 Extended) from this month's Flat Four amazingly without any correction. I have left one (%= 1/2) error in so you can see what might occur.

WORKSHOP OBSERVATIONS
Vic Morrison
WATERPUMPS RE-VISiTED
There has been a few cases of premature failure of waterpumps after about a year since being fitted with new seals and bearings etc. so a closer look was needed. I had reconditioned the waterpump from Tony Hawkins' Javelin about a year before so was horrified to receive a call from Tony telling me there was water pouring from the back of the pump. Just a fortnight earlier Garry Corner had to do his pump again having found the seal had split so expected to see the same when I pulled Tony's apart but in this case the two halves of the seal rubber had completely separated which leads to the question as to why.
New seals were sent down overnight from our Jowett Parts (excellent service as usual) so could study these which look very good and compare with an original one that Bryan Spragg had given me. If you sit them on the bench side by side the new ones being supplied now are about 2 to 3 mm taller than the original. Also the coil spring in the new seals is much stronger and a heavier gauge than before so they don't compress as easily.
Now as has been documented before (but sometimes forgotten -I had -) these new seals should not be compressed more than 2 to 2 % mm but unless some machining is done, when the waterpump is bolted together the seals are fully compressed and the spring coil bound as a result, so the new seals are very much overstressed leading to a very short life. So how do we solve this problem?
In the case of the front seal it is easy to see when the face of the impeller contacts the seal. Place a tube of some sort, the same length as the boss of the front pulley and by winding the nut on, take note how far the shaft comes through the front bearing race before stopping against the shoulder on the shaft. If it is more than 2 % mm then the difference has to be machined from the impeller, or the housing bored out by the same amount. I chose to machine the impeller (much easier) on Tony's pump by 2 % mm. This then gave the required nip or crush of 2 % mm of the seal. Because you cannot see the rear seal more care is required. Clean the front hOUSing where it enters the main pump body so that it fits together easily. Fit the rear seal and then push the front housing (the shaft must be tightened up to the shoulder) with the gasket in place of course and you should feel when the impeller touches the seal. Now measure the distance from the flange of the front housing to the face of the main housing where it bolts up to. Note this measurement and take 2 % mm from it. This is the amount that has to be machined from the back of the impe!ler. In Tony's case it needed another 2 Y, mm from the back of the impeller which meant that I had reduced the original distance from the front and rear face of the impeller by Smmfln other words, if I hadn't done this the seals would've been crushed by 5mm, twice that of what is recommended.
For the fina! assembly seat the seals in their housings with sealant and a smear of vaseline on the face of each seal, then bolt the pump together. When turning the pulley there should some resistance but not excessive.
I gave the pump back to Tony to fit while I crossed my fingers and waited for the phone call. It came in the affirmative which was a relief. It made the National Rally OK so now time will tell as to how successful we have been.

It is imperative that a spacer / modified washer if fitted when using a sealed bearing. The build dimensions are critical to ensure the pulley clamps tightly against the spacer and bearing inner race.

All my pumps now have a modified keyway which is a vast improvement over the woodruff key.

I also suspect the new shaft made during reconditioning was perhaps not hard enough to hold the keyway. Should the shaft be hardened ?

No need. Use a good quality Stainless Steel shaft. I would not use a woodruff cutter to form the keyway. Better to use a 3.5 mm ( or smaller ) End mill and form a 4mm wide slot 2 mm deep to accept a 4 mm square piece of key steel.. You then need to enlarge the slot in the pulley to take the 4 mm key. Do this in the lathe with the chuck locked and use a 4mm wide chisel tool.
Completed over 1 dozen now with no issues.

The unit was from Bill, so anybody who has one may want to check the points Drummond and I have raised.

One issue with any mod like Drummond's is that you have to make sure the mods are well documented as later in life someone may try to reassemble with the wrong parts. It is bad enough keeping track of all the mods Jowetts themselves made on the pumps over the years. Knowing what fits with what is quite a challenge. In this case the pump was put on in a hurry to get the car ready for its debut and we did not have the luxury of time to check everything even if we had the knowledge which many would not.

I think this keyway mod is excellent as I regularly have trouble getting that semicircular key to sit down. Some less diligent people have probably tightened up the nut with the key squashed in the wrong position.

The SC also had a broken thermostat which is not something I have experienced before. Whether this was caused by the boiling water and water pump failure we will never know. The SC resolutely refuses to get hot normally. After installing this new stat a road test and the temperature measuring gun proved the stat remained closed even after a fairly spirited run on a warm day. The heads remain at about 70C with the header tank and rad sitting at 41C. Perhaps more investigation is needed....closing the heater valve off perhaps.
It had also found its way up the pipe so as well as the circlip I fitted a wire restrainer dispensing with the stainless steel washer.
Thermostats come in different temperatures, my collection has from 70 to 85 deg C. Ben Shaw use to prefer the higher value claiming it gave a more efficient engine. I chose the 77.

Note I checked it opened by putting in near boiling water.