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Rebuilding the tii Warm Up Regulator (WUR)


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Hey All,

My orange daily-driver fouled it's plugs and started misfiring...simple fix to clean the plugs, but the deeper issue was that the WUR had stopped working, stuck in the down/cool position...that richens the mixture and bleeds air into the plenum.


I opened the WUR up, this is what I found:


The parts on the right are the spring loaded air cone/valve that has the top hat washer at the top. In the middle is the plunger of the thermostatic element.

Here's a view inside the housing, where you can see the hole for the plunger and the top of the wax thermostat up against some seal ring (there's normally water the other side and air this side):


Can't work out what is holding the black seal ring in that photo above...it seems solidly placed there.


Seems to me the thermostat is a traditional type,something like this:


Just that the plunger is longer in this case:


Here's a basic illustration from the Mahle website:


Mine doesn't move....tried freezing to minus 10C and heating to 100C....nothing. Only option could be to replace this thermostatic element with one that would accept our long plunger.......


But, how to get that element out of the body? I can't see how the element is sealed to prevent water ingress into the air chamber....maybe that black ring in the photo above screws-in from the other end of the WUR body?? Maybe I need to remove this end-cap?IMG_20210902_200016_copy_1316x734.jpg

That end-cap seems to be an interference fit or maybe the tube end is peened-over??


I searched but couldn't find any threads relating to rebuilding these WURs.... Do any of you have any info or experience in getting inside this thing or repairing it?? 

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Wes Ingram's shop reconditions WURs.  AFAIK, the thermostat is NLA, so a rebuild is usually just dismantling, cleaning and here's the most significant part...replacing the rubber seal between the upper air chamber and the lower water chamber.


I've seen that seal removed and it's just a think rubber washer.  Hard to see in your picture, but I've seen the mangled, deteriorated remains on the work bench.  The replacement being a handmade version cut from a sheet of neoprene.  Once the old seal is removed the thermostat falls out.


That's all I've got.  Hope it helps.  Nice pics and illustration BTW.

Edited by PaulTWinterton
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Thanks @PaulTWinterton for the hint, it was indeed petrified rubber. 


Once I dug that out I could withdraw the thermostatic element:


So, that confirms that everything comes out from the top and there's no need to disturb that metal cover at the bottom.


The water seal is just a single rubber washer that's compressed by a flat metal washer, in turn compressed by the spacer sleeve and the annulus screw at the top.


Now I need to source something that can replace this, thanks @lilmo for that link, seems there's a number of bespoke wax actuator manufacturers in China.



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I pulled the (working) unit off my black car to understand the wax actuator, as above the original is marked "20 110" that could mean that movement starts at 20 and stops at 110 (Unlike our cars water themostat which has a sharp opening starting at, say, 75C and fully open by 85C).


With the WUR in a pan of water, a thermocouple inside next to the actuator barrel, i got this (temperature against mm extension):



So, yes, its seems it's spec'ed to have 10mm stroke in the range 20-110 C



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Interesting scenario: 


When setting the cold start enrichment, the manual says to elevate the WUR rod and hold it in the elevated position with the special tool.  Having a tii in a northern climate I've seen the WUR piston/rod recessed 2-3mm when the car sits in near freezing conditions.  Hence the need to elevate and hold with the "Retaining Plate" special tool to set the fuel enrichment gap to 2.6mm at a benchmark position.  When the special tool is removed the 2.6mm gap increases (in cold weather).


See the following experiments at 35°F, 60°F and 175°F

WUR3_Specs xsml.jpg


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