Jensen heritage for the next generation

Cooling System

Dear Diary discusses the cooling system to the Jensen FF chassis number 119/191

From the Jensen FF Mk1 sales literature in regard to the cooling system: “High pressure ( 0.948 Kg/cm2) system with pellet type thermostat. Twin thermostatically controlled electric cooling fans.”

To help solve my overheating problem, I bought ( from Customville American auto parts) 859 High Road Goodmayes,
Ilford,Essex, 1G3 8TG. Tel. 020 8590 1449.( don’t forget they have a delivery charge of £10.00 ) a Wizo high flow 160 degrees thermostat and gasket -£13.74


 Photo above showing the Wizo high flow thermostat

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Photo 1: A later 440 water pump and gasket for cars with air con.-£47.08 ( this arrived as an aluminum pump part no.. 18-510/FP1471) from Customville. Photo 2 : comparison of old and new.


Because I had an overheating problem in the very hot weather this summer I added water wetter. It did seem to improve things but certainly wasn’t a solution even though it cost £15.00p. I am going to change over to forlife coolant which is a complete coolant replacing the water all together. Forlife contains no silicates and also acts like a water wetter to aid the transfer of heat to the coolant. Water wetter can be added together with forlife and I understand this increases the heat transfer effect. Somewhere I came across the following:

“Inspect the coolant for…green slime resulting from silicate drop out. Silicate dropout leads to erosion of water pump seals and surfaces. An over concentration of either antifreeze or additives can promote green slime which blocks coolant passages quickly reducing cooling system efficiency. Most antifreeze solutions are based on either ethylene glycol or propylene glycol. Cavitation erosion causes pitting of the engine block as a result of the constant action of coolant vapour bubbles that continually form on the surface and collapse with enough force to erode the metal. The pitting leads to pinholes and cracks in the cylinder walls. Components in antifreeze known as SCA’s are the main line of defense against this, inside the engine.SCAs act as a protective sacrificial film over the metal and also prevent electrolysis between iron and aluminum parts. SCAs become depleted and hence must be replenished thus the recommended requirement of periodic flush and refill of coolant.

There is also some risk that these silicates will drop out of solution to form solids. These solids can lodge in the thermostat and block it open. More precipitation will occur if the coolant solution is made up of tap water, not distilled water. Many water companies add a small amount of solids like lime to the water. These solids can precipitate the silicone out of normal antifreeze solution. Use distilled water to prevent this. The solids may end up blocking the cylinder head passages as well. Most automotive manufacturers recommend refilling the cooling system with soft water that contains no more than 40 ppm chloride, less than 100 ppm calcium/magnesium (hardness). THE POINT IS….DO NOT USE TAP WATER; use only DISTILLED WATER (distilled using the steam method not the filtered or other lesser quality methods that leave impurities). Also, it is well known that a solution of more than 50% antifreeze can form an unpumpable jelly in the lower radiator hose if someone mistakenly thinks a higher solution will make for additional deep freeze protection.

Some coolants are compatible with each other and others are not. A mixture is incompatible if reaction causes chemicals to fall out of solution or another chemical reaction occurs that can result in damage. Remember traditional silicate-based coolants have a shelf life of about 18 months, which is when silicate starts to polymerize into silicate gel. ( the moral appears to be to use silicate free antifreeze and distilled water or one of the forlife coolants that is also silicate free)

Cooling system cleaners… Acid-type and alkaline-type cleaners are available and selection of the right cleaner for the specific problem is important. Alkaline cleaners are best suited for removing gelled silicate, while the acid cleaners perform better on rust and scale. Solder bloom as well as oil and grease can be cleaned with either type. Chemical cleaners need to be thoroughly flushed with clean water twice before coolant is added back into the cooling system.

dscn1067 Photo of fan configuration. I am upgrading these to Bosch. I understand they are available through Bosch UK at Leicester on Tel 0116 2814488. However, I bought mine from Ellis Components of Stonebroom Industrial Estate, Stonebroom, Alfreton, Derbyshire, DE55 6LQ, England.on 01773 873151 price £72.36 +vat +delivery(£6) Total £92.07p.each for the motor and 6 blade fan as one unit. . Fan being 280mm diam. ( part no. “3 136 613 262” – fan and motor together.) .Delivery was 3 weeks. My thanks go to a chap named James Barns who originally dug up all this information on part no.’s etc.His research info. can be found in the “tech Submissions” section of the “K & D Enterprises” internet site. In more detail what he says is this:

