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Thermostat


John S

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Has anyone had this problem before. Simple job R&R thermostat. The new thermostat has a thicker outer ring at the  edge of thermostat. It is .022 thicker than the old one when I tightened the housing it cracked. I got a new GM housing and that one cracked too. That is when I compared the two thermostats and discovered the difference. I was using a torque wrench and only got to 15 ft lbs. Never had that happen before never even thought about checking. Both thermostats are NAPA brand premium. Anyone ever have this issue. Using a straight edge across the thermostat you can clearly see a larger gap between straight edge and manifold. Obvious why it cracked.

John S

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Hey John. It the new thermostat does not sit flush in the flange of the manifold obviously it is the incorrect thermostat. There also should be a gasket for the intake to waterneck. Some aftermarket waterneck use an o-ring instead of gasket. A groove is in the waterneck housing for the o-ring to sit. Usually a chrome neck. Have not seen any OEM necks for our vechicles with it. 

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 Correct but the problem I had was that the economy thermostat would fit fine the premium thermostat was thicker and of course when you tighten down the factory water outlet housing there is a gap between the housing and the intake that the gasket cannot make up so it cracks the housing.I prefer to stay away from the chrome ones with the O-ring they are very thin and cheaply made.  The only difference I noticed from a premium thermostat from an economy thermostat was the thickness they are both made for a 1970 Monte Carlo 350 but one evidently does not fit correctly. When I pulled the housing off there was no compression on the gasket and I used a felpro 35062 gasket.  Now I have an aftermarket aluminum housing that seems to be working but I'm using the economy thermostat not the premium . Parts made in China evidently are not made to the same standards as those made in the USA.     John S

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 When I get home and on my computer I have pictures of both thermostats with a caliper on them that way you can see the difference between them One I believe is .044 thick the other one is .066 thick

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The third picture is the new one on the left and the one out of the car on the right. Fourth picture is the new premium on left and the new economy on the right. the last two show caliper measurements premium and economy NAPA thermostats. The first and second pictures you can visually see the difference. As I said previously this is something you do not consider and  you don,t expect something like this until you crack a couple housing and investigate why.

John S

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I have heard of them cracking if its the wrong thermostat its not sitting in properly or even if there is a piece of dirt or old gasket on them. It is a flat gasket on oe type. I may still have the oe one I took off my car if you need one, I'll have to check for sure. the thermostat fits down into a groove in the manifold.

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 It has been thoroughly cleaned the gasket is the flat type. The problem I have is the  thermostat does not sit flush with the manifold when installed. As I stated this is a simple job  but every thermostat that I buy when installed in the groove it sits higher than the manifold I do not know if it's because of poor overseas quality but the one I had in there previously said made in USA . Unfortunately the part number is no good anymore I thought I was losing my mind over this until I let a couple of car buddies compare thermostats and they could see the difference One  thing for sure if I continue to do the same thing over and over again I'm going to get the same result. Far too much BS involved in a simple job. John S

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 I was able to find the same part number that came out of it put it in no problems. But while I was there I had the parts guy bring out two identical thermostats and I had one that I purchased the week before all three the same part number. I took my caliper and measured  the flange thickness on one was .034 on the second one .044 and on the third .051. Then I measured the flange diameter of the thermostat two of them were 2.125 and one was 2.117. I personally don't think that says much for quality control.  Oh well that's enough for this problem.  John S

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On 4/15/2019 at 8:58 AM, John S said:

 It has been thoroughly cleaned the gasket is the flat type. The problem I have is the  thermostat does not sit flush with the manifold when installed. As I stated this is a simple job  but every thermostat that I buy when installed in the groove it sits higher than the manifold I do not know if it's because of poor overseas quality but the one I had in there previously said made in USA . Unfortunately the part number is no good anymore I thought I was losing my mind over this until I let a couple of car buddies compare thermostats and they could see the difference One  thing for sure if I continue to do the same thing over and over again I'm going to get the same result. Far too much BS involved in a simple job. John S

 

On 4/14/2019 at 1:25 PM, MC1of80 said:

Hey John. It the new thermostat does not sit flush in the flange of the manifold obviously it is the incorrect thermostat. There also should be a gasket for the intake to waterneck. Some aftermarket waterneck use an o-ring instead of gasket. A groove is in the waterneck housing for the o-ring to sit. Usually a chrome neck. Have not seen any OEM necks for our vechicles with it. 

Hey Thomas not to keep beating a dead horse but I did use a depth mic the measure the recess where the thermostat sits in the manifold. There is a lot of corrosion and pitting there and it measures .040 left side and .034 rt side. A friend has an Edelbrock manifold and his measured .070. I'm sure that also has something to do with this issue. John S

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