Vacuum pump breaking mounting bolt
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From: Perry Georgia
Vacuum pump breaking mounting bolt
I have a 1987 F250 with a 6.9 N/A Diesel. I've never seen this discussed but in the last 2 years I've had 2 of the mounting bolts break off inside the housing that the pump bolts to. Both times it's the bolt that is what I'd call the stationary bolt. The other bolt is the adjusting bolt. Has anybody else had this problem and if so what can be done to stop this from happening again. Everything lines up as far as I can tell. The adjusting bolt stays and keeps the pump from falling off just doesn't keep tension on the belt and both times I've lost the brakes which is a real thrill
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Joined: Feb 2003
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From: Muskegon, MI (home)
I personally have never had this problem. I guess the first place I would start, would be checking pulley alignment. How much tension are you putting on the belt? It seems too tight could put undue stress on the bolts. Hope this helps, good luck.
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From: Perry Georgia
Pulleys all line up as far as I can tell. Nothing has been added or changed in a number of years other than changing the alternator with another alternator same type and that was a couple years before the first bolt broke. Been thinking of using a grade 8 bolt.
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From: Perry Georgia
I've been using the standard bolt you can buy at the local hardware store, not a grade 8 bolt. I"m just watching it closer than before
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Logistics Pro
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From: Western Mass
Standard hardware store bolts are grade 2. Good for building random crap in your garage, but cheap and weak. Most of the engine hardware would be grade 5 or grade 8 if its an SAE bolt. However, it could also be a metric bolt which would most likely be class 9.8 or 10.9 (which are similar to grade 5 or grade 8) Note that both standard (SAE) and metric bolts are used on the engine, depending on if its a regular Navistar International attachment point, or a bracket that Ford made to bolt on accessories.
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From: Perry Georgia
Yes, it is a metric bolt I've been using. I know the first time I replaced the bolts, both of them I had a hard time finding them but after I figured out they are metric, no more problem. Still holding together!!
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From: W. of Seattle, Kitsap P.
CHEAP BOLTS! Where are they breaking? I suspect in the thread! A surface manufacturing defect (or by other cause) in a bolt such as a pit or notch or even a deep scratch in metal is a potential failure point under fatigue stresses. It's like - if you file a very tiny mark or just use a knife to make a tiny cut mark in a coat hanger wire and then bend it back and forth it will break where that mark is. In physical metallurgy this property is called 'notch toughness' which affects the fatigue strength. Cheap hardware store bolts are not meant for use in engine applications where fatigue stresses are present and fatigue strength is important.
I just looked at the small bolts holding my vacuum pump bracket and I can't quite read the entire embossed number on the end but I can see the .8 so it must be the 9.8 rated bolt that tecgod13 mentioned
I just looked at the small bolts holding my vacuum pump bracket and I can't quite read the entire embossed number on the end but I can see the .8 so it must be the 9.8 rated bolt that tecgod13 mentioned
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