36 Series 40 Thermostat Housing

[Rock10]

What is the thermostat in this picture for? All we have left on ours is the shaft.

[Bloo]

Well someone thought it was for a 1938 or 1939 320ci straight eight (Century, Roadmaster, Limited) when they wrote on it. "1938-9 Big Ser" (big series). The part number on that tag might confirm or deny it if anyone has a parts book handy.

 

That is the thermostat housing, not the thermostat. You are looking at a bypass valve. Allegedly there is a problem with the design. People have been replacing that valve with a freeze plug with a hole drilled in it, to mimic Buick's own fix from a few years later. I don't know how big of an issue that is, but someone in here probably does.

 

The thermostat goes in that cavity in the bottom that is against the blue towel. It is positioned upside down right now compared to how it mounts on the engine.

 

 

[MCHinson]

If I am reading the part number correctly as 1321484 that is listed in Group 1.251 as a HOUSING, Thermostat 1941 after engine 4100930 on 40; 4105275 on 50; 4088516 on 60-70-90. 

[Rock10]

To clarify, that is not from our 36. Ours doesn't have the spring or valve, just the shaft. I wondered what it was for. Apparently someone has removed the mechanism from ours. What was the bypass function? Isn't that what the thermostat is for? Is it related to the heater? I'll try to post a pic later.

Thanks.

[Ben Bruce aka First Born]

The bypass is to allow a small flow of water through the ENGINE until the coolant is hot enough for the thermostat to open.  Otherwise, the thermostat, theoretically, would never see any heat and never open.

 

  Ben

[Rock10]

10 minutes ago, Ben Bruce aka First Born said:

The bypass is to allow a small flow of water through the ENGINE until the coolant is hot enough for the thermostat to open.  Otherwise, the thermostat, theoretically, would never see any heat and never open.

 

  Ben

So we need that part to operate correctly?

[37_Roadmaster_C]

@Rock10, That bypass was problematic on a good day. Buick had a service document that described how to remove the valve and install a fixed orifice kit.  I do not remember the exact specifications, but many people have done the same thing by driving a proper sized freeze plug with a hole drilled in the plug. I am thinking the hole was 1/4 inch or a bit smaller. The goal was, as @Ben Bruce aka First Born said above, to circulate a little coolant while the engine was warming up to allow the thermostat to open properly. I would recommend that you fix the problem by doing the Buick service fix.

Edited May 4, 2021 by 37_Roadmaster_C (see edit history)

[Rock10]

6 hours ago, 37_Roadmaster_C said:

@Rock10, That bypass was problematic on a good day. Buick had a service document that described how to remove the valve and install a fixed orifice kit.  I do not remember the exact specifications, but many people have done the same thing by driving a proper sized freeze plug with a hole drilled in the plug. I am thinking the hole was 1/4 inch or a bit smaller. The goal was, as @Ben Bruce aka First Born said above, to circulate a little coolant while the engine was warming up to allow the thermostat to open properly. I would recommend that you fix the problem by doing the Buick service fix.

Thanks. Does that shaft screw in or is it a press fit?

[37_Roadmaster_C]

9 hours ago, Rock10 said:

Thanks. Does that shaft screw in or is it a press fit?

 

@Rock10,  I am not sure. Mine was already cleaned before I was aware of the service documents. I am fairly sure that without the spring and cap it should basically fall apart. I would look it over very closely. If it is firmly in place someone may have done something to hold it in place. Brazed, soldered or some such.  There was an article on this somewhere on the internet. Maybe at the 37-38 Buick Club or in an old issue of the 37-38 Buick Club's: Torque Tube.  Hopefully someone will remember and chime in.

I found an article in the Torque Tube that has a good write up on normal operation AND a breakdown of the valve. It should help. Check Here:  https://drive.google.com/drive/folders/1W6Yr0rcgi3zyicwT_D4vo3duNt64XVq2

I know there have been discussions about the modification. It I find more I will post a link.

