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Discussion Starter #1
My friends car has a new crate 5.0 in it, and is stock except for a trick flow stage 1 camshaft and bolt-ons. The problem is, it has gone through 2 oil pumps already, and we are getting ready to put another one in it. THe motor has only 7,000 miles on it. What happens is the oil pump locks up and the shaft breaks. What could be causing this? faulty oil pumps? they are not high volume, just stock replacement pumps from Kragen. please help!

thanks
 

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About the only thing that will lock a pump up is dirt or debris in the pump, or if he has installed the wrong length drive shaft and the pump is binding.
 

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You need to take the pump apart and find out what is in them making them lock up. A friend had a valve seal break on his and the little metal ring was lodged into the pump.....
 

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before full assy.check pickup height by putting clay in the oil pan it should be no more than 1/2" pump may be running dry at times. just guessing at things to look at.have you been just changing shafts. with the same pump or has pump been changed again.it wouldn't be the first new part thats bad.i don't like hardend hd shafts personally.but have you tried one of them.
 

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Discussion Starter #5
its been a new pump each time, and the first time it had a hardened shaft, second time was a new stock shaft. the oil pan and pick up are both stock too....

thanks!
 

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I would look into the distributor shaft. Since a couple of pumps and shafts were used, maybe the dist is at fault. The dist could be sitting too deep on the intake if it is not machined to proper specs. Something could be wrong with the main cap alignment or deck height, but that is pretty far feched.

How long did it take for the first pump to go bad?, did it take a while for the second one to fail, or right away??

Anyway you shake it down, something is pretty wrong there.
 

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each time did you take the pump apart, what did you find. I once had a piece of valve seal get in there and it did the same thing. the only thing that is going to snap a hardened shaft is some debris. also check to see that the shaft is not to long, this would force the gerator in the pump to cut into the plate on the bottom of the pump. and could possibly cause it to lock.
 

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Hmm he's started to sound like me, three shafts in the last two years over here.

First shaft is still a mystery we tore pump apart and inspected everything couldn't not find a speck of anything, pump was seated properly on block and shaft was proper length :confused:

Second was from pump not being installed correctly (American craftsmanship at it's finest...product GES in Bedford, MA avoid at all costs), I have a main support girdle on and rather than make adjustments to get pump to fit knucklehead used longer bolts and tried to torque it flat. Never succeeded causing shaft to snap.

Third one a rocker arm broke sending all the bearings down into the motor, I could only fish out 1/2 of them but figured I'll gamble and keep running car since it's been like 2 degrees lately and just had motor put back together a month prior. I also figured bearings weren't going to get through screen because they're larger than the opening well aparantly one of the bearings made it's way down the discharge of the pump causing it to lock up.

So might want to check all of these things.
 

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What viscosity oil are you using? Not 20W-50 I hope. A new shortblock and thick oil can cause excessive oil pressure and may tend to overload the shaft. Other than that it has to be debris entering the pump chamber.

Oh yeah, Joe Dirte, large items can and do get past the pickup screen. When you start up a cold engine the oil is sometimes so thick it causes the screen to lift up exposing the suction relief hole. That relief hole is about 3/8" diameter.
 

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I just broke a hardened shaft when my pump locked up. The shaft same length as stock with stock intake and no trash in the pan other then the bearings that took a s**t due to lack of oil. pump was clean but the gears were siezed I couldnt even drive them out. The bottom of the gears were all chewed up as was the retaining plate on one side. 23,000 miles on the motor, regular oil changes every 2500 to 3000 miles. Wife was driving when it happened, didnt shut it down until it squeeled and died. Now I have a crank thats shot, four rods that are a nice shade of blue in the big end and four scored pistons. I tore the heads apart thinkin valve stem seals but they were all in tacked. No idea what caused it other then a faulty pump.
 

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In the past year there were two Corral members having problems with Melling oil pumps. In both cases the pumps would lock up after a short period of use. The bottom covers were scored with a pattern that looked like only half of the ring and rotor were contacting the cover. That would suggest that either the mounting flange for the cover was machined slanted or the internal race for the rotor/ring was sideways, ie the pump was machined wrong.
 

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Mine was a melling. I called Summit, who I purchased the pump thru and they gave me the # to a guy at Melling. I talked to Melling and was told to send the pump in. they would look it over and they might help with some of the damages if they determine it was a manufaturers defect. Odds probably are no matter what they will find no fault of their own. Maybe not. If Mellings are having problems then which pump do you all recomend?
 

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The bottom covers were scored with a pattern that looked like only half of the ring and rotor were contacting the cover.
Sounds awefully familiar, exact same thing I found!

me the # to a guy at Melling
Any chance this was Dan Bass? I talked to him myself, sent my oil pump in and never saw a dime.
 

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Yep Dan Bass it is. I sent it in a week ago no word yet. I figured I wouldnt see any money but I thought I deffinatly would get any if I didnt try. So it is begining to sound like melling are s**t no? Any suggestions for a new pump?
 

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GT40Capri said:
In the past year there were two Corral members having problems with Melling oil pumps. In both cases the pumps would lock up after a short period of use. The bottom covers were scored with a pattern that looked like only half of the ring and rotor were contacting the cover. That would suggest that either the mounting flange for the cover was machined slanted or the internal race for the rotor/ring was sideways, ie the pump was machined wrong.
Make that 3. Same thing happened to me. Autozone paid me to re-build my engine.
 

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Just subscribing.
I'm about two days from a Melling install myself, now I'm going to hold off. Anxious to hear the suggestions.
 

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Some gear sets were placed in pumps that did not allow proper clearance in the pump. SO when everything warmed up there was no thrust clearance in the pump and the gears would bind against the base plate. Build heat, and dissintegrate. Should be .003 to .005 clearance allowed between the base plate and the gear set when thrust up into the pump body.

Might want to contact Melling direct to get thier quality control for thrust clearance, and check the pump before assembling the engine.

No thrust clearance to a ARP pump drive shaft and a distributor such as an MSD can also lead to gear binding as the pump drive shaft forces the gear into the base plate. (It also forces the thrust bearing in the distributor against the casing and destroys it eventually.) Just because you can tighten the clamp doesnt mean its assembled correctly....
 
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