Thermostat questions and study

Discussion in 'V8 Discussion' started by GEN 3 SHO FAN, Jun 6, 2019.

  1. GEN 3 SHO FAN

    GEN 3 SHO FAN SHO Member

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    I finished yesterday my waterpump et thermostat replacement. Thermostat isn't too difficult to change but the pump is. I found some bolt holding the pump loose (3 of the 6)... The gasket of the thermostat was falling apart too. When I retreived my thermostat, I realized that it wasn't the original one. The original had only one spring (and only one moving part on) and mine had 2.

    I'm questionning myself on aftermarket thermostat, they have some kind of tail with a restraining part at the end (to lower the thermal choc on parts). Considering our engine have a reverse flow cooling and completely different hoses setup, I'm wondering if this tail (back plunger) can restraint too much the flow and keep the temp higher in city (when the T-stat is always open) ?

    If yes, it is possible to cut this tail on aftermarket ones to keep the shape of the original one as it will be difficult to find this ford part now ?

    Some have a taller "door" too, I think it may also play on operating temp in city .

    I put a 170 degre rather than a 180 to try as the motor stay hot in city and traffic 1/2 and 3/4 of the gauge). But I know that I'm not going in the good direction (I kept the old one too.)

    Any thought or suggestions ?

    Thanks,
     
    Last edited: Jun 6, 2019
  2. GEN 3 SHO FAN

    GEN 3 SHO FAN SHO Member

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    After some reflexions, the car will not leave the garage until I found a better T-stat.

    Our SHO, more than any normal car, is like an overclocked computer. It's must be cooled efficiently if you want to truly enjoy his power (even more if you did some tricks on it). On computers, we may have "bottlenecks", a weakness caused by a single part that will slow down the entire computer. And ours, are like an overclocked Intel I7 processor placed in small tower case.

    After some comparisons between some brands, here is my reflections. Some T-stat could be more restrictive to the SHO cooling system. Design in T-stat could be important at this point OMHA. Even wide open, the t-stat could create a bottleneck.

    Here is the one I put. (Motorad 281-170) (Edit : not anymore)
    t-stat Motorad 281-170.jpg

    The better I found for the moment. (Gates 33868-S /33868) It also have an higher price.

    t-stat Gates 33868S.jpg

    I will be very curious to have advices on that... (upgrade ?)

    Have a good day,
     
    Last edited: Jun 19, 2019
  3. gamefanatic

    gamefanatic SHO Member

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    The Gates is headed in the right direction for the main opening, but still looks cheap. The aftermarket versions of the T-Stats with the 3 all towers have a smaller than OEM opening, reducing flow and ultimately allowing water to heat soak.

    I have also been looking for an OEM style and found that Toyota 4 runners have the same T-Stat. Might be able to get an OEM from one of them. I just haven't chased one down yet.

    Mishimoto makes one that is a lifetime warranty, but is a 160°F. That's okay for summer, but experience has shown that to be a little to cold for winter to get things warm inside the car. Its the one for the Toyota MR2.

    https://www.mishimoto.com/toyota-mr2-racing-thermostat-02-05.html
     
  4. GEN 3 SHO FAN

    GEN 3 SHO FAN SHO Member

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    The stock T-stat is reputed to be very reliable over time according to veterans here. Let see how the stock one was made in comparison with an aftermarket... (It's an RT-1114 from Motorcraft)
    SHO thermostat 2.jpg
    Seems solid but not so efficient with this small opening...

    But you have a good point Gamefanatic. Our SHO share this part with many japanese cars. I have not searched on this side. I rode long time ago, that some Mitsubichi had the same part too.

    Why are you saying these aftermarket are weaker ? How they will broke ?
     
    Last edited: Jun 7, 2019
  5. gamefanatic

    gamefanatic SHO Member

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    Actually your's doesn't have the backing. Not sure why that is. The point of that back is to close off the flow to the bypass once the car is up to temp. This generally means that flow may go in two directions. I'd have to pull out a diagram, as it's been a while since I have looked at the flow. My understanding of the backing is to help warm up the water with a closed loop before the main T-STAT opens. The second reason is to prevent clogs (not typical of aluminum engines), which is actually an issue of the OHV versions where they came up with a fix if the heater core got clogged it would bypass it.

    Your OEM does look to have a smaller opening than my OEM. Hard to tell with the side shot, but mine has an opening closer to the Gates style, but the inner opening is larger. The biggest flaw in our versions is the rubber inner insulator which is typically where it may fail.

    Yeah, I have valve seals from a Subaru. Can't remember the model off hand.

    Not really saying they are weaker, just made with lesser attention to detail / quality. The Gates has a flat stamped out for the rear, but OEM is curved along the edges and only enough to hold the spring in place. Similar quality issues to computer case designs of the early 90's. Always fun making regular blood donations back then...

    I'll post a picture of the 4-Runner T-STAT later.
     
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  6. GEN 3 SHO FAN

    GEN 3 SHO FAN SHO Member

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    You're right the major flaw is the rubber inner insulator. Mine was falling apart and must be replaced at 135 k.

