Intake Manifold Thermostat - How do I check it and service it?

[Namerow]

I have one (1) 'Intake Manifold Thermostat' in my parts bin (PN 14100-E8850).  As you probably know, this valve is NLA from Nissan and appears to be NLA from all the Z specialty suppliers too.  Its job is to control the flow of coolant through the intake manifold heating cavities (which also duct out to the carb bodies for 1972-73 models).  I expect that it's arranged to work the opposite of the regular coolant thermostat:  i.e. it operates open when cold, then closes off flow once the coolant heats up).

According to the Parts Manual, they were fitted to the Z engines right up until July 1973.  I want to fit my parts bin unit to my '70 (which arrived with the manifold thermostat missing), but only if it's working properly.  I just tried a dunk test in boiling water and it wouldn't close, so I assume that it's jammed in the neutral/open position because of the usual chalky crud that can build up in a poorly-maintained cooling system (my unit hasn't been installed in an operating vehicle since 1980, so it hasn't been 'exercised' for a l-o-o-n-g time)

Does anyone have any experience with fixing these little thermostatic valves?  I can't find any mention of it in either the Z FSM or the L24 Engine FSM -- not even a note on a diagram to indicate that it even exists. 

Q1:  I'm thinking of soaking it in CLR, on the assumption that it's mineral deposits from tap water that are causing the problem.  Has anyone tried this?
 

Q2:  What's the correct temp. at which it should start to close?  And how long should it take for it to cycle from fully open to fully closed?
 

Q3:  Do I have the operating logic correct?  (i.e. normally open, then closed when hot).  Is it designed to fully close, or just partially close?
 

Q4:  There's a tiny phillips-head screw with an equally tiny lock nut on the tip of the internal centre shaft.  Has anyone tried to take one apart to assist in cleaning up the moving parts?
 

Q5:  Does anyone know of a source for these (either NOS or used)?

 

Any guidance welcomed.

[zKars]

I think you have the operating intention correct. Closes as the water warms. I have a couple of spares here, no idea if they work either. I'll dig up a couple and see if they work or respond to some CLR like you're trying.

[Zed Head]

A timely post, re the Panama problems.

I looked back to where I found a drawing of the thermostat placement and find also that Nissan has a check procedure.  Made a copy.  It's in the 1972 FSM, page EC-21.  I didn't find anything in 1973 though, and the Parts Manual shows it as disappearing in June of 1972.  Maybe that's Build date.

[Zup]

Page EC-12 and Fig. EC-20 from the 72 FSM indicate that the operation of the manifold heat control thermostat are as you all have described above. It closes above 150* F.

Fig. EC-20 shows a section of the thermostat. It may be that there is a mistake in the section labeling as there is the possibility that #7 Adjusting Nut and #8 Case Cover have been transposed in the image or vice versa. If so, there may be some adjustment to the thermostat as mentioned by Namerow.

(click on  TIF)

EC-20 manifold heat control thermostat.TIF

Edited January 10, 2016 by Zup
instuctions to open attachment

[Zed Head]

Cool.  I missed that one too.  Doesn't look like the "case cover" is threaded.  Looks crimped, so probably not unassemblable.

[Zup]

Zed-

Your post made me go look at the 72 FSM I have here in the garage.

I agree it  probably can't be taken apart, but thought it interesting that there is an adjustment nut as Namerow suggested.

Hopefully Jim K. will find his and free one up, or Namerow will get his working. That would be neat!

This photo is of the original rear manifold water pipe assembly from my 73.

 

I may be wrong, but I think the location of the manifold heater thermostat was moved to the rear manifold water pipe and the term for the device was changed to "Water Control  Valve". I'm pretty sure it is the silver hex sided piece in the photo above. (I know many will think that this is just a bunch of discarded plumbing pipe, but the only part that is NOT supposed to be there is the iron pipe cap at the end that the PO placed on it when he had this mess removed from the car in a conversion to  downdraft Weber carbs)

The "Water Control Valve" is  shown in the 73 FSM section EC-1 as #9.

Scan20002.TIF

 

[Namerow]

Very cool.  Thanks, guys. 

An update from my end:

• The labelling for Fig. EC-20 is, indeed, reversed re Items 7 & 8.
• The 'case cover' is simply threaded onto the main casing, so it's easy to get off (big hex-nut fitting).  After the cover is off, though, there's a brass cap (from which a central shaft with the adjusting nut protrudes) that looks like it's a press-fit into the main casing... so I'm probably never going to get to inspect the innards without destroying something.
• I've got my thermostat soaking in CLR now.  There was a lot of 'action' right off the bat, so my suspicion about mineral build-up might be correct.  We'll have to wait to see, though, whether it frees up the workings.
• Interesting that the designers decided to add an adjustment facility for such a simple device.  That may explain, too, why there's a threaded cover rather than just making the device completely sealed.  Maybe they knew something we don't !
• Don't know if anyone else spotted this, but the intended flow direction for the coolant is the reverse of what I would have expected.  According to the FSM diagram (unless this is another labeling error), when the T-valve is open, the coolant is flowing out of the rear bypass tube, through the T-valve, then into the manifolds, and finally exiting into the main thermostat casing at the front of the engine.  I always thought the flow direction was the opposite (i.e. from front to back, and then around the rear of the engine into the Y-fitting).  I guess I'll have to go back and look at those coolant flow diagrams that someone came up with in the midst of that long debate over whether or not it's safe to bypass the cabin heat coolant circuit.
• I'll report back tomorrow on whether or not the CLR soak worked.