“Like many interceptor owners my attention has moved to the cooling system fans on my car. When I purchased 2340/1843 it was fitted with FOUR Kenlow cooling fans, two pushing and two pulling air through the radiator. The setup kept the engine cool but drew so much current that the fuses melted or the fuse box overheated !
Asking other owners what was best, always received the same advice – “Fit two Bosch fans”.
OK so I tried to find a part number / supplier in the UK. I had no idea how long it would take ! Listed below is the results of my research for other owners that want to fit two Bosch fan motors:
The required Bosch fan motors are the 12 volt members of the DPG series. The DPG series has a mounting diameter of 75.8mm and they fit the standard Interceptor “spider”/fan mount.
The required fan needs to be 280mm diameter for the two motor fan shroud and has been made with 2/3/4/5 and 6 blades over the years. The 4 blade fan is very efficient (in air flow terms) but is very noisy ! The 6 blade fan seems to be the best compromise – its part number is “3 136 613 262”.
The 12v motors have been made with a current draw of between <40 Watts to 100 Watts (they look the same but are not!). Some of the motors are single speed and others are two speed (two windings).
A lot of the DPG range were made for an OEM customer and very little can now be found out about the motors power ratings etc., other motors have been discontinued.
The most powerful motor that is currently available is part number “0 130 107 098” and is a 100 Watt item. That is the good news – unfortunately the motor was not designed to fit on the “3 136 613 262” fan. The shaft diameter and shank length are the same but a hole has not been drilled in the shaft and a groove has not been cut at the end of the shank. The hole takes a role pin to stop the blade spinning on the shaft and the groove takes a clip that stops the fan from departing the shaft. A small amount of light engineering is required to mount the fan on the motor – I have just completed the operation and it’s not hard ! Contact me if you need more info.
OK – so if you don’t want the most powerful motor you just want a simple life – what’s the next best option that is available ? Part no “0 130 107 237” is a 93 Watt motor fitted with the “3 136 613 262” fan (that’s correct fan and motor – one part number).
I have tried to find out what difference the motor will make – it can only spin the fan faster ? No luck from Bosch.
Spies Udo it the best man to contact and to date he has drawn a blank for the 100 Watt combo. His e-mail is
Udo has a graph for “0 130 107 237” and it shows the pressure differential (suck) in Pa and Volumetric flow in Cubic Meters per second. It must be remembered that this is the same fan blade and the extra power of the 100 Watt motor can only bring the motor to operating speed faster and maybe sustain it at a higher RPM – as long as the blades don’t stall, the extra power will mean maximum flow from a DPG combo ………. ?
Where do I purchase the items and how much ?
The best prices (7-2-01) are direct from Bosch at Leicester UK (Attn Gary Read – UK Bosch Technical) 0116-281-4488 (Fax 0116-289-2878)
3 136 613 262 Fan £2.89 Inc. VAT (Next best price £5.64 Inc. VAT Richard Ellis 01773-873151)
0 130 107 098 100 Watt motor £53.06 Inc. VAT (next best price £81.78 Inc. VAT Richard Ellis 01773-873151)
0 130 107 237 93 Watt motor and fan, Direct No quote (Richard Ellis price £83.66 01773-873151)
The items have to come from Germany and took 2 1/2 weeks to arrive.
Gary Read is the best Bosch technical rep in the UK with Steve Meloy a close second. Steve’s number is 01895-838897.
Good luck and stay cool ! James Barns

I understood, that the Bosch fan motor might foul the crossmember on the lower fitting because it is longer than the Lucas fan motor? Not so it just fits on the FF also the repaired and jointed top hose. This has now been replaced by a proper hose bought from Cropredy Bridge Garage part no……………….price……………………( Note: According to the Jensen works spec. sheets one of the fan motors was replaced under warranty at 74 miles due to it being “inoperative” ( part no. CT. 3149) and the top hose ( crossflow hose) was replaced under warranty at 1098 miles due to a leak ( part No. 26418)


As part of the cooling upgrade it was suggested to me that I utilised a fibreglass fan cowling from the MK. 2 . I bought one from Rejen for £45 + vat. I replaced the rubber flaps with some thin ribbed rubber floor mat. Relatively easy as it was just riveted onto the cowling.


