Okay bear with me here. Get back after being gone 6-months and drive the snot out of the Vette. Come to find the lower power steering pump bracket smacked up and grinding against the harmonic balancer. The rear bracket from driver's motor monut to rear of pump body is cracked off in 2 pieces. The lower bracket stud is no where to be found and later I find the stud broke off deep inside the block. My daily driver was stolen so I'm using her as a daily driver with one stud and the rear alignment bracket holding the damn pump in place. Last two days when letting off the gas after a good acceleration I get a horrible vibration like the block is coming out of the car. I cannot find which motor mount is bad, if it's bad at all. I jacked from below (oil pan) and the whole car wants to lift (carefully with oil pan) I see no break in the motor mount stud, I see no bolts missing or loose between scatter shield and eng/ tranny, I see no loose bolts on rear tranny mount and drive shaft is tight.

I know it's a motor mount. What else would cause the rear PS pump mount to break in two. I have to pull off all the accesories/ vibration balancer to get at that broken off stud but before I start that I need to find the culprit. Aside from removing the motor mounts and viewing them out of the car how can I check them?

 

Ok, Ok,

I'll fess up. I took your wife for a spin in your car while you were gone.

You might find a few more things busted.

J/K

sounds like the wife may have done some hot laps in it.

 

No was me doing too many 6000 RPM clucthc dumps when I got back.

Okay with all these "Geniuses" in the CFOM with their 600+ HP Vettes no one knows anything about motor mounts?

 

Here is how you check them. Open the hood. Set the parking brake. While someone watches the motor mount put it in 1st gear and take up the slack. Then accelerate a little and let the clutch out enough to strain the motor. If the mount is bad it will raise up and separate noticably.

 

Can I ask my mother-in-law to stand in front and watch for me. I'll take "out the slack" with another 6000RPM clutch dump.

Seriously thanks for the input.

David

 

i don't believe it. its not your personality.

someone who cleans the undercarriage of their car with q-tips doesn't do clutch dumps.

 

Not to mention that he keeps the tooth brush companies in business lol.

Forgot to add do the same thing in Reverse gear as well and watch the mounts.

Hey come on I had to add something of value here.

 

Sounds like a good way to check it. Except I would not rely on the parking brake. Chances are it's the drivers side. Might be part of the reason for the power steering bracket issue.

 

that bracket is a real pain in the *** to put together...i can't imagine why it would break how badly out of alignment are your belts....wait a minute did the harmonic balancer walk??? and when it walked it forced itself into the PS pump and pushed it forward breaking the mount?.....if you use a reverse drill in that broken stud i bet it will walk its way out, but i'm not sure how you can get at it

 

Bob what do you mean did the balancer walk?

 

What he means is sometimes the outside ring of the harmonic balancer will slide on the rubber that binds the outside ring and the inside mounting flange. This is why you might have seen a few posts that stated they could not time there car because the outer ring has moved.

 

Well if it walks and the polymer alows the inner core and outer corer to move separately from each other correct? Still has the same outer metal core meaning the same outside diameter thus how would a "walking" vibration dampner hit a PS pump bracket over a "non-walking" vibration dampner. It's not like if it walks it magically swells from 6" to 11" and hits everything in the way.

 

It's most likely the driver's side mount if it's the mount at all. Also check the driver's side lower a-arm mount. It could have broken loose and moved up to hit the ps pump. I would change both engine mounts anyway. It's a couple hour job.

 

I've worked on a 71 where the inner and outer parts of the dampner were seperated. The outer part just shoved itself against the timing cover. It wouldn't affect thie PS bracket. Is the belt alignment good between the ps pump and crank pulley?

 

Solid mounts are easier to see:



The PS brackets do tend to break at the slot due to the twisting action from the belt tightness. What you describe as the PS pulley hitting the frame is how I found that my motor mount was busted, and the test with using the parking brake (and blocking the tires) while starting to let out the clutch resulted in the engine lifting slightly. As you can see I replaced the mount with a 1/4" thick solid MOROSO mount. I didn't get any increase in vibrations, but then it's just an L48 that purrs like a kitten...if you have a lopey cam or rough idle then a solid mount might not be a good choice for a daily driver...I don't know.

 

You are very correct it would not effect the pulley unless it came off and went against it.

I was just saying what the other person meant is all. Sorry I did not go further into it.

 

Go with new poly mounts.

I had a problem with mine on the 69 and the fan was hitting the top of the shroud and cracked the blades. Did the test mentioned above and the drivers side was split. Put the poly mounts on with a new fan and no problems in 4 years. I'd also heard that solids added way too much vibration to the frame, especially with a high HP engine.

BTW, I thrash that car all of the time so I know they work!

 

Just put my engine back in and used poly mounts for both the engine and transmission. My vibration problems were particularly bad since I have a Hurst shifter (mounts directly to the transmission). Vibration up through the shifter handle was so bad that I had to take the ball off in order to reduce the noise from the rattling.

 

you are correct, i thought when you said it was hitting the PS pump that the balancer had seperated and come up behind the PS pump bracket and some how put pressure on the bracket, (my bracket is close to the balancer but is not in front of it. i wasn't sure if yours was similar or not).....as opposed to hitting the side of the balancer....you are correct the diameter of the balancer would stay the same unless it exploded some how....i guess we can rule out that theory, perhaps it wasn't the best theory, i guess i'll have to have a beer to recoup...

 

Bob and guys thanks for your inputs. Checked the motor mounts as described above. I don't see a problem but the vibration is still there. Becuase of the way the power steering came apart I'm convinced it's related to the mounts. Still tommorow I'll check all the half shafts and drive shaft for looseness.

I'm really perplexed by this as well as I should mention the fan appears to be to the right and down within the fan shroud, the belt/ hose protector which is bolted to the altenator arm was ripped off the altenator bracket and is no where to be found.

WTFO??!!