Smithy77

JK, thanks for your reply. I may have posted previously about the overcooling issue separately You will have also read many other similar sounding K cooling issues on track, but I've not seen anything like this specific issue myself. I think the indicated water temp was about 95C whilst idling back in the paddock, not sure about oil. Also measured temps of the coolant rail and top of rad using a laser thermometer and both were reading in excess of 100C but <105/110C from memory. I've since done some extensive testing on the thermo switch using the laser thermometer and it behaves perfectly, so we can rule that out. Next time on track will be end of Feb earliest.

Hi all, will try and keep this short and sweet, as far as possible. I have an original Minister built R400 K-series engine which the previous owner dropped into my car a few years ago. He later got it DVA tuned to produce 230bhp@8000rpm. I bought the car in Feb 2016 and had the engine rebuilt by DVA in the summer. Before the rebuild, I noticed it overcooled quite badly with ambient temps <15C. This was with a totally standard cooling system: no heater; standard bypass; standard ali K-series rad, 82C stat with a large(ish) jiggle valve in (think it had a Ford stamped somewhere on it). Fitting a new QH 82C stat with 2mm bleed hole drilled made no difference. Fast forward a few months after picking up the rebuilt engine. I decided to make a few cooling circuit mods to address the overcooling. The radiator was also weeping so I replaced this with a Coolex radiator, I'm told built to the same spec as the standard Caterham K-series rad, and I have re-used the old 9" Spal fan. I also decided to go down the Rover PRRT route: fitted a brand new genuine item (82C with soft pressure spring, as recommended) in the bottom hose between rad and submarine pipe; fitted a 32mm T in the top hose with 32mm bypass pipe to the PRRT; fitted a gutted stat/polo ring in the OEM stat housing to replace the removed OEM stat; and finally blanked off the old 16mm bypass between top water rail and stat housing. The results of this work on the road were fantastic! Now I have rock solid temps of 75-80C (indicated) in all conditions and all ambient temps. Now here is the "issue". Went on my first Caterham trackday at Castle Combe in October. Bare in mind this was my first time on track (with my own car) and first time owning such a high powered K-series, so I have little experience to judge this on. I was finding that after a spirited 15-20min session on track, and after a cool-down lap cruising round in 6th gear, once I got into the paddock the rad fan would stay on at idle permanently. I fully expected it to stay on longer than normal as heat soaks out of the cylinder head, but I'm talking about it idling for 15-20mins without the fan switching off. In the end, I don't think the fan actually switch off before I switched the engine off. Does this sound like normal behavior? If not, could I be suffering from an inadequate rad fan or even poor rad flow at idle? It should be noted that whilst on track, temps seemed perfect with water and oil never going beyond 85C indicated. I did have a minor gremlin (possible red herring) with the new cooling set up at first (before the trackday) whereby at idle, it showed the signs of little or no coolant flow through the rad. This was evident by coolant temp at idle rising up to 95-100C without the fan kicking in, but if you raised the revs to as little at 1300rpm, temps quickly began to drop and the fan kicked in. I put this problem down to two things: 1) the idle speed of 900rpm was too low for use with a PRRT, and I have since raised it to about 1050rpm, and 2) I noticed I was finding an airlock at the top of the rad, despite always bleeding properly when filling. When this appears I bleed it out by blowing coolant through the expansion bottle before tightening the bleed screw. With these two issues sorted, the system behaves exactly as expected at idle, with the fan switching on at 92C and switching off after a minute or 2 when the temp is down to 86C. No increase in revs is required. I'm slightly concerned about the air lock issue, but not overly just yet because I have not kept the cooling system closed for a long enough period to monitor it properly yet. Replacing fiber washers to drain plugs, swapping a used PRRT for new, and generally little usage in between has meant the air could just be a result of residual air from filling the system finding it's way to the top of rad. I'll keep a close eye on it though as I'm aware this symptom can often be the result of a dreaded HGF. On the plus side, during the track day, coolant level remained very consistent and only rose by 10-15mm after a spirited session, which is normal. I know a few members have experienced coolant blowing out of the expansion cap (along with airlock in the rad) due to the onset of HGF. Anyway, sorry for the long post. Any thoughts or advice greatly appreciated.

What years is this applicable to? Would quite like to badge up my 2002 Superlight in a similar genuine fashion

I bought the bits to do this myself after Track and Road said I needed one in the collector for mapping purposes, which is true. However, in the end I decided to just leave it in primary 4 and had a lambda boss fitted in the collector with a blanking plug. They simply remove the plug for when it is being mapped so they can fit their sensor. Save yourself the bother

As above really. Just stepping into the world of trailering to trackdays and wondered if anyone had anything lying around to help soften the overall cost of the "upgrade". Thanks

Regarding your fuel hose, I had a new braided hose made up by a local hydraulic trade store using the existing end fittings. Cost me about £15

Can you confirm tread depths please?

No worries. Don't expect much of a discount from Caterham new prices though

Have you tried speaking to any of the Caterham racing teams? I know DPR have some sets that they may be willing to part with

Jonathan, no we didn't. Just used the meter. Can anyone tell me where the driveby meter(s) are at Combe?

Tested the car with a mates sound meter, known to be very accurate. Peak of 95db at 4500rpm and 97db at 5000rpm - looks like I might be OK (for static at least).