    The back plunger is close to the main cooling hoses of the heads and also a smaller one returning coolant from the bloc (starts between the heads). This last one seems more affected by this plate according to another picture that I have only in my book (page 03-01C-92 of the SHO supplement). Watching at this images, I'm wondering if the back plunger isn't affecting badly the coolant flow to the head and bloc and could be my culprit...

    If, as you said, the back plunger is there to help heating the opening spring (makers all saying it's for reducing thermal choc...?), there is enought heat there to give the info to the spring... (best example is the stock one working without).

    SHO Cooling.jpg

    v8 sho coolant reverse flow system.jpg

    I will retreive the one in place (170F with a small mouth). I bought another one, a Gates at 180F with a bigger mouth, it will be here tonight (thanks Amazon Prime). I will cut his "backplate" from it and I will watch is the engine behavior in the next days.
     
    Last edited: Jun 7, 2019
  7. GEN 3 SHO FAN

    GEN 3 SHO FAN SHO Member

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    I think I got it...

    The smaller hose returning hot coolant from the heads split in 2 hoses. One is returning cooling to rad, the other (33% of the hot coolant) is going directly on the back of the T-stat to heat his spring...

    The back plunger is blocking a great part of the information in heat changes and redirect the hot coolant to the pump and others components.

    It's clearer on my 3rd picture. Watch the hose going directly on top of waterpump on 1st picture. Lower in the assembly, it makes a 90 decree and arrive right on the back plate of T-stat.

    The T-stat will receive sooner or later the info but will needs more reaction time. Meanwhile the engine become more and more hot...

    My engine never goes in red area but goes easely in high range each time (3/4) even if I don't asking so much.

    I believe these back plungers aren't designed for a reverse flow cooling system.
     
    Last edited: Jun 7, 2019
  8. stephen newberg

    stephen newberg Moderator Staff Member

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    Mine is the stock one that came with the car. Still works fine 20 years + and 200K+ down the road.

    pax, smn
     
  9. GEN 3 SHO FAN

    GEN 3 SHO FAN SHO Member

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    Yes, the stock one seems very reliable (and don't have a back plunger). Sadly, mine was replaced by a previous owner by some kind of ACDelco according to his shape.

    Waterpump seems also very reliable. At 143K, it stills perfectly fonctionnal and bearing still good too (no corrosion, no damaged propeller, no leaking). The only thing was some bolts was loose enough to turn them with 2 fingers...

    Edit : after I cleaned it, I saw that there is some letters painted on it, saying it was replaced by a used one.
     
    Last edited: Jun 19, 2019
  10. GEN 3 SHO FAN

    GEN 3 SHO FAN SHO Member

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    Ok, I made 2 runs with the car and I can see some changes when rolling in city (in summer).

    First, Amazon send me something different from what I have bought. (&?*%?/*&). I decided then to re-put the older as he works correctly but I saw his plunger back to give it the same shape as the stock one (and doing this will give me the best comparative). As it was a mild metal it took maybe 15 sec to chop the tail. I inspected carefully and retrieving the plunger back doesn't affect the solididy of the T-stat.

    Now, when rolling in stops and red lights area, rather than climbing to 3/4 stay there most of the time with some signs of exhausting, it will stay at 2/3 most of the time and will have rares peaks at maybe 3/4. The engine also seems to cool down much faster. It will return to 1/2 after some second of rolling.

    It is not perfect as we are not in hot summer day here but it's better. Maybe a colder t-stat can me help me too at this point.

    To those who have heat prob, I recommend to make a check up there and see if your T-stat is stock or not and find something without a plunger back.

    I will try to add the image showing how the hot hose is pitching cooling on the back of the T-stat. Pretty sure the plunger back is interfering in the communication between engine heat and the T-stat now.
     
    Last edited: Jun 9, 2019
  11. SHOZ123

    SHOZ123 SHO Member

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    Your pic of the OE one does not look like the OE I have though it may be the angle. The OE defiantly has a plate on the bottom this is for when the t-stat fully open will close the thermostat bypass, usually around 230F or so.
    G3 SHO OE t stat.jpg
    G3 SHO OE t stat 2.jpg
    G3 SHO OE t stat 3.jpg
    G3 SHO OE t stat 5.jpg
    G3 SHO OE t stat 6.jpg
     
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  12. rpettey

    rpettey New Member

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  13. rpettey

    rpettey New Member

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    The thermostat in the gen 3 v8 is exactly the same as the toyota oem 90916-a3003.
    I was surprised to see this while replacing the thermostat on my 2000 es300. Part number will cross reference to both engines.
    Visual comparison also confirmed the are exactly the same.
    I have an original gen 3 tstat, side by side, exactly the same as the toyota.

    I suspect yamaha had a hand in this.
    From what I have found, the gen 3 v8 is the only ford engine to use this thermostat .

    So, there is no problem getting an oem thermostat. Just get the oem toyota 90916-a3003.
     
  14. gamefanatic

    gamefanatic SHO Member

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    Here is the Toyota 4-Runner. Like others have noted its likely from the same manufacturer, but stamped for the individual auto-makers. This one is actually 82°c and has the rear blocking plate which engages when the T-Stat opens. This one also had the inner seal fail.

