[DeTomaso] Busted motor mount bolt

John Maffeo johnmaffeo1 at yahoo.com
Mon Mar 5 23:17:06 EST 2007


Are the rubber washers unique to our cars? I should probably replace mine....
   
  thanx,
   
  John

JDeRyke at aol.com wrote:
  First, WHICH motor mount? The right side assembly easily unbolts and removes 
as an assembly once weight is taken off the powertrain with a floor jack & 2x6 
across the pan. But the left side mount must be unbolted from the car and 
engine, then split in two by unfastening the long connecting bolt between the 
halves, while the assembly is still captured between the frame, engine and 
gearshift support. This allows you to separate the halves and work them around the 
gearshift support. Unless things are rusty, this is really not that difficult. 
Once out, you can try grinding a slot in the end of the bolt in the block & 
using an impact driver (most have 1/2" drives so ratchet-wrench extensions fit 
perfectly). 

But in most cases you cannot get a clear shot at the broken bolt with a 
driver, so my preferred method is to get a good cutting torch, heat up the visible 
end of the broken bolt, and once its red-hot, hit the oxygen lever! The 
remains of the bolt will come out as a fountain of molten steel, so wear a welding 
hood & arm protection! There seems to be a sort of insulation-barrier between a 
bolt and the part its broken off inside, so the block threads will be 
completely unharmed. I've even done this to broken studs in cast-iron exhaust 
manifolds. Run a tap thru the hole to clean it out and use std gr-5 replacement 
bolts. 

The reason most Pantera engine mount bolts (on the block side) break is, the 
rubber insulator between the motor-mount halves compresses from age & engine 
weight, and the inside edge squeezes down more than the outside edge. This puts 
a side-force on the bolts, bending them. Bolts don't like being bent and will 
soon snap. You can overwhelm the problem by replacing them with gr-8 bolts, 
or the next size larger gr-5 bolts (after drilling & tapping), but the true fix 
is to either change the rubber washers every decade or so, or at least loosen 
up things and rotate the old rubber 180 degrees so the collapse evens out 
side-to-side. 

And do NOT use polyurethane washers as a replacement here! Poly is wonderful 
stuff but in this position, it will MELT from exhaust heat and you will have a 
memorable time getting the left mount out of the car. It took us several 
hours with chisels, hammers, a hacksaw and huge pry-bars to change a brand-new 
poly washer at the track one year, after a single 10-lap event. Good luck- J 
DeRyke


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