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  View original topic: Observations on Tom Shiels thermostat housing for Subie
dobryan Mon Jul 30, 2012 12:14 pm

http://subaruvanagon.com/tom/Thermostat%20housingk.htm

Just wanted to post some of my observations on this.

Here is some back story. Several years ago I did a Subaru EJ 25 conversion of my '87 Westy. I sourced all the parts myself since there was not the great level of kits assembled like there is now. I used the yahoo group as a great resource. One of the items I installed was Tom Shiels thermostat housing. (This allows the thermostat feedback supply to go directly from the coolant manifold to the thermostat housing rather than going through the rear/front heater circuit.) I had a Scangauge on the dash so I could see detailed coolant temp info. I noticed that the engine operating temps were typically in the low 180's and would very gradually climb to about 200 when idling in the summer for a long period (stuck in traffic, etc).

Current story.... My current '87 Westy also has an EJ25 conversion which I moved from another Vanagon to this one. This conversion utilized the heater circuit to supply feedback to the thermostat (which is very typical it seems). I noticed that the coolant temps on this conversion were in the low 190's and seemed to have more fluctuation and at a quicker rate than my previous conversion. Last year I decided to retrofit the Tom Shiels thermostat housing to my current conversion. Here are the differences that I noticed after a year of operation:

-Normal operating temps were in the low 190's vs low 180's now.
-In the winter the temps would very quickly go from the low 190's to 200 (radiator fan would come on) when stopped at a light, now winter temps are in the low 180's and do not get above the low 190's at idle.
-In the winter the engine temps would be affected by the heater operation. If the heaters were on (cold outside) the engine would sometimes run in the mid to upper 190's while driving. No engine temp change (low 180's) with heaters on now.
-In the summer normal operating temps were in the low 190's but would quickly climb to the mid 190's and even 200 going up long grades. Now normal engine temps are low 180's and only climb to 190 on long climbs (even towing a 1000 lb trailer up a five mile grade).
-Max engine temps in both scenarios never got above 202.

So my observations are that in my case the engine didn't overheat under either scenario. But it seems that the Tom Shiels thermostat housing gives a better feedback loop to the thermostat. If the feedback loop goes thru the heater circuit some temp is lost (more in winter) thus making the thermostat think the engine is operating at a lower temp than it actually is. This is exacerbated at idle and in the winter when more temp drop occurs across the heater circuit.

I like the current setup since it gives me a little more piece of mind than the previous one. YMMV. :D

Franklinstower Mon Jul 30, 2012 5:57 pm

Hey Dobryan,
I use the Vanaru system which I think is a modified SC system that doesn't use Tom Shiels housing. My temps are typical 185-195 (this summer anyway) 195 being in the stop and go traffic. I have thought a lot about switching to Tom's method for a more consistent temp. Also I don't like the fact that you can't shut off the rear heater valve during summer travels with the Vanaru system.

What kind of changes did you have to make to swith to Tom's system?

thanks,

Paul

thummmper Mon Jul 30, 2012 11:13 pm

It was explained to me that without this 80 dollar device, it would overheat in the winter-- It has worked like a champ for me.

dobryan Tue Jul 31, 2012 5:09 am

Franklinstower wrote: Hey Dobryan,
I use the Vanaru system which I think is a modified SC system that doesn't use Tom Shiels housing. My temps are typical 185-195 (this summer anyway) 195 being in the stop and go traffic. I have thought a lot about switching to Tom's method for a more consistent temp. Also I don't like the fact that you can't shut off the rear heater valve during summer travels with the Vanaru system.

What kind of changes did you have to make to swith to Tom's system?

thanks,

Paul

No real difficult changes. I left the original cooling system in place and added the thermostat housing as per Tom's instructions. I plumbed a 1/2 line from just off the coolant manifold supply to the heater circuit into the housing to provide the feed.

Franklinstower Tue Jul 31, 2012 7:57 am

I have yet to over heat, 4+ years since the conversion. Even when I was in sun valley where the temps were -2 to 15. But I have never been particularily fond of using the heater circuit to supply the feed to the t-stat.

It is probably best to diamgram my system and compare it to Tom's newest version and go from there.

kalispell365 Tue Jul 31, 2012 8:49 am

i honestly think the sort of variances described in temperature are common in the subaru itself...this is a solution to a problem that doesnt exist.the subaru motor seems highly underrated with vanagon folks,these motors are bombproof.kind of like adding all these aftermarket guages to constantly monitor the oil pressure,etc.as a subaru technician i can tell you that these engines will literally last FOREVER if simply ran with coolant and oil up to par,these are no waterboxer...after being a part of the subaru conversion business over the last four years,i think the worst things that happen to the subaru conversions are from people comparing the systems to their old van motor and constantly trying to "improve" things.i have had several customers tell me they NEEDED a new oil pump on their subaru engine because of it being old.i have never in twenty years of subaru work seen an oil pump in any way fail...old thinking applied to a modern powerplant.these deserve far more credit than that,there are so many old 1990 legacys delivering mail,constant stop and go,on rural roads with no maintenence at 400k plus.i work on several,brake jobs and oil changes!

Jake de Villiers Tue Jul 31, 2012 8:51 am

Tom's thermostat housing is especially important if you want to use the heater in the winter. I struggled with this, running either too hot or too cold until I installed Tom's device. Now (like Goldilocks) its just right at all times of the year, under any conditions.

I wouldn't attempt a Subie conversion without one.

presslab Tue Jul 31, 2012 9:03 am

7 years ago I hooked things up pretty much the KEP way. I just leave the rear heater valve open, it doesn't emit any heat in the summer without the fan and it keeps the core from corroding due to stagnation.

