Modified Thermostat for a 4.2 Series 1 E type

[44DHR]

I have now received my modified 74 degree opening thermostats from WatJag to suit a 4.2 Series 1 E type with the side by-pass slot in the inlet manifold. This new post follows the earlier post "Thermostat", which was becoming confusing with the earlier 3.8 Series 1 having a different thermostat housing and the later 4.2 Series 2 inlet manifold using a different method and thermostat with a plunger mechanism to block the by-pass hole directly below the thermostat.

My 4.2 Inlet manifold has a by-pass slot using the thermostat cover, Jaguar part number C23233. This particular manifold is a "Warneford" for triple 45 DCOE Webers, but the stock Jaguar manifold has the same by-pass slot arrangement.





The manifold internal diameter is 50mm and the modified thermostat has a moving sleeve of 48 mm diameter which when up to temperature, the sleeve moves inward to cover the by pass slot. The modification made to the thermostat is to reduce the mounting face depth and also reduce the sleeve depth. The main body and sleeve are made of brass.







I hope this helps with this issue, but Colin at WatJag told me the setting up and machining costs mean that these will be around £25 each to supply. The good news is on these 4.2 Series 1 manifolds, the C23233 thermostat outlet remains untouched and the WatJag modified thermostat is a straight replacement fitment.

regards,

Dave

[David Oslo]

Dave

Good idea starting a clean thread, the first one had so much info it got confusing, especially when I read up the www.bobine.nl and the georgiajag articles.

You cut-down thermostat from WatJag looks interesting, I guess it replicates the function of the C3731/1* from SNG, in that it has a short sleeve downstream of the bypass slot, and when at right temp the sleeve moves upstream and blocks the bypass. Just what I need !

Do you have any idea which "donor" thermostat WatJag start off with? My thinking being that a careful slicing with a thin blade on the trusty angle grinder may be cheaper that ?25 to either WatJag or SNG.

Just noticed that both the sleeve and the mounting disc have been trimmed (look for the cut edges). Could this be the Land Rover 532453 thermostat that has been modified? If so, cheap as chips :D

[44DHR]

David,

I just cannot believe the amount of correspondence regarding these thermostats ! I can confirm your thinking in the case of Series 1 4.2 thermostats, such as mine pictured.

My money is on Heuer's posts which have been consistent and plain good sense - especially his 5th April 2016 comments in the latest "Thermostat" post. Heuer previously reported in the original post on the water pump mis-alignment - which spawned all these debates on thermostats - that he had "Just received the Wat-Jag thermostat and machined housing to try. The Western Thompson thermostat is from a SII/SIII Land Rover (part number 532453) and is larger than the SNGB C3731/1*."

Bearing in mind he was referring to a 3.8 engine as his outer housing had to be machined, but I take it that the thermostat is the same item. The word "larger" refers to the diameter of the moving sleeve, which by being larger, more effectively covers the by-pass slot in the 49.5/50 mm bore of the inlet manifold. This to me is the main benefit of the WatJag modified thermostat over the SNGB C3731/1*, in that the WatJag is 48 mm in diameter as opposed to the 47 mm of the SNGB unit. Also the WatJag is a 74 degree unit, but I thought the SNGB unit was originally a higher temperature unit, but now just checking SNGB website, they do show it as a 70 to 75 degree unit. At least all this lengthy debate has assisted us E Type owners to now have a choice and well done to SNGB to quickly sorting their website to reflect this as an E type item. Their C3731/1* is currently ?25.01, so priced similarly to the WatJag unit, so take your choice.

I did ask Colin at WatJag what was the basis of the thermostat and he did not give me a clear answer, but I can confirm it has Western Thompson stamped on it, so again my money's on Heuer's advice above.

regards,

Dave

[Heuer]

I have a Wat-Jag 4.2 modified thermostat on the way to me so I will report back when it arrives. Colin sent me these photos in the meantime:

[Heuer]

Just received the Wat-Jag modified thermostat which is a cut down LR 532453. Sleeve diameter is 47.6mm, about 1mm less than the unmodified version. I think this is due to the fact the original skirt flares at the end but the modification takes that off. So not much to choose between the SNGB and the Wat-Jag versions.

[David Oslo]

I've ordered a couple of LR 532453 thermostats which will duly arrive at end of month at next Ryanair family visit. One to modify and one as a spare if the angle grinder slips :D

I am particularly interested in the diameter of the sliding sleeve element on the LR unit, in terms of better blocking of the bypass port.

I will report back, but it'll be in 3 weeks time, and at the rate this debate thread is going someone else will have already done it and reported !

[Heuer]

Well just fitted the Wat-Jag thermostat and I have to say I am disappointed. The original moving skirt had a flared end and by reducing its length this has been lost. This means the skirt diameter is now 47.2mm whereas the manifold bore is 50.7mm, so whilst the skirt will cover the slot at operating temperature it is not going to be a very good fit with a gap of about 1.5mm all round through which water will bleed. Of course the design of the 4.2 cooling system is different from the 3.8's in that by-pass water flows not directly back to the pump but rather to the r/h side of the radiator and then back to the pump. The cross flow design of the radiator means the by-pass water is not actively cooled but passes down the side tank to the return hose; there will be some element of cooling though.

Width of modified skirt:


Width of manifold bore compared to modified thermostat:


The lip on the unmodified thermostat:


I will do some temperature measurements later but it seems to me that whilst the 3.8 skirted thermostat is worth installing the one modified for the 4.2 may not be as effective.

[Heuer]

Just been for a run and the temperature in the by-pass is the same as the temperature in the top hose so the Wat-Jag thermostat is doing nothing to block the by-pass. Not worth spending ?30 I'm afraid although the idea was a worthy one. I can't think of any way the diameter of the skirt can be increased.

[mgcjag]

Hi David a thin strip of brass could be soldered on the outside bottom edge

[Heuer]

Yes, that might work with a 1mm piece of brass wire or plate. However it is not a ready to fit solution.

[mgcjag]

Hi David..re the soldered on ring.....if the ones Wat jag are modifying dont work will the be prepared to modify further go include the ring...all the best..... Steve

[Heuer]

Would push the price up further unfortunately - I will speak to Colin at Wat-Jag.

[PeterCrespin]

Hmmm, some methodological inexactitude and technical misapprehension creeeping in here methinks...

How/where did you measure the comparative temps and what were the readings?

The temps being same, give or take, in a steady-state engine doesn't surprise me. Do remember the thermostat is a warming-up/blending device and is never an simple 'on-off switch' at running temps. Meanwhile, all the fluid compartments are somewhat contiguous. Marek went through this at some length elsewhere IIRC.

Pete

[Heuer]

Simple road test and feeling the temps with my hand. On the 3.8 the by-pass was cool after a similar run but that has a much closer fitting skirt. Rain stopped play and I did not get any further but I will do some more tests with an IR thermometer and the car as hot as possible.

[neal herridge]

David I know its more work but it was to keep that lip that I went the route of boring the housing & having a clamp ring as detailed in an earlier post.
It means you don't cut off the lip.
I need to get some more miles on the car to get a better picture but as you say there is not an easy fit answer.
Neal.