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Mr Polson

Stuck/Sticking Thermostat?

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Hey guys, while the LandCruiser is in getting paint I've been using a mix of both the ute and wagon to get around, and noticed a concerning thing about the wagon.
 
If I drive to work via the highway (two streets and then straight onto the highway), the temp gauge will climb to one or two bars above half before dropping back down to one bar under, then going back to half.
 
If I go via back roads where the speed limit doesn't exceed 50km/h, it never goes above half.
 
This morning though the gauge went three bars above half, and before I got the chance to pull over it was at hot, before dropping rapidly to two bars above cold, then going back to half.
 
Now to get more confusing it only does this on the first drive of the day. Doesn't do it on the way home from work.
 
I'm thinking the thermostat is stuck/sticking, or is there something else I should be investigating?
250 xflow, injected, unmodified, rad is 3 years old (was brand new), original water pump but was in remarkably good condition when I took it off, hoses are good (bottom one has spring in it), radiator cap was replaced with the radiator.

Didn't have a single issue on the recent 4000km mainland trip in 30°+ heat.

Plan on replacing the thermostat tomorrow evening.


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Maybe the thermostat is sticking? Does it have a small bypass hole drilled in it? If it does, is it free (not blocked)? The bypass allows a small amount of coolant to flow through to enable the thermostat to sense when it's warm enough. Without this bypass, there might be a stagnant, cool pocket just under the thermostat and it will stay shut while the coolant just circulates in the engine getting hotter.

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My theory ... try another cluster if possible.
i don't trust them. 

 

could be an air lock though/cavitation.. try bleeding it 

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Maybe the thermostat is sticking? Does it have a small bypass hole drilled in it? If it does, is it free (not blocked)? The bypass allows a small amount of coolant to flow through to enable the thermostat to sense when it's warm enough. Without this bypass, there might be a stagnant, cool pocket just under the thermostat and it will stay shut while the coolant just circulates in the engine getting hotter.

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From memory it has a bypass hole in it. I'd assume it's not blocked but guess I'll find out tonight when I take the housing off

My theory ... try another cluster if possible.
i don't trust them. 
 
could be an air lock though/cavitation.. try bleeding it 


I'm not sure I've got a spare working cluster for XF. Even if I did, it'd be my luck I'd get pulled over for a random logbook check and that'd be fun to explain.

Been thinking for a while now about doing what@Panko has done and adding in a couple of gauges in front of the shifter.

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2 hours ago, Mr Polson said:


 

 


From memory it has a bypass hole in it. I'd assume it's not blocked but guess I'll find out tonight when I take the housing off



I'm not sure I've got a spare working cluster for XF. Even if I did, it'd be my luck I'd get pulled over for a random logbook check and that'd be fun to explain.

Been thinking for a while now about doing what@Panko has done and adding in a couple of gauges in front of the shifter.

 

i haven't heard of many people in vic getting checked, but i guess with the less cars on the road due to semi lock down, the chances are much higher.. (i've been thinking i need to tidy up My van for this reason.. looks  a bit cop bait currently) we don't need to keep kms readings, can do as many as you like.
it certainly wouldn't hurt adding an additional gauge, even cars as "NEW" as EB-ED are having similar issues these days.. they are only 25yrs old.. (Mates XG was doing same, was the cluster recently, and i've had XFs do this 10yrs ago when i was driving them daily)

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Honestly, never seen that plastic bit, but if it came with it, I assume that it's supposed to be there. Doesn't make sense that you've want to block that hole with anything but there you go. I have seen that little valve before though.

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Now that you have a new one, and if it doesn't fix your problem, you could try removing that from your old one and just leave the little hole there. Worth a try?

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my escort does the same thing. 

 

it gets a bit above half way on the temp gauge, sometimes close to hot, then will rapidly drop. 
it has one of this little valves as well, and i think what it is, is the coolant passing through that little hole before its at the correct temp to open the thermostat, then eventually either gets hotter than normal temp, momentarily or creates an airlock where the temp sender is, until the thermostat opens and lets coolant flow as per usual, also dropped the pressure in the cooling system to its normal pressure (16psi in crossflows) 

Personally i dont like thermostats with that little valve, because of this reason. I noticed the moment i installed this type in the Escort it started doing it, but it has given the best results in the car so far. 
In my XF im pressure sure i run a thermostat which either has a little nick out of the side ring to allow coolant to always pass through, its a slow opening one where it opens under pressure from the pump, then opens fully when the coolant is at correct temp. but i know the XF doesnt run a valve in the thermostat, and it doesnt spike like yours does 

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Tested the new one before fitting.
Running the proper 89° thermostat (not 82° one like ALL aftermarket shops list).

