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07-09-2023, 08:15 AM | #1 |
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312 thermostat bypass hose plug question
1956 Mercury 312, I’ve read about the thermostat 312 bypass hose mod. I have a new 5/8” heater hose and a 3/8” plug with a 3/16” hole drilled into it. How do I screw the plug far enough into the hose to be able to get both ends of the hose on? It screws into the hose easy enough but once it’s inside the hose I can’t keep a wrench or socket on to continue screwing it in. I’m sure there is a simple answer but I’m scratching my head
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07-09-2023, 12:26 PM | #2 |
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Re: 312 thermostat bypass hose plug question
If it's the square extended-head type plug, hacksaw a screwdriver slot in the head. Install with dish soap for lube.
Terry
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"It don't take but country smarts to solve the problem" (Smokey Yunick) '41 Merc Town Sedan / 260" 8CM engine '66 Fairlane four door / "warmed up" 302 |
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07-09-2023, 12:43 PM | #3 |
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Re: 312 thermostat bypass hose plug question
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07-09-2023, 12:55 PM | #4 |
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Re: 312 thermostat bypass hose plug question
Maybe a foolish question, but what is the purposes of plugging the bypass hose??
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07-09-2023, 01:09 PM | #5 |
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Re: 312 thermostat bypass hose plug question
I believe the bypass hose allows the car to heat up faster, but once at running temp it continues to allow too much coolant to bypass the radiator. By plugging the hose, but leaving a small hole in the plug, the coolant will all mostly pass through the radiator leading to cooler temps. Most people who have done this mod are happy with the results from what I’ve read. I should also add that most will drill small holes into the thermostat along with this hose mod
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07-09-2023, 02:42 PM | #6 |
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Re: 312 thermostat bypass hose plug question
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A lot of this comes from the T bird side. The water pump spacer does reduce the efficiency of the pump, and the airflow thru the bird radiator seems to give a lot of us cooling problems. Especially stopped in traffic. But I know several guys who drive cross country and hot weather over 85 or so can cause cooling issues at 70. At least according to them. Drilling the thermostat, and using a high flow one (I think it’s a Chrysler part) helps to some degree. The drilled hole does more to help purge air from the system when you fill it. Talking about bird and Yblock overheating is like talking about “which oil”. Enough said. |
07-09-2023, 03:05 PM | #7 |
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Re: 312 thermostat bypass hose plug question
I would advise against doing this unless you do one more modification. And that is drilling some holes in the thermostat for additional water flow.
Why do I advise against it - I did the modification in my 56 Bird. What happened to me is the decrease in water flow made the temperature go way up at the begining until the thermostat opens. Scared the devil out of me. Maybe a bigger hole in the plug will suffice. I found out later that the person who did this successfully also made the holes around the perimeter of the thermostat.
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07-09-2023, 03:59 PM | #8 |
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Re: 312 thermostat bypass hose plug question
Is there a fan schroud? The typical problem is in traffic, not on the highway. This goes for most any car.
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07-09-2023, 04:54 PM | #9 |
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Re: 312 thermostat bypass hose plug question
“Talking about bird and Yblock overheating is like talking about “which oil”. Enough said.”
Haha very true! |
07-09-2023, 05:00 PM | #10 |
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Re: 312 thermostat bypass hose plug question
No fan shroud and as far as I can tell nobody makes one for a 56 Mercury. I would love to have one, as I think a shroud with a puller fan is ideal for cooling. I’m not actually overheating at all, but I do notice a slight temp increase when sitting at a light or traffic, and it will go down once moving. I think this mod is an inexpensive thing to try first before maybe doing a smaller pulley or different blade.
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07-09-2023, 05:01 PM | #11 |
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Re: 312 thermostat bypass hose plug question
[QUOTE=paul2748;2239188]I would advise against doing this unless you do one more modification. And that is drilling some holes in the thermostat for additional water flow.
