Mark w

Ive booked a room at the Prince Llewelyn B and B . Its just a couple of miles from the circuit .They say they are doing breakfast - but it might be in your room . They have space outside for a trailer if your still looking for a bed . As far as food is concerned i am taking a chance that the local chippy will be open ( if nothing else ) .Its a while away yet and things are now opening up in Wales .

Have you thought about lighting a candle and lowering it in to see better ?

The other thing I've found out today is that the oversized pulley for the water pump will fit on my S3 despite all the plumbing in that area . I am not going to fit one just yet because I am not sure the 620 needs it but that may be included in phase 2 of any changes .

Ok so after James Bs nag I will post an update . New thermostat housing ordered ready for alteration Bypass hose ordered Doctor has sourced and ordered the modified rear water outlets with the correct tappings and outlet diameters . A couple of alternatives for the bottle feed connection have been trialed . Neils idea seems to be the most promising so a mock up has been made in true Blue Peter style . Neil any comments on this last bit ? It's a -8 fitting and the top entry elbow can be 90 degrees now we've moved the male fitting to face vertically .the internal diameter of this fitting is exactly the same as the internal diameter on the exit from the bottle . ps your not commenting on my woodwork skills just the principle !!

If you look at the Caterham aluminium housing you will see that the thermostat is only fixed in position on one edge . In the Plastic housing its fixed tight on both sides . If the flange of the thermostat is thin and flexes under pressure its conceivable that the stat in the aluminium housing bleeds round the edge on the opposite side to the single fixing point as well as through the machined cut out , even though the stat is notionally closed . Just a theory , ive not taken it out to look yet but if its a sloppy fit it wont help.

Given the recent change in direction of this thread i am going to stop posting here after this post . The 620R was developed as a track car , originally it had no thermostat and worked fine for its intended use .The design incorporates a massive amount of cooling to deal with constant track use , large radiator, big oil cooler , intercooler and supercharger cooler .As one of the first 7no 620R owners ( who used his "track car " on the road ) i approached CC and asked them to look at introducing an upgrade to include a thermostat .It took from 2014 to 2016 for them to do this but after having this fitted ( FOC by CC ) temperatures were better controlled , not perfect in colder weather ,but better than nothing .It was an adaption to the original design NOT a start from scratch design. I was happy to " muddle through " with a radiator blanking plate in the coldest weather, i had after all had to do that with my R400 K series previously. My car is 6.5 years old now and has done between 10 and 20,0000 miles. You dont do that sort of mileage without driving a fair bit on the road .Ive not had bore wash issues , its reasonable economical on the road - maybe 30-35 mpg and i know when it needs a bit of help keeping temperatures up. There isnt a need to remove and replace the radiator blanking panel every 1/2 mile , ive put it in driving to a circuit early in the morning and forgotten to remove it for the first few of sessions ! , the cars coped fine , it never overheats. Marks recent thread got me thinking about this again and with Neils help i better understood the Duratec standard cooling system design and the way the 620 has been plumbed . The basic issue is packaging , theres just not much room available for a third connection to the Duratec thermostat housing with all the supercharger plumbing in the way and the " cold bleed " design CC have adopted with the aluminium housing isnt optimal for cold weather road use . I think there is a design solution to this ( without going to the extreme of an ECU controlled variable speed electric waterpump ) and have ordered a few parts to trail fit , basically i am going to try and eliminate the cold bleed and introduce a proper bypass and feed the expansion supply into the thermostat housing as Ford intended . Who knows if i will be successful but i like the challenge .It might be better on the road but overheat on track!! Posts above about "cars costing £50K should be faultless " make me laugh . Ask the original owners of £125,000 991 GT3s if their cars were faultless ! The engines grenaded with regularity and Porsche had to stop making them for about a year whilst they tried to find out why .This was the same manufacturer that launched the 997.2 GT3 with centerlock wheels ( one nut to fix ) which kept falling off on track when the hubs cracked under load and collapsed .I had one of those ! These offerings were from the worlds most profitable car maker who has an almost unlimited R and D budget . Caterhams are an acquired taste , brilliant at some things, poor in others. Everyone has different priorities and those that can adapt their cars to suit their requirements , where they cant they move on . Igor and i will develop our thoughts and get the alterations manufactured and trialed. If you see me out in January with my temperature gauge showing a steady 90 you will know ive cracked it

Whats with all these Private Messages sent , i thought it was a club forum for the benefit of members ???

That's a shame . Neww water outlet is approx £125 , other parts about £25 .£200 for a new thermostat outlet if you don't modify the existing . I am just looking for someone who can aluminium weld and I should have a solution .

