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Exnermobiles Samba Member
Joined: September 14, 2010 Posts: 64 Location: Finland
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Posted: Tue Jan 24, 2023 2:30 pm Post subject: 40 HP Stale Engine Thermostat Adjustment |
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Hello everyone!
I’m assembling my 40 hp stale engine and trying to understand the thermostat adjustment procedure described in the Bentley manual. I have followed step by step the procedure “Adjustment when Assembling Engine”:
When I complete step 4. the throttle ring becomes pre-loaded because the thermostat itself is pre-loaded in its bracket. Now the thermostat is not at all in its fully retracted state even when the engine is cold:
However, when heating the thermostat with a heat gun and when the thermostat becomes fully extended (touches the top of its bracket) the gap between the fan shroud and throttle ring is well within the given limits:
According to Bentley the gap should be between 25 and 30 mm:
Everything seems to be alright but I’m still wondering if the thermostat is supposed to be pre-loaded like that. When combining the pre-loads of the throttle ring spring and the thermostat I would not say that the throttle ring is “slightly pre-loaded” against the shroud. I think it is now more like “moderately pre-loaded”.
Can someone tell if this is normal or if something has gone wrong with my thermostat adjustment?
The thermostat is a NOS VW part:
_________________ 1962 Karmann Ghia Coupe
1958 Plymouth Belvedere Sport Coupe
1959 Dodge Sierra STW |
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pastellgreen Samba Member
Joined: January 06, 2012 Posts: 1036 Location: Germany
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Posted: Tue Jan 24, 2023 3:01 pm Post subject: Re: 40 HP Stale Engine Thermostat Adjustment |
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you made it right. The preload is not weak. |
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DeathRay64 Samba Member
Joined: February 03, 2019 Posts: 217 Location: Arizona
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Posted: Tue Jan 24, 2023 8:45 pm Post subject: Re: 40 HP Stale Engine Thermostat Adjustment |
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It has to be too much preload. Is the mechanism getting hung up on something?
It will eventually get as big as the thermostat bracket regardless of preload.
Edit: I thought your thermostat was being stretched open by preload but I think I misunderstood. _________________ Making VW's and America great again.
Last edited by DeathRay64 on Thu Feb 02, 2023 6:18 pm; edited 1 time in total |
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steven wardlaw Samba Member
Joined: January 13, 2012 Posts: 142
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Posted: Wed Jan 25, 2023 9:35 am Post subject: Re: 40 HP Stale Engine Thermostat Adjustment |
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Just make sure that when the engine is fully warmed that you have about an inch of clearance from the ring to the shroud. If it's over that you will hear the ring grinding away against the fan blades. I drive mine and check it hot. It doesn't take long after you shut down the engine for the bellows to start closing up the gap. |
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scottyrocks Samba Member
Joined: August 19, 2016 Posts: 2645 Location: Long Island, NY
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Posted: Wed Jan 25, 2023 9:55 am Post subject: Re: 40 HP Stale Engine Thermostat Adjustment |
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steven wardlaw wrote: |
Just make sure that when the engine is fully warmed that you have about an inch of clearance from the ring to the shroud. If it's over that you will hear the ring grinding away against the fan blades. I drive mine and check it hot. It doesn't take long after you shut down the engine for the bellows to start closing up the gap. |
Wait, you're saying that the ring will rub against the fan blades after it has pulled away from the fan? _________________ “If you care for a thing long enough, it takes on a life of its own, doesn't it? Mending old things, preserving them, looking after them – on some level there's no rational grounds for it.”
– D. Tartt, 'The Goldfinch' |
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pastellgreen Samba Member
Joined: January 06, 2012 Posts: 1036 Location: Germany
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Posted: Wed Jan 25, 2023 12:31 pm Post subject: Re: 40 HP Stale Engine Thermostat Adjustment |
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scottyrocks wrote: |
steven wardlaw wrote: |
Just make sure that when the engine is fully warmed that you have about an inch of clearance from the ring to the shroud. If it's over that you will hear the ring grinding away against the fan blades. I drive mine and check it hot. It doesn't take long after you shut down the engine for the bellows to start closing up the gap. |
Wait, you're saying that the ring will rub against the fan blades after it has pulled away from the fan? |
This is correct! |
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mukluk Samba Member
Joined: October 18, 2012 Posts: 6985 Location: Clyde, TX
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Posted: Wed Jan 25, 2023 12:40 pm Post subject: Re: 40 HP Stale Engine Thermostat Adjustment |
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How tall is the rubber bumper on the throttle ring, measured from the ring to its face which contacts the fan housing? _________________ 1960 Ragtop w/Semaphores "Inga" |
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EverettB Administrator
Joined: April 11, 2000 Posts: 69734 Location: Phoenix Metro
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Posted: Wed Jan 25, 2023 6:35 pm Post subject: Re: 40 HP Stale Engine Thermostat Adjustment |
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pastellgreen wrote: |
scottyrocks wrote: |
steven wardlaw wrote: |
Just make sure that when the engine is fully warmed that you have about an inch of clearance from the ring to the shroud. If it's over that you will hear the ring grinding away against the fan blades. I drive mine and check it hot. It doesn't take long after you shut down the engine for the bellows to start closing up the gap. |
Wait, you're saying that the ring will rub against the fan blades after it has pulled away from the fan? |
This is correct! |
I agree.
