620R cooling

[Mark w]

 Water outlet , no bypass pipework .

[Mark w]

Apologies , top photo is upside down ! 

[7 wonders of the world]

Hi Mark,

The hose to the pressed in metal pipe above the stat housing is the bypass hose and is designed to circulate water from the rear of the head and discharge directly onto the wax bulb of the stat, which aid warm up as there is a circuit around which coolant can flow and makes for rapid, timely and accurate activation of the stat.

Your system has a tiny tiny bypass as this hose is fed via the bleed hose to the expansion bottle and therefore does none of the above to any great effect.

Do you have a photo of the stat they use..? as if they are merely taking the guts from the OE ford one this will create another problem as it is designed to close the bypass as the stat opens - if it does this in your set up it we block the bleed circuit from the bottle (this bleed circuit would normally feed back in via the heater return via the 16mm hose which is in the OE plastic stat housing and has been omitted form your ally housing).

 

[ChrisC]

Isn't there also a bypass effect with the drilling / shape of the thermostat housing, although not so much bypass, more like "stat close, low flow through the rad, and bypass via the expansion tank", "stat open, high flow through the rad" 

[Mark w]

Hi , Sorry no stat photo .My guess is its a traditional unit that just sits in the machined recess in the deeper alloy flange on the replacement pipe inlet pipe  .

The flange has a recess milled into the back at the top that coincides with the position  of the " bypass connection " on the block , possibly overcoming the potential problem to which you refer ? 

I do agree that its possibly odd that there is no bypass pipe from the rear of the block to the stat but its worked fine since 2014 .

The only issue is the one that Mark alluded to in the first post and thats one of overcooling in low ambient temperatures .Most Caterhams dont get used much in the winter ,if i use mine i just blank the rad a bit and its sorted . Other wise it works fine , holds a fairly constant temperature and never overheats .

[CtrMint]

I've asked Oakmere to check with CC, see if they can confirm if my 620R has a thermostat.  I'm still none the wiser.  Oakmere said they thought all 620 models had thermostats, the concept of no thermostat was a new one to them too. 

 

[7 wonders of the world]

#30

This is the OS stat 

https://caterhamparts.co.uk/other/4378-thermostat-82-deg-c-r300-race.html?search_query=thermostat&results=11

Still wondering if CC take the metal parts out and insert them into the alloy housing - 

The milled section you show in your photo is in the same area as the OE heater return line which returns water post heater matrix to the engine side of the stat, however in your photo is looks like this is incorporated to act as a constant flow of return coolant from the radiator.

This coupled with the lack of an effective bypass equates to what your seeing, over cooled and then temperature spikes as the stat cannot respond in the correct timely manner as there's no bypass to effect this, instead its relying on a much slower heat source from the tiny bleed via expansion bottle.

All in all a poor set up.

The stock Ford / Cosworth worked perfectly well in high output application, I'm just 38 BHP shy of 620 with no problems at all running the 82 degree stat linked above and the OE bypass from rear of the head tothe pressed metal tube in the block, with my expansion bottle returning via the 16mm plastic feed on the stat housing above (no heater).

I also believe (but have not had change to confirm this) that the 630 runs stock crank and water pump pulleys.... can anyone confirm this..? as when you increase the engine speed beyond the road going redline of circa 7300 you overspeed the pump leading to cavitation which effects the efficiency of the coolant and means more work for the bleed into the expansion bottle.

Cosworth made oversize pump pulleys to slow this down allowing safe high rpm useage.

The other option is to use an undersize crank pulley but understandably CC wanted to keep the OE pulley as this affords more belt contact necessary for driving the Rotrex, and retains the torsional damper too .

 

 

[Titanium7]

Can I resurrect this thread as I'm having the same issue as the original poster. My car when driven, even in the summer constantly sits at 40C and only rises when stationary for example at traffic lights. Can this be right as I'm sure the car is over fueling at this temperature. Did anyone get any satisfactory solution from Caterham?

Below is my attempt of a schematic of the system in my car. 

 

[Mark w]

Have you checked that your temperature gauge is actually reading correctly ?

[Titanium7]

It appears to be ok as it does rise to around 80C and the fan kicks in when stationary

[Titanium7]

Also, with the positioning of the number plate by CC it virtually blocks any air to the oil cooler. Without a gauge it's difficult to know what temperature the oil is. There may be because of this a large difference between to two fluids.

[7 wonders of the world]

Ti 7,

Is yours a 620 too...?

[Titanium7]

Yes it is, on the front of this months magazine. 

[Mark w]

Re post #33 the red arrow on the left feeding the heater appears to flow in the opposite direction to the non heater variant . 
 

On the latter this pipe feeds hot water back from the engine via the engine exit , vent and expansion tank , this recirculating hot water from the engine to the thermostat housing . I cannot see how that happens with this heater plumbing set up .

 

PS 

Swap p the colours on the plan ( cold should be blue ! )
 

 

[Mark w]

On second thoughts maybe the flow on the diagram is just wrong . ( as well as the colours !) 

[7 wonders of the world]

cant see the diagram on #33...?

[Jonathan Kay]

Private Message sent.

[Titanium7]

Will amend the diagram, it was rather rushed.

[Mark w]

Here's the Cosworth drawing for suggested Duratec cooling . The 620 appears to follow this bar the extra circuit cooling an oil cooler on this diagram .

[7 wonders of the world]

Which is why your all experiencing the problems you are.....

The Cosworth version runs a Modine coolant/ oil heat exchange which improves the cooling circuit over yours as there is an increase in flow to the thermostat so this will improve response times - though still no where near as effectively as using the bypass circuit, since the flow is considerably less and the water is fed to the rear of the stat and not onto the wax element.

Expecting your cooling systems to warm up quickly, maintain a constant correct baseline temp, and respond in a rapid manner to sudden thermal changes when the ponies are unleashed is madness considering the only communication to the stat is via the bleed pipe, which is by design restricted to a 3-4mm bore !

 

 

[Mark w]

7 Wonders 

Is there a " standard " " back plate " that one could fit on the rear of the block and take a larger diameter bypass connection from ? 

If so it would be an easy T in to the current pipe that runs from the expansion bottle .

[Doctor]

Right mister, a lot of stuff you write makes sense. What is the cure?

[Mark w]

Possibly too small but what about removing the temp sensor on the left and using that tapping ? 

 

[7 wonders of the world]

Here you go.... there's a stock Ford hose (CC carry this in stock circa £16) which goes from the pressed in elbow to the other pressed in elbow in the block by the stat housing.

https://www.burtonpower.com/cosworth-water-outlet-cylinder-head-with-bypass-fitting-yd8100.html

Although listed as no longer available I bet a bit of googling will throw one up otherwise you could modify the stock Cosworth version.

Havent seen the exact outlet on the 620 but this offer location for temp senders etc too but I'm guessing its this one...?

https://www.ebay.co.uk/itm/DURATEC-HEAD-REAR-WATER-OUTLET-CATERHAM-COSWORTH-CSR-MOUNTUNE-RACE-RALLY-/183872054023

 

 

 

[7 wonders of the world]

Arh ! thats the photo I was looking for !