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Old 07-31-2015, 06:47 AM   #1
catalinajack's Avatar
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Lehman 120 Thermostat Replacement

Okay, I searched the forum before posting this. I need to replace the the temp senders which are difficult (near impossible, I think) to remove without the expansion tank removed. I would replace the thermostats while I have them removed but, despite being a pretty good mechanic, I cannot figure out how to remove the tanks. I have seen posts stating that doing so, to replace the thermostats is easy, but I just don't see it. There is a flange on the bottom of the tanks with studs and nuts. Remove at this point? How? Doesn't look like there is enough clearance to get an open end wrench in there. Help!!

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Old 07-31-2015, 07:41 AM   #2
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Mr. cj. Yup, that's the flange. I had to alter an open ended wrench (bend and grind if I recall) many, many years ago to actually FIT in there but I can't remember the final configuration of the "specialized" tool. It IS doable and actually quite easy with the right "tool". 1/2" or 9/16"...


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Old 07-31-2015, 07:53 AM   #3
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An extended crows foot wrench?

But often they are as thick or thicker than a regular open end.
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Old 07-31-2015, 09:31 AM   #4
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There is very little clearance. Just a standard open end wrench, and depending on how your engine is installed (ie how close to a bulkhead and overhead clearance) you may have to flip the wrench a lot and won't get more than 1/4 turn with each rotation.
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Old 08-09-2015, 09:26 AM   #5
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Indeed it is a bit tricky to remove the tank but not as hard as one might think. You just need a bit of patience to unscrew the nuts. Once it's removed it is a 2 minute job.
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Old 08-13-2015, 10:22 AM   #6
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Lehman Thermostat replacement

Long ago I modified a wrench to remove the injection pump from the 5.7 diesel that GM punished unsuspecting owners with. I got rid of the car and the wrench has been unused until recently. It is a perfect fit for removing the nut from the Lehman head tank. Hopefully the Lehman will be easier to live with than the 5.7 was.

Dan Girvan
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Old 08-17-2015, 10:01 PM   #7
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I purchased a set box/open end wrenches a Harbor Freight just to get one wrench that I could grind the shoulders off on the open ends and ground down the box end all the way around. Fits and works perfectly. You don't need the thick shoulders for those 2 small bolt. Spray on a little color and save it for a dedicated wrench.
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Old 08-20-2015, 07:43 PM   #8
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There is just enough space to get the nut part way up the stud. At that point you can raise the tank off of the head to finish removal of the nuts the rest of the way.

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