The ring rubs if it opens up too much.
This is something to check or ask if you are buying a used ring.
A lot of them have wear from rubbing in the past. _________________ How to Post Photos
Everett Barnes - [email protected] | My wanted ads
"Water is the only drink for a wise man" | "Communication prevents complaints"
Stop dead photo links! Post your photos to The Samba Gallery! |
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scottyrocks Samba Member
Joined: August 19, 2016 Posts: 2645 Location: Long Island, NY
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Posted: Thu Jan 26, 2023 12:06 am Post subject: Re: 40 HP Stale Engine Thermostat Adjustment |
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pastellgreen wrote: |
scottyrocks wrote: |
steven wardlaw wrote: |
Just make sure that when the engine is fully warmed that you have about an inch of clearance from the ring to the shroud. If it's over that you will hear the ring grinding away against the fan blades. I drive mine and check it hot. It doesn't take long after you shut down the engine for the bellows to start closing up the gap. |
Wait, you're saying that the ring will rub against the fan blades after it has pulled away from the fan? |
This is correct! |
How is this possible? _________________ “If you care for a thing long enough, it takes on a life of its own, doesn't it? Mending old things, preserving them, looking after them – on some level there's no rational grounds for it.”
– D. Tartt, 'The Goldfinch' |
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pastellgreen Samba Member
Joined: January 06, 2012 Posts: 1036 Location: Germany
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Posted: Thu Jan 26, 2023 5:20 am Post subject: Re: 40 HP Stale Engine Thermostat Adjustment |
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scottyrocks wrote: |
pastellgreen wrote: |
scottyrocks wrote: |
steven wardlaw wrote: |
Just make sure that when the engine is fully warmed that you have about an inch of clearance from the ring to the shroud. If it's over that you will hear the ring grinding away against the fan blades. I drive mine and check it hot. It doesn't take long after you shut down the engine for the bellows to start closing up the gap. |
Wait, you're saying that the ring will rub against the fan blades after it has pulled away from the fan? |
This is correct! |
How is this possible? |
I'm not a native speaker, for me too hard to explain.
Start your engine, grab the throttle ring and pull it out more than the thermostate would do. You'll see the result.
When you look at a sketch with a cut through the fan house, you see why this is possible:
The inner edge of the throttle ring touches the fan when too much opened. |
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scottyrocks Samba Member
Joined: August 19, 2016 Posts: 2645 Location: Long Island, NY
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Posted: Thu Jan 26, 2023 10:44 am Post subject: Re: 40 HP Stale Engine Thermostat Adjustment |
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Thank you for the visual.
I am actually still in the process of deciding on whether or not to do the thermostat system install myself, as I finally have all the correct parts.
I have seen the diagram that shows the adjustment for the throttle ring to be 20mm when fully in the out position. I had presumed that number was arrived at as a combination of the starting closed position, and the limited movement of the t-stat, itself, and the rest of the Rube Goldberg system that eventually moves the throttle ring. Stat expands, pushes up rod which pushes up and rotates rotates arm which rotates main shaft which moves ring out. Total distance = 20mm.
Basically, if the ring is more than 20mm out at max, it won't be closed all the way when the engine and t-stat are cold, yes?
Is this a 'safety' feature, as in - if you hear your fan hitting the ring, it's not closing all the way when the engine is cold so adjust it? _________________ “If you care for a thing long enough, it takes on a life of its own, doesn't it? Mending old things, preserving them, looking after them – on some level there's no rational grounds for it.”