However, on removing the radiator I discovered that the Mk1 rad. was smaller than the cowling( see photo of removal and cowling positioned on top of radiator) I asked the list about this and received the following reply:

1. I was never very impressed with the way the fans on the Mk 1 just whirled about in mid air, neither did I like the look of them or the 4 metal blades ( they worked OK) so I too bought Bosch fans and thought I would fancy a Mk 2 type cowling having just bought a new one from Robey I tried the cowling out on the Mk 1 first and BINGO, it didn’t fit because the MK 1 radiator is a different shape and size. Determined that I would have a cowling on the Mk1 come what may I made my own cowling. And very nice it is to, concours standard and definitely makes the engine bay look much nicer. However because the radiator is smaller and also the cowling I was able to fit only one running vent/flap. Net result – the engine runs hotter when I get into light traffic but when the fans come on you have never seen an engine cool so quickly.Moral, think it through. I keep on meaning to remove the cowling and just go to “spectacles” which must be more efficient than my old fans just mounted on a bar, but when it comes down to it the cowling looks much nicer.

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used an angle grinder to slice off the bottom section so the cowling was now of the right size. I then bolted the removed bottom section back on some 2 inches further up and cut the bottom two rubber flaps down to size. Re-attaching the bottom section in its new location returned the cowlings rigidity and the two bottom mounting holes for the bottom securing brackets. I bought a rubber seal to go between the cowling and radiator from Woolies.

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Photos of radiator removal

In the end I opted to get the radiator recored. This was done by “Motorads” ( radiator and heat exchange and repair) Windsor Road, Redditch, Worcestershire B97 6DJ. Took 2 days and cost £148 +vat. .I was told that my radiator appeared to have been recored once. It had 158 tubes measuring 12mm x 2mm in 5 rows with 16mm spacing between each of the tubes. The new core would have 204 tubes measuring 14.6mm x 2.2mm in four rows with 10mm spacing between the rows. The old radiator also had 11 cooling fins per inch whereas the new one will have 15. I was advised that having 5 rows of tubes in the same width isn’t necessarily more efficient because as they sit behind each other and as the air flows through the radiator the back rows are faced with warmed air (from the front rows) and the temperature differential is therefor less. Properly designed four row rads having greater water volume will be better.


I had to cut the cowling round the inlet hose point on the radiator. The Bosch fan at the bottom just fits. The upper Bosch fan was actually bought from a local car restoration show for £25. It is a new 2 speed fan and is slightly longer than the other one. Whilst driving at reasonable to high speeds the temp guage sits just over midway between cold and normal, even in the summer months. In the summer months if I am doing spees of between 20 to 30 mph then the fans will cut in occasionally and this is probably due to cows restricting airflow. The fans, however, very quickly reduce the water temp in these conditions or when idling. Also as one of the fans is a two speed fan I have connected the low speed setting to a manual switch so that I can switch this on manually when idleing in hot weather before the temperature rises to far. This helps reduce the number of times the main fans (on full speed) cut in and out.

I have now also improved the wiring to the fans as the Bosch fans draw 10 amps each as opposed to the Lucas ones at 7 amps each. One of the best places for electric stuff is Auto sparks ( They will also send a free catalogue. I bought a few metres of 17 amp pvc cable (size 28 in catalogue) and wired each fan motor separetelly with its own fused relay.

I have received the following e-mail observations in regard to the cooling system:

1. Some time ago you wrote the e-mail below. I have been looking into the subject of radiators and thought you might like to know who made your cores. The 5 row was made by Covrad as a “special core” …… Contact Ray Cooper 024-7667-5544 The 4 row core is made by NRF, “S 100” pattern …. Contact Amanda ? 01327-300242. PS £148 + VAT is a good price!
2. If the fans pack up on you and the fuses are OK it is probably the thermo switch, located towards the bottom, on the left hand side of the radiator. To test it just pull the rubber covered connector off and join up the connectors. If the fans come on its the thermo switch.