Why do I advise against it - I did the modification in my 56 Bird. What happened to me is the decrease in water flow made the temperature go way up at the begining until the thermostat opens. Scared the devil out of me. Maybe a bigger hole in the plug will suffice. I found out later that the person who did this successfully also made the holes around the perimeter of the thermostat.[/QUOTE I definitely agree, I think if doing the bypass plug, doing the holes in thermostat is a good idea as well Thanks |
07-09-2023, 05:39 PM | #12 |
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Re: 312 thermostat bypass hose plug question
Learn something new here every day. Thanks!!
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07-09-2023, 07:26 PM | #13 | |
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Re: 312 thermostat bypass hose plug question
What is happening at a light is normal. It seems you have no problem. Let sleeping dogs lie. An easier fix would be a smaller fan pulley.
There are aftermarket shrouds around that most likely can be made to fit. Try Jegs , Summit or Speedway. Quote:
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07-09-2023, 11:41 PM | #14 |
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Re: 312 thermostat bypass hose plug question
Paul’s right about the heat reading on start up. I had an OT engine with no bypass hose do that. Changed the tstat twice before the light bulb came on. I finally figured out it didn’t happen if the heater was on. That provides enough water flow (at least in that one) to get hot water to the stat location. I added a bypass, small #4 AN hose and fitting. Solved it, I didn’t know about drilling the stat.
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07-10-2023, 08:24 AM | #15 |
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Re: 312 thermostat bypass hose plug question
True, but where I live it can be very heavy traffic at times. I’m thinking of worst case scenario. I looked up those universal shrouds and I think I can get one to work, thanks for the tip
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07-10-2023, 08:26 AM | #16 | |
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Re: 312 thermostat bypass hose plug question
Quote:
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07-10-2023, 08:01 PM | #17 |
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Re: 312 thermostat bypass hose plug question
If it's a hot day, what i do at a light is shift into neutral so the rev's go up which increases the flow. This doesn't work if you have a stick car.
QUOTE=Abchoppers;2239361]True, but where I live it can be very heavy traffic at times. I’m thinking of worst case scenario. I looked up those universal shrouds and I think I can get one to work, thanks for the tip[/QUOTE]
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07-11-2023, 09:50 AM | #18 | |
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Re: 312 thermostat bypass hose plug question
Quote:
I’ve done that trick as well, works good! |
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07-11-2023, 08:42 PM | #19 |
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Re: 312 thermostat bypass hose plug question
I got my shroud from Concourse parts, but I have a 57. I also have a 6 blade fan. I put a spacer on it, so that approx 1/2 the depth of the blades were int he housing. I had some of those that I likely bought over the years from SpeedwayMotors
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07-12-2023, 06:23 AM | #20 | |
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Re: 312 thermostat bypass hose plug question
Quote:
Thank you |
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07-13-2023, 03:30 PM | #21 |
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Re: 312 thermostat bypass hose plug question
You actually can make your own shrould...but it takes a little doing. There is a video I recall seeing years ago on youtube. Styrafoam you stack and shape. Then cover if with aluminum foil. Then lay fiberglass on it. After it cures ya pop it out, and spray paint it.
Doesn't look hard, but seems like a trial and error type of thing too. Definately not a 1 afternoon in the garage project. |
07-13-2023, 03:31 PM | #22 |
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Re: 312 thermostat bypass hose plug question
FYI, my 57 did not hold a lot of fluid with the factory radiator... I mean like hardly nothing.
Where are you? Does it get schorching hot there? |
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07-13-2023, 04:08 PM | #23 |
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Re: 312 thermostat bypass hose plug question
I’m on Long Island NY, gets into high 90’s here on some days. When I measure temps before and after the radiator it’s a good drop in temp, sometimes 25-30 degrees. I’m waiting on a high flow thermostat to be delivered, then I’ll investigate more because I have no idea what is in there now.
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07-15-2023, 06:58 PM | #24 |
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Re: 312 thermostat bypass hose plug question
So I ended up installing a 160 high flow thermostat after removing a 180 high flow. Drilled a couple of holes in it too. I also added the 3/8” plug into the bypass hose. Turned out to be an easy install with no leaks. Temps are about 10 degrees cooler overall. So far I like the results. Now come winter time I might be changing to a higher stat if I don’t get enough heat, but that’s a problem for another day. Thanks all for the suggestions and ideas
Ryan |
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