– D. Tartt, 'The Goldfinch' |
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pastellgreen Samba Member
Joined: January 06, 2012 Posts: 1036 Location: Germany
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Posted: Thu Jan 26, 2023 12:08 pm Post subject: Re: 40 HP Stale Engine Thermostat Adjustment |
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scottyrocks wrote: |
Thank you for the visual.
I am actually still in the process of deciding on whether or not to do the thermostat system install myself, as I finally have all the correct parts.
I have seen the diagram that shows the adjustment for the throttle ring to be 20mm when fully in the out position. I had presumed that number was arrived at as a combination of the starting closed position, and the limited movement of the t-stat, itself, and the rest of the Rube Goldberg system that eventually moves the throttle ring. Stat expands, pushes up rod which pushes up and rotates rotates arm which rotates main shaft which moves ring out. Total distance = 20mm.
Basically, if the ring is more than 20mm out at max, it won't be closed all the way when the engine and t-stat are cold, yes?
Is this a 'safety' feature, as in - if you hear your fan hitting the ring, it's not closing all the way when the engine is cold so adjust it? |
Without the spring in action, the thermostat loosened, you adjust to 20mm. After tightening the thermostat and reinstall the spring, during a test with a heat gun the throttle ring should be open between 25 - 30mm. The spring causes a wider opening than the 20mm. The spring is strong and designed to 1. push the ring open in case the thermostat fails and 2. to avoid any play (and rattling) in the mechanism. It is the preload of the thermostat only that assures the throttle ring to be closed with preload against the fan housing (and this against the pressure of the spring) when the engine is cold.
Therefore: in my opnion, the op had done a good work and should leave the already correct working system as it is. |
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scottyrocks Samba Member
Joined: August 19, 2016 Posts: 2645 Location: Long Island, NY
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Posted: Thu Jan 26, 2023 1:42 pm Post subject: Re: 40 HP Stale Engine Thermostat Adjustment |
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Okay, so the initial adjustment is 20mm. Thanks! _________________ “If you care for a thing long enough, it takes on a life of its own, doesn't it? Mending old things, preserving them, looking after them – on some level there's no rational grounds for it.”
– D. Tartt, 'The Goldfinch' |
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Exnermobiles Samba Member
Joined: September 14, 2010 Posts: 64 Location: Finland
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Posted: Thu Jan 26, 2023 8:32 pm Post subject: Re: 40 HP Stale Engine Thermostat Adjustment |
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pastellgreen wrote: |
Without the spring in action, the thermostat loosened, you adjust to 20mm. After tightening the thermostat and reinstall the spring, during a test with a heat gun the throttle ring should be open between 25 - 30mm. The spring causes a wider opening than the 20mm. The spring is strong and designed to 1. push the ring open in case the thermostat fails and 2. to avoid any play (and rattling) in the mechanism. It is the preload of the thermostat only that assures the throttle ring to be closed with preload against the fan housing (and this against the pressure of the spring) when the engine is cold.
Therefore: in my opnion, the op had done a good work and should leave the already correct working system as it is. |
Thank you pastellgreen - this makes very much sense! I feel now more confident with the adjustment I have done.
The fact that the thermostat is constantly preloaded when the engine is cold is not highlighted anywhere in the service manual. _________________ 1962 Karmann Ghia Coupe
1958 Plymouth Belvedere Sport Coupe
1959 Dodge Sierra STW |
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Exnermobiles Samba Member
Joined: September 14, 2010 Posts: 64 Location: Finland
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Posted: Thu Jan 26, 2023 8:54 pm Post subject: Re: 40 HP Stale Engine Thermostat Adjustment |
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mukluk wrote: |
How tall is the rubber bumper on the throttle ring, measured from the ring to its face which contacts the fan housing? |
I hope this clarifies. _________________ 1962 Karmann Ghia Coupe
1958 Plymouth Belvedere Sport Coupe
1959 Dodge Sierra STW |
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52 split Samba Member
Joined: December 19, 2007 Posts: 149 Location: the best island in the world, vancouver island
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Posted: Fri Mar 01, 2024 9:32 pm Post subject: Re: 40 HP Stale Engine Thermostat Adjustment |
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thank you for your post, nice with pics. |
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Nitramrebrab72 Samba Member
Joined: November 10, 2018 Posts: 462 Location: France
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Posted: Sat Mar 02, 2024 12:54 am Post subject: Re: 40 HP Stale Engine Thermostat Adjustment |
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Beware if you have too much tension on the cable when cold you will prematurely split the diaphragm. Did you check the difference in height if any of the diaphragm in the freezer.???
Better slightly less tension than too much. |
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