Friday 11 April 2014

The Cooling System (2)

Time to look at the Cooling System.  See this post for a description of the problem.   With all the recent short journeys I found the engine just never warmed up and that is not good for her in the long term.

So first I fitted the thermostat.  No problem, only 2 bolts and it came with a new gasket.

Then I mounted the new variable thermostat switch onto the chassis. 

 Not ideal, as I can only adjust it with the bonnet off, but I could not mount it any further away from the radiator.

The instructions tell you to put the probe into the top hose, but I found that was much too tight a fit.  So my first experiment was to mount it on the radiator down tube.  

Singularly unsuccessful, the temperature did not register.

 So the next step was to mount it actually on the top tube.  The advantage of that is that I can play about with it without having to remove the nose cone.

Then came the problem of refilling the water.  The design of the Superspec cooling system is very unusual and non-standard.   There is no radiator cap on the radiator itself, but there is hose coming out from the top of the radiator with a tube leading across the top of the engine, and from there into the expansion bottle (see picture above).  Unlike most expansion bottles though, this one is pressurised with a radiator cap.   Half way along the top pipe is a bleed screw that needs to be undone to allow air to escape from the radiator while it is being filled.

So I refilled the system through the expansion bottle, until water came out of the top hose, being slightly surprised at how little it took before it was full (Hindsight is a wonderful thing).    Then took the car out for the first run, minus nose code and bonnet so I could see what was going on.  As I arrived at my front gate one of the neighbours walked past with his dog and stopped to chat.   After about 2 minutes I  noticed the engine was running quite hot and he then pointed out that water was pouring out underneath from the front of the engine.   I checked the 3 connections that I had undone to work on the system (Bottom hose to drain it, thermostat housing and top hose to try and install the probe) and all were watertight so I had no idea where the water was coming from (and I never did find out).   

So back into the garage to check it out.  Couldn't find anything obvious, but checked the water level and managed to get another pint of water in so decided that was the problem.   Took the car for a 3 mile drive and found it was up to temperature within about 400 yds and then gradually got hotter and hotter.  As it entered the red I switched the fan on, but the temperature remained just under the red line.   Once parked in the garage the car made a very peculiar whistling noise, eventually traced to the expansion bottle pretending to be a kettle and the water was boiling.

This is the point when you start thinking of the old saying "If it ain't broke don't fix it" and wishing you hadn't started.

However, as I have said before, the Robin Hood club forum is a fountain of knowledge so it was onto there to search for answers.  Two things were immediately apparent:

1.  Because of the unusual design it is very difficult to get rid of air locks in the system and that gives exactly the symptoms I was seeing.   An air lock prevents proper circulation so the engine rapidly heats up and then overheats, putting the fan on doesn't help because not much water is going through the radiator, and because their is air in the system, it doesn't pressurise properly and the water boils.

2.  Running with the bonnet and nose cone off makes the situation worse as the air is not being forced through the radiator to cool the water.

Luckily the solution is fairly straightforward.  In fact the system will eventually self-heal, as once the water is circulating the air gradually gets pushed to the top.   So I topped her up once again, getting a least 2 litres in.   On the next drive the temperature was still too high and back in the garage the 'kettle' was still boiling.  But I was encouraged by the fact that it only did it for about a minute and also there was no sign of any water leaking out.   So yet again I added more water until the radiator was full.

Next day took her out for a 10 mile run with the nose cone and bonnet fitted and was really pleased that she took about 2 miles to come up to temperature and then sat on the low side of normal for the remaining 8 miles.   Back in the garage, no 'kettle' and no water leaks, so fingers crossed, it looks as though I have eliminated all the air locks and the system is now working perfectly.   Will probably try another final fill up when she has cooled down.

Now I need to figure out how to get her hot again so I can adjust the thermostat to switch the fan on.

Although it was slightly worrying, again I have learned more about the car.  I love the fact that she just doesn't behave like a normal car, and has much more personality    

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