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Water pump bolt torque, and how not to strip the threads?


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1994 Subaru Legacy

When I removed the water pump, I found a few of the bolts were loose - two were finger tight/lose and I just unscrewed them with my hands. I found this to be very disturbing because I was the one that installed the pump several years ago. I really don't remember if I torqued them or just guessed at it.

 

So anyhow fast forward to installing the new pump. The bolts are small and I've developed a healthy appreciation for stripped threads. So my questions:

 

What is the torque for these bolts, and any advice to 1) keep the threads from stripping, and 2) keep them from coming loose again?

 

LIkewise, any idea as to torque for thermostat housing?

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you need to get a manual, either a haynes which not many folks like or down load a free one from:

 

http://legacygt.com/forums/showthread.php/second-gen-factory-service-manuals-literature-186552.html

 

if you are like me,

at some point you are going to get impatient waiting on an answer and then make a mistake.

 

did any of the bolts have metal filings on them?

if stripped, you may be able to use a slightly longer bolt.

there are likely more unused threads at the bottom of the hole.

 

the other solution is to use a helicoil kit.

 

the torque for these is very low.

do not over torque.

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The threads were clean, no sign of stripping at all. Some of the bolts had gunk and rust on the part that was not in the threads due to water pump gasket leakage. I'm tempted to just pickup a set of new bolts, but I cleaned them and ensured they would all bottom out in the holes with just hand tightening so they will probably be OK. I've seen these little bolts strip before (actually, the holes they go in, not the bolts), and I've done heli coil repair before, but that can be painful when there is not a lot of room to work. Not sure how close together the torque specs and the strip point are. Sometimes they are a bit closer than I would like, I have (not very) found memories of doing a brake job and stripping the caliper threads before it even got to the proper torque. Once bitten, thrice shy or something like that...
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Yeah it is very easy to over tighten smaller bolts. I usually tq the important parts and over the 15 years fixing vehicles for a living I can tell by feel when a bolt or nut is tight and probably a couple ft lbs or inch lbs of the actual spec. You just get used to this over the years.
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I broke down and bought an inch-pound torque wrench...one stripped hole is one too many....

 

I didn't see torque for thermostat housing, though I may have missed it. Short bolts into an aluminum/pot-metal housing. I'm guess 5 ft-lbs or so....

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You don't necessarily need a inch lb tq wrench. A foot pound tq wrench with a range from 5 ft lbs up will work just fine for most automotive applications. You just divide what ever the inch lbs by 12, so if you have 96 inch lbs it would be 8 ft lbs if divided by 12. I own a few tq wrenches for various applications.
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If you are concerned about the actual torque settings, then get an inch pound covering the range you need. There are a few less than $100. Crafstman has a wrench that goes from 25-250 INCH lbs. Don't get something that the 5 ft- lb range is at the lowest setting, it won't be accurate at that poundage.

 

O.

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Yeah they will. Like I said I have a few tq wrenches, foot lbs and inch pounds and the ft lb wrench is dead accurate at 5 lbs. If you take care of them and not leave them set at the last setting they will remain calibrated for a long time. Btw in reality how many nut or bolts on a average car actually have specs at or lower then 5 ft lbs? Not many and any one who knows how to work on cars should be able to tighten a nut or a bolt at 5 lbs without the need for a tq wrench.
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