Edited May 4, 2021 by 37_Roadmaster_C (see edit history)

[MCHinson]

There are several ways to modify the bypass valve to prevent it from opening and allowing the coolant to bypass the radiator. You can remove the cotter key and remove all of the assembly except for the center brass rod. Most people cut the rod. Another option is to use a section of metal fuel line over the brass rod to prevent the bypass assembly from compressing. In my 1938 Buick Century restoration discussion on this site, I covered how I did the bypass conversion on that car. It would take me a while but I should be able to find a document that covers the typical repair. Essentially, it is just removing the bypass assembly, cutting out the brass rod, drilling a 1/4 inch or so hole in the center of an appropriately sized "freeze plug" and pressing the plug into the assembly to allow a small amount of water flow to reach the thermostat. This removal of the bypass valve prevents the spring loaded bypass valve from being able to open and cause the coolant to bypass the radiator.  

[MCHinson]

The earlier posted Torque Tube links are actually stored in my Google Drive. There are a few articles published over the years in the old 37-38 Buick Club Torque Tube newsletter issues covering the bypass valve. After the demise of the 37-38 Buick Club, some former members of the club started the 36-38 Buick Club. A much better resource on this subject than any of the old Torque Tube issues is an article that I published in the July/August 2016 Torque Tube II. Check out the following link for a comprehensive article on overheating and specific instructions on modifying the bypass valve:

 

https://drive.google.com/file/d/0Bwkvul_TyYjSMlRTMXhCQTNTQ1k/view?usp=sharing 

 

The comprehensive cooling system article starts on page 14 of that issue. The specific instructions on modifying the bypass valve are on page 16 of that issue. 

 

I guess now would be a good time for me to recommend that you should check out the 36-38 Buick Club at http://www.3638buickclub.org/ and consider joining the club. I think you would find membership in the club valuable and the newsletter that I have posted above is a good example of the type of technical information that you will find in the club newsletter as a member. 

[37_Roadmaster_C]

See the link in @MCHinson post above!!! I knew I saw it somewhere.  Thanks Matt for jumping in to help @Rock10 with this!!!

[Rock10]

Thank you all. I was able to cut off the remaining shaft and will install the drilled freeze plug tomorrow.

Another setback this evening. We discovered a crack in the block on the drivers side just under the freeze plug area. Looks like someone had tried to epoxy it before.

[37_Roadmaster_C]

Ouch!  I know that feeling well. The 320 in our Roadmaster had the same crack and someone had tried to weld it. Well, like a lot of cast iron welded repairs it cracked again just below the repair. That was it for that block. We got another very good block from Dave Tachney and rebuilt that one. All is good as the block from Dave came out of a 37 Roadmaster so the numbers are even right!!!

That crack is common as the block tends to have casting sand and junk in the water jacket and does not drain well. If this happens in cold winter areas and no antifreeze the block splits when it freezes.

Repairs are tough and good repairs, stiching, is quite expensive.

[Rock10]

4 hours ago, 37_Roadmaster_C said:

Ouch!  I know that feeling well. The 320 in our Roadmaster had the same crack and someone had tried to weld it. Well, like a lot of cast iron welded repairs it cracked again just below the repair. That was it for that block. We got another very good block from Dave Tachney and rebuilt that one. All is good as the block from Dave came out of a 37 Roadmaster so the numbers are even right!!!

That crack is common as the block tends to have casting sand and junk in the water jacket and does not drain well. If this happens in cold winter areas and no antifreeze the block splits when it freezes.

Repairs are tough and good repairs, stiching, is quite expensive.

THe car has sat for a while. We are going to try JB Weld. I'll try to post pics this evening.

[37_Roadmaster_C]

7 hours ago, Rock10 said:

THe car has sat for a while. We are going to try JB Weld. I'll try to post pics this evening.

If you are going to try JB Weld make sure you clean the patch area VERY well. I would start with a wire wheel and then a harsh solvent. One of the best for oil and grease removal is actually brake cleaner. Wheel, cleaner, wheel, cleaner and keep going until squeaky clean. Heat also helps to sweat oil out of the cast iron. You do not have to get it super hot to sweat out oils. A propane torch will work well. Another thing you should do before applying the JB Weld is to drill a small hole, 1/8-3/16 at the ends of the crack. Be careful to only drill into the water jacket. Cast iron is a bit like glass, the crack can continue to run with heat and cooling cycles. The holes at the ends of the crack will stop the run by relieving the end stress on the crack. Anyway, larger clean area and a good application of the JB Weld.

