Repairing a rotten lower Thermostat Housing

  1. xtriggerman
    These old car do not lac for surprise repairs! While in the process of swapping in an all aluminum Radiator, I thought I would check on the thermostat housing since it was dripping coolant. Mind you, this 1997 car only has 69K miles on it but as the saying goes, rust never sleeps.
    My first thought was just replace the entire thing but the only new section available is the top half that is the two 90 % ports. Those can be had off Ebay at $40 for OEM ( RH70 ) or like 18 bucks for a Dorman aftermarket. The bottom is only available as a junk yard take off and that's a gamble I would use as a last option. So, the big problem on my bottom end was the steel tank port. The inside was total sewer pipe rotten. To repair it, hack saw off most of the barb, leaving about maybe a 1/8th inch sticking out from the aluminum housing. My sawn off section crumbled up like paper under the plyers. To remove the section still left in the housing, used a section of hack saw and cut threw the steel tube, moving the blade in and out of the hole. Be carful not to cut into the aluminum beyond the steel tube wall. Once your threw, just grab whats sticking out with plyers and twist out the now loose pipe section. The tube is only a straight press in fit with no adhesives. The hole that's left is exactly the perfect size for a 1/2 x 14 NPT tap. The fitting needed is a male 1/2" NPT x 3/4" barb. I had a gas line fitting that I just turned the flare end threads off and made that end into a barb. Here you can see the freshly taped treads and the turned fitting.
    Just unreal how much those top end ports corroded! the bottom end one was only slightly corroded, THANKFULLY.... I was able to file and buff it out to my satisfaction.
    John_Carr likes this.


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  1. xtriggerman
    On a side note, NEVER try putting in a Fail Safe type thermostat in these cars DESPITE the fact that Auto Zone & NAPA list one for these cars. They have a built in air vent in the valve that will not let you fill the radiator with out over flowing the caped off res tank. Don't ask me how I know......
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