thermostat leak
Thread Starter
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Junior User
Joined: Dec 2003
Posts: 55
Likes: 0
From: Winnipeg
thermostat leak
Yeah, I'm back again... woohoo 
I tried to replace the thermostat in my 67 f100, 300 6 cyl. Put it all together, with a new housing, gasket and thermostat. Put the thermostat into the housing, then gasket with silicone, then more silicone to the block and bolted it on. Filled the top tube to check for leakage, no worries. Put the rad hose on, start to fill the rad, whaooo, major leakage from the housing, I'm very certain it's not the rad hose or the heater hose.
In my mind, it has to be something in the mating surface of the housing and the block... as; in my thinking the block wont be filled with coolant until the thermostat opens.
Or am I incorrect? I have been wrong before, I think...
I tried to replace the thermostat in my 67 f100, 300 6 cyl. Put it all together, with a new housing, gasket and thermostat. Put the thermostat into the housing, then gasket with silicone, then more silicone to the block and bolted it on. Filled the top tube to check for leakage, no worries. Put the rad hose on, start to fill the rad, whaooo, major leakage from the housing, I'm very certain it's not the rad hose or the heater hose.
In my mind, it has to be something in the mating surface of the housing and the block... as; in my thinking the block wont be filled with coolant until the thermostat opens.
Or am I incorrect? I have been wrong before, I think...
Post Fiend
Joined: Jun 2002
Posts: 13,873
Likes: 3
From: Atlanta GA
The two main causes of leaking are:
1) thermostat is not seated in its groove
2) housing is cracked from being torqued down too tight. I have done this more then once to a Chevy
Lousy design, almost as bad as their starter shim idea.
Note that putting the thermostat in crooked and then bolting it on can crack the housing.
All you need for RTV is a very thin coat to hold the thermostat to the housing by using the gasket as a clamp (extra hand) and to seal minor imperfections. Most of the time you do not need it at all. If you do use RTV, it has to be made only for use with anti-freeze. Otherwise the antifreeze will destroy the normal RTV and the RTV just becomes a gap, not a sealer.
1) thermostat is not seated in its groove
2) housing is cracked from being torqued down too tight. I have done this more then once to a Chevy
Lousy design, almost as bad as their starter shim idea.Note that putting the thermostat in crooked and then bolting it on can crack the housing.
All you need for RTV is a very thin coat to hold the thermostat to the housing by using the gasket as a clamp (extra hand) and to seal minor imperfections. Most of the time you do not need it at all. If you do use RTV, it has to be made only for use with anti-freeze. Otherwise the antifreeze will destroy the normal RTV and the RTV just becomes a gap, not a sealer.
Post Fiend
Joined: Jun 2002
Posts: 13,873
Likes: 3
From: Atlanta GA
FWIW: If you have broken the housing that is bad news, the good news is a thermostat housing at Advance Auto Parts for your engine (Stant 31405 ) is only $8. The beauty of owing a I-6, besides being easy to work, is the parts are very cheap
:-)
:-)
Thread Starter
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Junior User
Joined: Dec 2003
Posts: 55
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From: Winnipeg
I'm from canada, the housing cost me $18 from NAPA... I got it all together, let's all go check out my other thread about the bizarre and strange behaviour of my temp gauge, wheeeeee
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Senior User
Joined: Jul 2003
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Stupid pot metal housings crack easily. Rtv should work good I used permatex #2 last time has not been an issue, but you may have a small crack in you housing from uneven tightening. first time i replaced mine i cracked two before i got it right. I had to tighten it down one half turn on each bolt at at a time to get t to tighten evenly. Tighten very, very lightly then run the motor if it leaks tighten a little more (half turn each bolt) then try running it again. this is the best way to tighten without cracking the housing.
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Laughing Gas
Joined: Jan 2002
Posts: 1,008
Likes: 1
From: Tucson
You might have the wrong gasket. I bought a new thermostat and gasket from NAPA. When I was putting it in I noticed the thermostat diameter was smaller than the one I was replacing and consequently did not fit tightly into the housing. In addition, the gasket, although at first glance looked right, was not, and leaked.
NAPA books indicate only one size thermostat for our trucks (smaller than mine). I think Ford changed thermostat sizes sometime during the 67-72 time frame. I ultimately got the right size from AutoZone. Anyhow, good luck.
jor
NAPA books indicate only one size thermostat for our trucks (smaller than mine). I think Ford changed thermostat sizes sometime during the 67-72 time frame. I ultimately got the right size from AutoZone. Anyhow, good luck.
jor
Thread Starter
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Junior User
Joined: Dec 2003
Posts: 55
Likes: 0
From: Winnipeg
yeah, it's fixed,
Edited to reflect the policy that this forum is for 67-72 Ford pickup tech information.
firedudecndn if you have an issue with the site owner or one of the admins, please take it up with them. It is my job to keep the forum on target with the site user guidelines.
What ever your political views are, you are welcome to them, and there are other areas of this site where they can be discussed.
John
Edited to reflect the policy that this forum is for 67-72 Ford pickup tech information.
firedudecndn if you have an issue with the site owner or one of the admins, please take it up with them. It is my job to keep the forum on target with the site user guidelines.
What ever your political views are, you are welcome to them, and there are other areas of this site where they can be discussed.
John
Last edited by jowilker; Aug 19, 2005 at 06:54 AM.