I am going to order some weld on fittings and mock up something in wood to see if it fits . it might have to be a weld on spout onto a block ala #162 as the bolt on fittings ( onto welded male ) need space to turn the nut which then increases the size of the block needed ..... maybe the smaller of these ? something in between these sizes might be better but I've not found one yet .

For example , these don't fit , the projection is too great

ive sent the dimension restraint info to a number of suppliers and as you cannot use a screwed elbow fitting you need to fit an adaptor into the housing and then fit an elbow to it , even the compact elbows are too big to fit in the space . That's why I started looking at banjo fittings ( on the suggestion of one of the suppliers )

Having found a manufacturer who can resolve the rear water outlet design requirements i am still hunting for a solution for the expansion bottle connection into the thermostat housing .Given the space constraints and the position of the existing welding what do the engineers amongst us think about drilling and tapping the aluminium thermostat housing to take a Banjo connection for the expansion bottle connection ? Space constraints mean that a 16mm ID pipe connector is out of the question but this might fit . 3/8 NPT into the housing with an AN8 connector that would take a barbed hose connector .

Re item 1 i found that this went away when i had carefully set the throttle body to bleed the correct amount of air at idle. The throttle bodies come to CC pre set but in my case it was too far open causing the ECU to hunt around as it was trying to maintain the set idle speed . For anyone thats got Easymap the factory proceedure was:- Remove the throttle cable ( or slacken it right off ) , fully close the throttle by easing off the stop , set the TPS voltage to 0.40V ,open the throttle to 0.54V .This is supposed to give the correct flow of air at idle with your foot off the pedal , you might find you need a tad less air to avoid an idle speed thats high . When i looked at the map, load site 0 was 0.57V so having set the correct air flow i tweeked the TPS position to accord with the first load site so that the initial throttle pedal movement engaged the correct portion of the map. Keep us updated on point 2

I think the bypass is just badly drawn as the text covers the principle correctly . I know what you mean about the expansion bottle connection but provided the system is filled methodically , maybe with a temporary air bleed on the bypass circuit it should be ok given the alum housing seems to bleed a bit on its own . In any event it is a solution to returning more hot water to the block when the thermostat is partly open which may keep temperature up a bit . if anyone manages to successfully modify the thermostat housing please post .

Neil Ive just measured the gap and its about 25mm, ideally the pipe would point backwards but if it did that it would prevent the top bolt of the thermostat housing being put in place .The gap gets smaller as you move towards the back of the car as the intercooler pipework runs at an oblique angle .Its all very tight . Ive just come across this which adds a vent to the rad top but otherwise appears to follow my thinking , the header tank is plumbed into the radiator bottom hose .

Neil As i said above its not perfect but it does improve on the current situation . Show me a photo of a modified aluminium thermostat housing in situ with the standard intercooler pipework fitted and i will believe you .

This chap did it .

Mark, not necessarily a blind alley , possibly a pragmatic interim solution that's not perfect but better than the present arrangement . Getting an additional spigot onto the thermostat back plate without compromising the existing welding and allowing a pipe to be fitted in the confined space available is very difficult .

For anyone who wants to check their sensor is operating correctly Caerbont advise me it should give a reading of 250 ohms at 80 degrees .

Guys If you look at the Caterham parts site the temperature gauge for the 620 is now described as recalibrated . ive asked Caterham when this was revised and the guy that answered wasn't sure so I've put in an enquiry with Caerbont to get the detail . Will update everyone when I have the detail . Have also been working with " Doctor " on a mod to the cooling to reinstate the bypass . Getting there -slowly . NEIL Do you know the thread sizes for the two sensors that sit in the water outlet on a 620 ?

I watched my temp gauge avidly yesterday during the club track day at Brands Hatch . It was a REALLY hot day and the needle consistently sat at 75-78 degrees .Too low you say BUT i also noticed that the fan was coming on with the gauge showing a tad over 80 ( on the gauge ) . Even if the car had no thermostat i cannot see how it would consistently run as cold as 75 being thrashed in lower gears on a day when the ambient was up in the 30s .It just doesnt feel right . A couple of the K series were really suffering with the heat . I cant wait to get my PC back and plug in Easymap , keen to see what the fan actuation is set at and see if the gauge is showing the same temperature as Easymap is off the other sensor . PS i saw a post above suggesting readings as low as 40 . Is that right ? My gauge doesnt appear to register temp as low as this , its the bottom of the blue bar .....

I agree about pre sign on and briefing . This should be standard going forward , allows you to have a longer sleep and get up later ! it did seem to take an age to collect a wristband though .