I have good heat in the winter, nothing extreme but less than 20F, and the engine temps are just fine. Without the heaters blowing the temp needle is just below the LED, and with the heaters blowing the needle is just above the LED. That variation in temperature is minor. While climbing steep roads at low speeds in 1st gear, the needle goes well beyond that to about 7/8 full scale, at which the fan turns on, and that is also normal.

kalispell365 Tue Jul 31, 2012 9:20 am

presslab wrote: 7 years ago I hooked things up pretty much the KEP way. I just leave the rear heater valve open, it doesn't emit any heat in the summer without the fan and it keeps the core from corroding due to stagnation.

I have good heat in the winter, nothing extreme but less than 20F, and the engine temps are just fine. Without the heaters blowing the temp needle is just below the LED, and with the heaters blowing the needle is just above the LED. That variation in temperature is minor. While climbing steep roads at low speeds in 1st gear, the needle goes well beyond that to about 7/8 full scale, at which the fan turns on, and that is also normal.
CORRECT!
also,another misconception is that the subaru engine ONLY uses the heater feed to regulate the thermostat...one look at the block/water pump design will show this is inaccurate.if you are having heat up problems,there is a high possibility that you have an improper cooling system/air pocket,or a combination of both.
i have seen toms wiring work,he is a brilliant converter.i just know from experience,especially here where it is colder than anywhere else in the lower 48,that this iitem is unnecessary.all youve accomplished is several more junctions to leak.

Team WorldTour Tue Jul 31, 2012 10:31 am

@kalispell365-
While I agree with you 90%, I have to point you to one of my threads: H6 Conversion- My New Problem
Ultimately it came down to oil starvation.
With the new motor, I just dropped it in. No bolt-ons, nothin'! I hooked the cooling lines up to the custom made ones, bolted on the tranny, and re-installed the skid plate.
If you take my motor out right now, you could drop it straight back into a Legacy, no problems.
And the motor runs fine. The heater circuit is hooked to the original heater circuit, and the motor runs at a constant 92C. And in the winter (I live in Germany!), the heater ROASTS!
Sorry to say, but Toms T-Stat housing is (IMHO) not necessary.

kalispell365 Tue Oct 01, 2013 1:41 pm

I finally have seen a kennedy conversion,and must correct my ignorance...on the smallcar setup there is a fitting added onto the black heater pipe which goes to the water pump/thermostat bypass (black metal stock subaru heater line) on the stock subaru motor. this fitting has a small section of coolant hose that connects onto a fitting on the coolant manifold,therby creating a bypass. The kit that Tom has built does this for those folks thet have the kennedy style cooling setup.Otherwise,the rear heater loop is a MUST if you have the kennedy setup...otherwise the thermostat will not open and the engine will overheat!
I am sorry to anyone who has read this posting,has a kennedy setup, and been misinformed by my information.My ignorance to the Kennedy system is humbling...My apologies to Tom as well,his product is a necessity to the Kennedy kit,I now see...
Here is a link to a thread showing Bens bypass,which is the same as Smallcar.
Sorry!

http://www.thesamba.com/vw/forum/viewtopic.php?t=570430&highlight=subaru+rear+heater

dobryan Tue Oct 01, 2013 1:59 pm

Thanks for your post. :D

BTW it is not unique to Kennedy. Many of the conversions use a similar setup and may benefit from the kit Tom does. The main thing for those with a Subaru conversion is please be very familar with how the thermostat gets its feedback on engine temp and be sure to provide a reliable feedback loop for it...

dorje Tue Jan 08, 2019 1:50 pm

I just had the rear heater coolant lines tee'd together with a thin-diameter coolant hose. Provides plenty enough for a coolant bypass with a minimum of extra plumbing.

danfromsyr Tue Jan 08, 2019 2:42 pm

though I haven't used it yet, it was brought up in one thread. that there is a OEM subaru waterpump for the legacy 2.2 turbo that has the added port built in.
but then you'd have to remember that specific part/pump 4yrs later when you needed to replace it.

16CVs Sun Mar 22, 2020 10:48 am

So does anyone know the OE Subaru part Number for this pump? I think this is the OE Subaru Part number (21111AA065) .




Stacy

syncrodoka Sun Mar 22, 2020 11:37 am

You need a different thermostat cap to go with the different water pump style.
syncrodoka wrote: I got a different water pump for my other syncro that FrankenSubySyncro mentioned on another thread, it is from a '93 turbo legacy AISIN Part # WPF008.

The pump outlet faces rearward rather than down making the pump shorter. This is important for someone running the Tom Shiels t-stat housing adapter on a syncro as the adapter adds overall length to the water pump(without the adapter it is a non-issue) and severe mods need to be make to the skid plate as you can see here-

Since the pump was a extra outlet the adapter looks like it can be eliminated. The water outlet bolts are in a different position so that it is indexed incorrectly but I am sure the right one can be sourced.
Just a FYI unless someone knows a problem with this or a better solution. :idea:

syncrodoka wrote: Proof of concept from the post above.
The black timing belt housing is from a stock non-turbo 90 legacy not the '93 legacy turbo model that the water pump was designed for so it is a direct bolt up fit.


The water outlet elbow needs to come from something other than a standard N/A ej22. I pulled this one frome a SVX.


I don't know if or how it will work with different conversion mount systems but it looks like I can make it work with mine.

The advantage of doing something like this is like the post above shows you lose no ground clearance or have to make alterations to the skid plate but you gain the second nipple to route the cooling system like some recommend for cold weather cars to keep the cooling system and heat output working correctly.



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