DT14G is the Dayco part number for a 89° thermostat. Repco lists it as suiting Nissan XFN but not Falcons.

Got the new one in and went for a test drive, all seems well but tomorrow morning will be the real test.03611b75987aa337cee0395396fb7dc1.jpg

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The little plastic/brass thingy, is called a jiggle pin.

I believe it's to help break up any large air bubbles, when bleeding the coolant system.

 

To my knowledge, the factory crossflow thermostats didn't run a hole or jiggle pin.

The top thermostat housing bolt with the center bleeder screw, provided that function.

 

Factory fitted e-series 6cyl thermostats were 92c, made in UK by Waxstat, and had a jiggle pin.

The current e-series 'genuine' thermostats, are 91c, and don't have a jiggle pin nor hole - bad idea IMO, as they don't have a bleeder screw.

 

The factory e-series V8 thermostats (Motorcraft, made in USA etc) are rated at 89c and have a jiggle pin,

as they don't have a bleeder screw in the cooling system either.

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1 hour ago, Mr Polson said:

Ford workshop manual doesn't mention a jiggle pin, but does mention a bleed hole.
7d61bc24534a1c118a7d62f659821a8d.jpg


thats right i remember the one in my wagon now. 
it has that little bleed hole. 
 

others have a little triangle bit out the side 

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I always snip off the jiggle pin and just have the hole, and make sure it’s at the top, helps bleed the air out, and allows constant water flow so you don’t get spikes and troughs in the temp.

 

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thats right i remember the one in my wagon now. 
it has that little bleed hole. 
 
others have a little triangle bit out the side 
Don't remember what brand or where you got it?
Both Dayco and Tridon thermostats have the pin.
I always snip off the jiggle pin and just have the hole, and make sure it’s at the top, helps bleed the air out, and allows constant water flow so you don’t get spikes and troughs in the temp.
 
Does it affect the car getting to temp? It's a reasonably sized hole in the Dayco ones without a pin

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Looks like the factory stat, had a bleed notch on the inner moveable section?

I've never looked closely at that part, tbh.

 

I've got a Nissan XFN factory workshop manual,

and it shows that same notch.

 

My blue XE wagon, had an aftermarket e-series thermostat in it for some reason?

(with the extra bypass spring foot thingy and a bleed hole manually drilled in it)

I only found out, as it wasn't getting up to temp.

When I investigated, I found the thermostat was stuck open, with what looks like a tiny piece of casting metal/slag from the block.

 

After going through a couple of dud Tridon thermostats (sticking when opening, opening early/late, etc),

I decided to buy a Windsor V8 Motorcraft stat for the XE instead, as they're the same dimensions/temp rating (except have a jiggle pin).

 

Last time I bought Tridon ^^, they were re-boxed MotoRad stats - made in India I thought (could be wrong)...

 

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It’s something I learnt from my old man who is a “ older mechanic “.
1/8 hole in the main flange.

and to answer the question from Mr Polson, I find it warms up a little quicker and more evenly.

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Looks like the factory stat, had a bleed notch on the inner moveable section?
I've never looked closely at that part, tbh.
 
I've got a Nissan XFN factory workshop manual,
and it shows that same notch.
 
My blue XE wagon, had an aftermarket e-series thermostat in it for some reason?
(with the extra bypass spring foot thingy and a bleed hole manually drilled in it)
I only found out, as it wasn't getting up to temp.
When I investigated, I found the thermostat was stuck open, with what looks like a tiny piece of casting metal/slag from the block.
 
After going through a couple of dud Tridon thermostats (sticking when opening, opening early/late, etc),
I decided to buy a Windsor V8 Motorcraft stat for the XE instead, as they're the same dimensions/temp rating (except have a jiggle pin).
 
Last time I bought Tridon ^^, they were re-boxed MotoRad stats - made in India I thought (could be wrong)...
 
The one I pulled out is Tridon I believe. From what I know Tridon thermostats have the temp stamped on the face, Dayco ones have it painted on there.
Haven't tested it yet to check what the issue with it was.
It’s something I learnt from my old man who is a “ older mechanic “.
1/8 hole in the main flange.
and to answer the question from Mr Polson, I find it warms up a little quicker and more evenly.
Interesting. Pretty sure my old man has mentioned adding a bleed hole if they don't have one (another one of those "older mechanics").

Anyway the one I put in yesterday I took the jiggle pin out. And today it took way way way longer than normal to get to temp - only two bars by the time I got to work via the highway (6km drive).

Did order a new temp sender for the gauge in case that is also an issue - don't think I've changed it before in the wagon.

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