I'm in need of 1no 8x13 standard superlight wheel. Went to fit new ZZRs in preparation for a trackday on 10/10 only to find one of my rear wheels is buckled! Anyone have one spare they do not need? Thanks

I got the dB limits in a muddle in my original post. Now corrected

Paul, do you mean the little tail pipe attachments? Certainly a good option. Also, you didn't hear it at WOT! Quite frankly, it is ridiculously loud

Dave, it a standard VHPD 4-2-1 race system, without cat and 24x6" Powerspeed can, repacked by myself with acoustafil only recently. Air filter is within the bonnet but I have an open air duct/scoop on the side. Jonathan, good suggestion. Fortunately, I live round the corner from Superwhite who has a decent dB meter, so I'm going to test the static noise this weekend.

Newbie to trackdays - wondering if anybody happens to have an airbox and/or dB slayer (tail pipe attachment) I might be able to burrow for my first trackday at Castle Combe on 10/10? Driveby limit is 87db/static 100db and I have an R400 K on roller barrels with 230bhp and I'm concerned it will be too loud. I don't want my first trackday to end in disappointment, but if I go armed with an airbox/dB slayer, at least I should be able run for the whole day and I'll then know if it is something I'll have to address over winter. Thanks in advance for any assistance

Talk to me

Can I have further details on the exhaust expander kit please, spec/web link etc?

See you on the track!

Thanks for your assistance Jonathan. Unfortunately, I already had the diagrams in the assembly guide but the engine loom diagram only covers a MEMS ECU set-up. I was wondering if there is a diagram out there which combines the MBE ECU specifically. Does such a thing exist?

Does anyone know where I can get hold of an engine loom wiring diagram for the above?

Interesting Garybee, I stand corrected - you have a good point Darren! I've ordered a new PRRT so will see if that sorts it first. If not, perhaps the pump could indeed be worth checking.

Thanks, will see what effect raising the idle to 1000rpm has

Darren - it had a new metal impeller water pump fitted for the previous rebuild in early 2015, so maybe 3000 miles on it. The pumps can leak or have nackered bearings, but I think I'm right in saying that there isn't really much else to go wrong with them which would effect flow rate. Titanium7 - I can see a couple of subtle difference between our set-ups. I see you still retain the standard bypass from coolant rail to OEM stat housing - this, in theory, should increase overall "bypass" flow and reduce rad flow. You also appear to have an R500 triple pass rad fitted? I think I'm right in saying these rads are higher resistance than standard rads, so again, this would, in theory, reduce rad flow. So, even though these two differences would, in theory, worsen my problem of lack of rad flow, you report no such issues. This would suggest, therefore, that my bypass diameter is not the problem and would point more towards the PRRT being at fault. One other potential factor here, Titanium - what did you have your idle set at? Mine is about 900-950rpm I think. It could be as simple as a low idle speed causing the problem. I found that raising the revs by only 200rpm or so was enough to get the coolant flowing through the rad.... Ivaan - perfectly valid question, and as Mankee kindly pointed out, we did indeed fit a gutted stat in the OEM stat housing

Hi all, My new K series R400 engine (with DVA mods running 230bhp) used to suffer (badly) from overcooling when it had a standard cooling set-up (standard rad, standard bypass, no heater, 82c stat with jiggle valve). Cruising with ambient temps of 10-15c saw the coolant settle as low as 60c I have replaced the rad with a Coolex item built to standard spec as the old one was weeping. I also decided to try a PRRT acquired from Mankee ( ) which was tested and seemed to be functioning correctly, age is unknown. So current plumbing has the standard 16-20mm bypass deleted with a "standard Rover" 32mm bypass between top hose and PRRT. The PRRT is fitted in the bottom hose between rad and submarine. For further reading and an understanding of how it works see here This mod has completely eradicated any over cooling and temps remain rock solid at 80c under all driving conditions. However, it doesn't seem to work quite right when at idle. If I leave it to come up to temp, all the hoses warm up with the exception of the bottom hose, as you would expect. The problem is, the water temp then continues to rise beyond 92c (switching point of fan) and will settle at about 95c. At this point, the bottom hose (before the PRRT) and lower O/S part of the rad is still cool while the top of the rad is too hot too touch and the fan has not cut in, suggesting that there is little to no flow through the rad. If I then rev the engine slightly, temps almost instantly start to fall and the fan kicks in and cuts out again at about 86c, so the thermo switch appears OK. I am hoping that some of the more scientific members could offer their thoughts on what is happening. I get the fundamental principles of how the PRRT works (from reading the above link) but perhaps there is something which someone else can see to explain this behavior. The PRRT relies (somehow ) on pressure to operate correctly and comes in a small variety of temp and pressure spring ratings (see here). I believe mine is the 82c stat with soft spring PEL500110, but I haven't verified this myself. I'm not sure if the "pressure" is required to help open the rad circuit or help keep the bypass circuit open. I read somewhere that the soft spring must be used on our engines as the pressure at idle isn't enough to operate the PRRT correctly with the harder spring versions, but I am not sure on the theory myself. My first thoughts to resolve this are: 1. Try a brand new PRRT PEL500110 with current plumbing 2. Try reducing the bypass from 32mm to 25mm to help direct more coolant through the rad Hope someone can help. Thanks in advance!