Cooling System Updated (Again!)

1. As advised by Tiger I originally ran the car with no thermostat and no bypass plumbing.  I understand this is a fairly standard set up for race cars.  However, if quickly became apparent that the engine was being over cooled.
2. My next configuration had a thermostat with a 3mm hole in it as a bypass.  This worked very well all summer - the engine stayed at a constant 88oC, unless the fan needed to cut in.
3. Once the cold mornings of autumn arrived the engine started to run cool again.  Things were fine at lower speeds, but once there was a significant air flow through the radiator the coolant temperature struggled to maintain 80+ oC.  So I decided to introduce a full bypass pipe and fit a thermostat with no bypass hole.  To do this I had to fit a thermostat housing from an earlier Silvertop Zetec.  This was necessary in order to fit the coolant temperature sensor in a place where it would get a reading prior to the thermostat opening (as the Blacktop Zetec housing has no sensor holes and I'd previously had the coolant sensor in the main pipe to the radiator).  This set up generally worked very well, but there was one problem: somehow air from the expansion tank would make its way to the top of the radiator, which is higher than the pipe that feeds it from the thermostat housing.  A little bit of air would get trapped there each time the engine was run until there was sufficient air there for the flow of coolant to break down - not good.
4. So one more modification and hopefully the final configuration.  A 8mm hose barb was welded on to the top of the radiator and plumbed into the pipe joining the thermostat housing to the expansion tank. Now all works well.  Any air can return to the top of the system and an added bonus is that the hole coolant system is now self bleeding, which will help when I come to renew the coolant at future services.

Here is a schematic of my final cooling configuration:

8mm hose barb welded in to the top of the radiator.  It is just above parallel with the ground.  This is to allow it and the pipe to fit under the curvature of the nosecone.

Full routing of the new pipework (apologies for the poor quality mobile phone pictures, must use the proper camera next time).

C-shaped brackets were fabricated from aluminium strip.  These were fixed under the camshaft cover bolts and rubber lined p-clips were riveted to them.

Radiator Leak Repair

Since first getting the car on the road there has been a very slight leak from the radiator bleed bolt.  I'd tried tightening it up a number of times, including using PTFE tape on the threads, but it always continued to leak.

I tried one more time, but unfortunately this time I overtightened the bolt and stripped the thread in the radiator - turns out the tread is just tapped into the aluminium so is very weak. My solution was to re-tap the  hole to a larger size (M10 x 1.5mm thread) and use a spare cap head bolt of the same thread that I just happened to have spare.

Once the bleed bolt was fixed I could get back to investigating the leak.  Upon closer inspection it was not the bolt that was leaking at, but a pin hole in the weld around it!  With the engine running drops of coolant would slowly form.  I decided to leave this for a while as the coolant was only coming out very slowly.

Many miles later I got a coolant overheat warning from the Webcon ECU.  Turns out there was air in the top of the radiator and the coolant was no longer flowing properly.  The cause was air being sucked back in through this tiny pin hole each time the engine cooled down.  Something had to be done to fix this. I took the front of the car apart and removed the radiator.  This was when I discovered that the pin hole had turned into a crack, probably about 10mm long.  The body of the radiator was starting to split.

I quickly took the radiator to the friendly local welders who re-made the weld over the area where the crack was.

I'm happy to report that after a few hundred miles of use there is no longer a leak in the radiator.  This gives me added confidence for longer runs, particularly with another trip to northern France booked for later in the year.

Minor Thermostat Leak Fixed

When fitting the 1.8 diesel thermostat I installed it with the rubber gasket that came with it.  Unfortunately this is slighly thinner than the Zetec petrol thetmostat gasket, and as such I had a small coolant leak from the thermostat housing.

I've taken it all apart again and fitted the original petrol thermostat gasket to the diesel thermostat.  Just been for a test run and no more leak.  Coolant temperature still fixed steady at 88 degrees.  Finally happy.