    20190608_105207.jpg 20190608_105150.jpg
     
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  15. GEN 3 SHO FAN

    GEN 3 SHO FAN SHO Member

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    God... I thought this case was closed... but thanks to help me with that.

    Just to make things clear. The T-stat I have in place similar to the 2nd photo (AC Delco one). I cannot say if its a 180F because there is no mention on it but according to the needle, it can be one.

    Ok, the T-stat that all of you you're speaking about is almost the same as the Gates one that Amazon send me (but different from the photo on the puchase page). :S He was so big that I thought it was the wrong one...

    Like I said on others posts, I'm collecting photos of SHO original parts to have comparative and reference when time comes to find one. I have 2 cases where 2 original T-stats were for sale on e-bay. I kept the pictures and theirs Ford parts #.

    One was from 96 and one from 98. I presumed that Ford revised this part for 98 according to the part # but no visual difference between them... The 2 don't have a back plunger.

    I will keep you on the touch and put my photos here soon. I put here what I remember but I will correct it with photos.

    F6DZ-8575-AA (1996) / RT-1114
    F8DZ-8575-AA (1998) / RT-1137 (197F ?)

    Someone can give me some feeding on behavior with a stock one ?

    My temperature behavior (with a weather of 70F) :
    rolling freely : needle between 1/4 - 1/3
    at a red light : 1/2 going up to 2/3
    stop and go (red lights and stops) : 2/3, some peaks at 3/4 if I ask some growls

    It seems normal to you ?

    For Toyota, I'm not really surprised, back in the days, Yamaha also have partnership to work on Celica engines. Yamaha developed their sport engine with exactly the same engine but with 80 hp more IIRC... (around 2000)

    Thanks, I will come back this evening with additionals info,
     
    Last edited: Jun 19, 2019
  16. SHOZ123

    SHOZ123 SHO Member

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    Until you can get some OBDII data then the gauge is only there for the feels. They are not accurate to use for diagnosis unless it's stays in the cold or goes into the hot. Anything in between is dumbed down so people don't get excited about the needle moving all over.

    That being said I don't think my needle ever move much once it got warmed up.
     
  17. GEN 3 SHO FAN

    GEN 3 SHO FAN SHO Member

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    Good to know. And at where your needle was pointing at most of the time (pecfectly in the middle at 1/2) ?

    Ok I understand, the backplate is there to close the t-stat bypass to help t-stat to let more fresh coolant entering the engine ? If it's correct, mine wasn't working correctly. At 3/4 the engine seems exhausted and was loosing power (around 25% maybe).

    Thanks for helping me,
     
    Last edited: Jun 10, 2019
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  18. SHOZ123

    SHOZ123 SHO Member

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    Whatever it read, you don't know what it reads.
     
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  19. gamefanatic

    gamefanatic SHO Member

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    Its true that the tempsender going to the dash could also be an issue. There are two sensors one for your dash gauge, and one that goes to the computer. Best to match them up.
    I know I replaced mine recently because it was reporting erratically. Of course I got the wrong one, so now it shows normal temps at about 3/4 of the gauge...
     
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  20. GEN 3 SHO FAN

    GEN 3 SHO FAN SHO Member

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    My temp sensor is almost new (1 year), I changed it when I was searching for this heat issue.

    (The SHO have only 1 sensor, it's the SLO that have 2 IIRC. I double checked recently and I never found the 2nd. They are side by side on SLO. They are the same, aftermarket can be exchanged from one to the other as they are made without the special plug with a tooth.)

    For the T-stats, here is the schematics on my book I spoke of (the 3rd picture).
    waterpump driver side 2.jpg

    Here is the photo that lead me to mislead you. :S (Sold as a t-stat for 96 SHO on E-bay.
    SHO thermostat 1.jpg

    Notes :
    F6DZ-8575-AA (1996) / RT-1114
    F8DZ-8575-AA (1998) / RT-1137 (197F for SLO ?)

    Here is the Gates I received...
    Gates 1.jpg Gates 2.jpg
    Seems a in-between the AC Delco and yours from Toyota. The spring is also really big on that one.

    This one was already on the SHO and I re-put it in place without his tail and a new seal. The main spring is shorter than Toyota and Gates.
    Ac delco.jpg

    I must admit that I like the new engine behavior. I take the car to work in some traffic in city and the engine stay cooler. It seems like it have some more endurance when the traffic starts to roll, seems a bit more nervous in stop and go too. By some time in the past we were able to feel heat at our feet without asking for it...

    I didn't had the chance to try it at WOT or on heavy load to see if it will react correctly. Can I have issues with a t-stat without a tail ? (I'm not very interested to go there for a 3rd time...)

    If isn't dangerous, I will report back when I tryed some heavy load situations.

    From what I see now, it could be a great cooling /maintenance upgrade. (?) I didn't replace anything else that can affect the temperature of the engine, sensor is almost new and even the T-sat is the same. Then the engine will also keep his minimal 180F to work.
     
    Last edited: Jun 11, 2019
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