 

[Captain Obvious]

7 hours ago, Zed Head said:

probably not unassemblable.

Wait... So it is assemblable? 

Edited January 10, 2016 by Captain Obvious

[Namerow]

Update - Sunday AM

Well, I'm afraid that the C-L-R 'de-liming' didn't work .  I soaked the T-stat main assembly for about 4 hours.  The bubbling action was strong and constant... so much so that it began to occur to me that the stuff might be dissolving something other than just mineral deposits (like brass, maybe). 

Anyway, I pulled the valve out of the C-L-R and repeated the 'blow test' (per the FSM-recommended procedure).  Used boiling water fresh from the kettle (showed as 195 degrees F, although immersing the valve probably dropped it to 180 - 185).  I sucked up the water into the valve -- to ensure that the pellet was actually seeing the hot water -- and then waited for over three minutes to see if the valve would close. 

No joy.

After this, I removed the hose that I'd connected to the valve and then clamped the valve housing in my bench vise so that the outlet port (i.e. hose end) was facing up.  With my inspection light, I could clearly see the tip of the tip of the pellet shaft, c/w the little E-clip on the end.  Using a small pin punch, I tried lightly tapping on the end of the shaft to see if it would show signs of movement.  Nothing.

Then I tried pushing down as hard as I could on the pin punch to see if I could move the shaft back against the internal spring.  Still nothing.

So I'm at an impasse here.  Non-functioning part that's locked in the undesirable position (i.e. always open, meaning that hot coolant will always be flowing through the intake manifold passages, even when the engine is up to temperature).  Don't know if it's seized, out of adjustment, dead, or all three.

As you can see from the third picture, the little lock nut and adjuster stem are tiny and both appear to be made of brass (i.e. fragile).  They also look like they're firmly attached to one another, so I'm reluctant to put a wrench on the nut to see if it will turn.  I'm even more reluctant to put a screwdriver in that itty-bitty slot to see if the 'adjuster' will turn.  Also, I'm not even sure how the adjustment works (I think that turning the screw may just move the whole pellet/shaft/valve downwards towards the valve seat).

I suppose that I could heat the assembly carefully with a butane micro-torch (that would certainly get the actuator pellet's attention!), although I'm worried that I might weaken or destroy the valve (presumably made of neoprene) in the process.

(sigh)

It's an interesting state of affairs.  Putting the valve on the engine in it's current state will be no better than just leaving it off -- and either of these approaches is non-desirable, because -- as note previously -- the result is hot coolant flowing through the intake manifold all the time.  If I simply block off the valve or its connector hose, it would seem to be a recipe for crud building up inside this part of the coolant circuit (and maybe even trapped air that could get into the main circuit and cause problems somewhere else).

I wonder if there's another car of similar vintage that used an inline coolant control valve like this?  If so, there might be an alternative solution.  If I knew that there was another part out there that I could conveniently purchase, I'd pry my Nissan valve apart to see exactly where the problem is.

Suggestions, anyone?

[Namerow]

More...

OK, I think I've figured out how the adjuster works.  I now see that there are two springs inside the assembly.  The inner one (small diameter) serves the obvious function of resisting the valve shaft's motion relative to the pellet.  The outer spring (large diameter) sits just inside the bore of the housing and supports Item 6 ('Supporting Case').  The pellet and attached shaft with valve are mounted to Item 6 (hence the name, Supporting Case).  When the adjusting screw is turned, it moves Item 6 down towards the valve seat, thereby reducing the pellet and valve closer to the valve seat.

Looking down into the main housing through the 'outlet' port, I can now make out the actual valve.  It looks like it's sitting about  3/16" - 1/4" off the seat.  That seems like a long way, so maybe turning in the adjuster screw would help achieve full seating of the valve (I've got about 1/8" of adjuster thread length available).

Time to get out the micro-torch and my miniature socket wrench set!

p.s. re Zup's photos and notes, that '73 valve looks like it's identical to the '72 unit that I've got.  The PO just unscrewed the top cap and inserted a 90-degree pipe elbow between the two parts.  The thread used on the manifold thermostat's main housing and cap is not a pipe thread (instead, it looks like a fine thread of ~ 19mm dia), so who knows how that pipe fitting was attached (hard to believe that the PO invested in a 19mm tap-and-die set).  I bet there's a lot of pipe-sealing compound in there!

[zKars]

I thought I remembered this discussion from hybridz. Interesting reading at least.

http://forums.hybridz.org/topic/109345-su-carb-manifold-heat-control/?hl=%2Bthermostat+%2Bvalve+%2Bmanifold

i promise to look at my valves today. was a bit chilly out in the shop yesterday. -25C in the morning, only +13C in the shop. Dang new infrared heater is not up to the task at -25C! Brrrrr...

Edited January 10, 2016 by zKars

[Mark Maras]

I think I'd put it back in the CLR for a longer soak. I had to soak my fuel tank sending unit 24 hrs to remove the rust on it. I thought the CLR would probably destroy the the very small wires on it. But what the hell, it was unusable as it was. To my surprise, the unit looks fantastic after a 24 hr. soak. No damage to it at all.