[Rock10]

Worked on it today. Got some grinding done and the 2 holes drilled.

[Rock10]

Also got the shaft cut out of the housing. Looking for a freeze plug. 1 1/2" is too small.

[37_Roadmaster_C]

@Rock10, looking at your pictures I have questions...  Was the crack welded in the past? It looks like a new crack beside an old repair. Next, are there already holes drilled or is it just an illusion in the picture? Finally, I would go after that crack a bit more with the wire wheel and possibly even a light touch with a grinding wheel to get clean metal within the crack a tiny bit. You will most likely have a working repair with the JB Weld. Make sure to work the JB down into the crack to help seal and hold it in place. On these old cars the cooling system was not pressurized so that helps a lot with this.

On the thermostat housing the freeze plug is normally pressed into the smaller opening closer to where you cut the rod. Either will work so just go with the plug you find that fits!

Keep going, you will get there 😀.

[Rock10]

3 minutes ago, 37_Roadmaster_C said:

@Rock10, looking at your pictures I have questions...  Was the crack welded in the past? It looks like a new crack beside an old repair. Next, are there already holes drilled or is it just an illusion in the picture? Finally, I would go after that crack a bit more with the wire wheel and possibly even a light touch with a grinding wheel to get clean metal within the crack a tiny bit. You will most likely have a working repair with the JB Weld. Make sure to work the JB down into the crack to help seal and hold it in place. On these old cars the cooling system was not pressurized so that helps a lot with this.

On the thermostat housing the freeze plug is normally pressed into the smaller opening closer to where you cut the rod. Either will work so just go with the plug you find that fits!

Keep going, you will get there 😀.

There were signs of some previous repair but not a weld. Those are the holes I drilled today. I am thinking of tapping them and using epoxy on either stainless steel or brass screws. Yes, still have work to do on the cleaning but the front hole hit water still in the block and kinda washed me out for the day.

So the freeze plug goes into the smaller hole? OK. New search.

[37_Roadmaster_C]

Oops, me wrong, I went back to Matts post and looked at the picture and it is the bigger opening.  Its the pits to be getting older....  As for the crack. It looks to me that your holes may not be all the way to the ends of the crack. They need to be at the ends to relieve the stresses. As far as tapping and screws it is not needed. Just plug with the JB Weld unless you are thinking of stitching the crack. If you are I will leave the research to you. It is the way to fix cracks in cast iron, but it is a bit of an art and I am most definitely not an artist...

[Rock10]

2 minutes ago, 37_Roadmaster_C said:

Oops, me wrong, I went back to Matts post and looked at the picture and it is the bigger opening.  Its the pits to be getting older....  As for the crack. It looks to me that your holes may not be all the way to the ends of the crack. They need to be at the ends to relieve the stresses. As far as tapping and screws it is not needed. Just plug with the JB Weld unless you are thinking of stitching the crack. If you are I will leave the research to you. It is the way to fix cracks in cast iron, but it is a bit of an art and I am most definitely not an artist...

OK, back to the big hole.

I'll check again tomorrow for the length of the crack. No stitching! I did research it. I just thought the screws would provide a good anchor at each end. Since I'm working upside down and JB Weld is a little saggy. I was afraid it wouldn't stay in the holes that well. Was planning on several coats with sanding in between. BTW, what is the purpose of the "vent" that goes into that rectangular space toward the rear of the block?

[37_Roadmaster_C]

That is the place for the crankcase vent tube, or "draft tube". It is just a tube about one inch in diameter connected to a metal box that matches the casting. I think there is a filter material in the box to keep dust and dirt out of the crankcase. It mounts with the tube down and when driving the air flow causes a slight vacuum keeps the crankcase clear of vapors and moisture. In modern engines it is done with the PCV valve and hose. PCV, Positive Crankcase Ventilation. If you do not have it ask on the forum or again, call Dave :).

