Saturday, 17 November 2012


I know I've mentioned this a few times in the past but just to re-cap:
A few years back, my 140 suffered from overheating on hot days and nasty heat soak issues. I more or less sorted this with an aluminium radiator, larger fan and additional electric fan, but also looked around for some alternative solutions.
An email conversation with an Australian enthusiast revealed that a common solution in the very hottest parts of that continent is to fit an electric water pump and to this end a company called Davies Craig manufacture just such a range of devices.

Davies Craig EWP115 Water Pump from Australia

A little research highlights a few other benefits:
A conventional pump is most of the time creating much more flow than needed but more importantly, sometimes not enough. With proper control, an electric pump's speed / rate of flow is determined entirely by engine temperature with the flow continually adjusted to maintain a 'set temperature point' regardless of external temperature and load.  This also negates the requirement for a thermostat and by-pass hose, thereby simplifying the cooling system.  The Davies Craig control system actually goes a little further. 
Temperature sensor will live where the Otter switch once resided.
A manual choke switch will take over from the hit and miss Otter.
On start up, to minimise engine warm up time, the pump just pulses, to avoid hot spots forming around the cylinder areas, then gradually ramps up to normal operation and maintains the 'set point'.  This can be programmed in anywhere from 75 to 95 degrees for either max performance or max economy.
Switch off and the pump will continue running just long enough to resolve the XK engine's heat soak issues.  The Control unit also operates an electric fan to work in conjunction with the pump.
Given that the Alternator is mostly generating unused power, and some of this is now running the pump, its a bit of a free ride, and with no belt driven mechanical pump, will give a small but real increase in engine power. 

Apparantly, the normal approach to installation is to simply remove the impeller or vanes from the existing water pump.  This means there are no belt or pulley issues to worry about, but the angle of the water inlet, at least on my car, pointing downwards makes the pump and pipe arrangement very awkward.  Additionally, it would be good to create some space behind the radiator to accommodate an electric fan.  I am also not happy about wrecking my original pump if the whole scheme ends in tears, which is entirely possible.  It shouldn't be too hard to make up a blanking plate with a water inlet pointing the right way so this is my starting point.

First try.  Shame it's destined for the scrap bin.
The inlet comes from the old radiator top hose fitting, cut down and welded to an 8mm alluminium plate, cut and filed to shape.  The plan is to simply drive the dynamo (now an alternator) directly from the crank (bottom) pulley.  Only when I try to establish the new V Belt size does it dawn on me that the dynamo adjustment now forms a perfect arc around the bottom pulley, so without the water pump pulley, the V belt cannot be tensioned.  Clearly whats required is a blanking plate which can incorporate an 'idler' pulley in place of the water pump pulley.  I roughly draw up what I think is required and contact proper engineer friend Christian for advice.

Now with added idler pulley - My drawing as a starting point
CAD / CNC drawings and machining.

In spite of his occupational workload, young family and ongoing E-Type restoration, Christian still finds time to convert my drawing into a CAD format and arranges to have the parts produced  using CNC water jet cutting and milling.

Converted into a proper CAD drawing

And then into actual parts - Everyday stuff for these guys but still
amazing to me.
Christian very wisely gives me the component pieces to play with before they are all welded together and it soon becomes obvious that the idler pulley idea is a complication we could do without.  Also the different water pumps and pulleys used throughout the XK engines life would mean that this aspect of the design would need customising for each iteration.  Another friend, Neil suggests using a pulley on the back of the belt (Cam belt style) as an alternative and the following day drops by with his collection of used cam belt tensioners (What else do you collect Neil?)

Cam belt tensioners - Good idea Neil, and nicely followed
through with a selection to choose from.

The simplest from the selection turns out to be a perfect solution.  Amazingly it fits exactly onto the block which was originally intended to hold the idler pulley bearing housing and I just need to have a special stepped bolt made to accommodate it.  I do have one small problem, I have no idea which modern car it is used on so if you recognise it please let me know. 

This is just so simple it's almost elegant - and it works a treat.
Much easier than adjusting the dynamo.

Just needs plumbing in.

The rest of the job is basic plumbing but needs to look good.  I think the pump will be located  just behind the RH front engine mount where most conveniently the block has a couple of bolts attached which appear to serve no purpose.  I can attach to these, some form of 'tray' with rubber base which the pump will simply sit on.  The inlet pipe to the blanking plate needs a heater inlet fabricating onto it and I am now wondering if  a booster pump should also be used to ensure the heater matrix is provided with a plentiful supply of hot water.  Anyway, that can all be sorted out in due course and I really need the engine back in before I start to seriously look at the plumbing part of the project.  I would expect that to happen around next spring.

Classic Car show at the NEC tomorrow - (Sunday 18th Nov)  Travelling down by bus, arranged by TYMC (local car club) Round trip of 360 miles - cost £18.00 !!!  Delivered to the NEC front door, no parking hassles or charges and I can read, talk or sleep all the way there and back.

Next Post beginning of December.