On the crack and holes...  It might be helpful to get some big syringes and maybe big needles, 14 ga would work well I think.  Cut or grind the point off the needle and flatten the tube a bit to fit into the crack. You might just be able to heat and flatten the plastic tip of the syringe and not need the needle. Use this to force the JB Weld well into the crack. This would help seal and also help hold it tight. As you go along filling the crack you could use some tape to hold the JB in place until it begins to set. Once firm, remove the tape and give it a light wipe with cleaner to remove the tape adhesive then sand and apply more if needed.  Just a thought. Syringes are available at pharmacies, vets and some farm supply stores.

Edited May 6, 2021 by 37_Roadmaster_C (see edit history)

[Rock10]

We have the tube on the other side by the distributor. This one is on he manifold side and had a vent like piece bolted on it. I'll see if I have a pic.

Good idea on the syringe. I think I have some left over from doggy medicine.

 

[MCHinson]

Yes, the road draft tube is on the passenger side of the engine. The other vent is on the driver's side. Both of them are involved in the crankcase ventilation system, but I don't recall exactly what the air flow pattern is. If you look in your service manual, I suspect you will find a diagram that shows the air flow pattern. 

[Rock10]

4 minutes ago, MCHinson said:

Yes, the road draft tube is on the passenger side of the engine. The other vent is on the driver's side. Both of them are involved in the crankcase ventilation system, but I don't recall exactly what the air flow pattern is. If you look in your service manual, I suspect you will find a diagram that shows the air flow pattern. 

I suspected that but not sure how they are connected.

[37_Roadmaster_C]

Thanks again Matt........  I try to help and seem to be 50-50 with confusing things. At least I can hide my own Easter eggs...............

[Rock10]

Final cleanup tonight. Ground out past crack. Drilled several new holes to anchor the JB. Sanded with 60 grit, heated it up with the torch,blew it out with the compressor and wiped it down with acetone. 

Used an old syringe to try to inject the epoxy into the holes and smoothed it out with an acid brush. Will sand tomorrow and apply a second coat.

Pics are before the cleanup. I followed the crack with a carbide grinding tip.

 

[37_Roadmaster_C]

Sounds like an EXCELENT first pass!!  You will have a very good chance of it sealing and holding. Do not be afraid of spreading the JB out wider as you continue. The more surface area you have the better the hold and seal, within reason of course.  Great job!!

[Oldtech]

21 hours ago, 37_Roadmaster_C said:

Sounds like an EXCELENT first pass!!  You will have a very good chance of it sealing and holding. Do not be afraid of spreading the JB out wider as you continue. The more surface area you have the better the hold and seal, within reason of course.  Great job!!

Agreed! 🙂

[Rock10]

Final of 4 coats with sanding in between. Applied with an acid brush. Hoping to get it started for the first time this weekend, but having some carb and spark problems.

The fun never ends.

 

[Rock10]

One more

[critterpainter]

On the thermostat housing, the quick way to install a soft plug is to place a 1 1/2" ? dished plug with a 1/8" or so hole in it  into the Short Hose between the water pump and the thermostat housing.  

[Rock10]

2 hours ago, critterpainter said:

On the thermostat housing, the quick way to install a soft plug is to place a 1 1/2" ? dished plug with a 1/8" or so hole in it  into the Short Hose between the water pump and the thermostat housing.  

I used a 1 1/2" freeze plug and epoxied it into the housing. Drilled a 5/16" hole.

[Rock10]

HEY! It runs! A few problems still, but IT'S ALIVE! 

[37_Roadmaster_C]

Good Job!!!  Now the fun begins....  Don't worry to much about the strange rattles and creaks......  Oops, did not mean to get you thinking about ghosts 🤭.

[Rock10]

😂

It was amazingly quiet. We didn't know it had started at first. A little lifter noise once it warmed up a bit and LOTS of smoke. But smooth and steady idle. Even with the leaky carb.

Edited May 15, 2021 by Rock10 (see edit history)