1938 Chrysler Imperial floating power motor mount R&R

[Daniel Jones]

I removed and replaced the "floating power" motor mount on my 1938 Chrysler Imperial recently.  With a few design changes, it could have been an easy task but the generator is in the way on one side and the combination mechanical fuel and vacuum pump (for the windshield wipers) is in the way on the other.  Engine bay splash shields all around further limit access and the bottom motor mount studs are not accessible with the shroud in place.  As it is, it took the better part of the day and my left arm is cut and bruised so par for the course.

 

I first removed the two nuts and split type lock washers from the top studs.  A ratcheting box end wrench worked well here as there isn't much room to swing the wrench.  I then jacked the engine up so the backing plate cleared the top studs and removed the top plate which was no longer bonded to the rubber isolator pad.  The bottom plate was not bonded either so the mount came out in two pieces.  Dry-rotted and compressed, it was well and truly perished.  To jack the engine up, I used a long floor jack with a wide board on the saddle and a piece of rubber anti-fatigue mat in between the board and the oil pan to prevent damage to the pan.

 

On the right side, I could barely see the frame hole, much less get a hand near it.  On the left side, the hole is hidden under the generator but I was able to get an offset box end wrench on the bolt head.  I mistakenly thought the bolts threaded into rectangular bosses underneath the frame and spent several minutes trying to unthread the bolt before I realized it was just spinning an 11/16" nut on the bottom.  BTW, the nuts underneath the car are accessed through holes in the lower control arms.  A long wobble extension and ratchet works from below but, in order to break the nut free, I needed a way to get a wrench to stay on the bolt head up top to keep it from spinning.  I used a neodymium bar magnet placed across the 5/8" end of a long offset box wrench.  Though small, the magnet is strong enough to hold the wrench in place.  Once loose, there isn't enough room on the right hand side to pull the bolt out with the box wrench in place so I levered the wrench and magnet off and grabbed the bolt with a telescoping magnetic pick up tool.

 

With the bolts out and the engine jacked up, the shroud was free to move forward (limited by the proximity of the radiator, the harmonic balancer and crank pulley) but I had to remove the mechanical cooling fan, upper pulley and fan belt to have room to rotate the shroud to the left side to get access to the nuts on the bottom studs.  Removing the belt requires the upper generator bracket be loosened but I removed it for paint, along with the fan and pulley.

 

Putting the shroud frame bolts back in proved trickier than getting them out.  The clearance is such that, while I could get the bolt to the hole, it needed to be rotated well past vertical to align with the hole.  I used a flexible spring-loaded 2 claw grabber tool.  That placed the bolt at the hole with the correct angle, then I used a long slender screwdriver to pry the bolt into the hole.  Before attempting that, I aligned the shroud and frame holes using a tapered rod.  From below, it was a dexterity test as I had to force my hand into the access hole while holding a large flat washer, split lock washer and nut.  Working against gravity, the washers need to be held in place while simultaneously threading the nut on.  The magnet could have helped with that but I didn't think of that until after I was finished and putting away the tools.  Once started, it was easy enough to wedge the bolt to the side to keep it from turning but I still had to put the box end wrench back in place up top to torque the nut tight.

 

As expected, the top studs needed to be shortened to have a chance of sliding the new rubber mount into place.  I used a small brass hammer to tap it into place over the timing cover and used nyloc nuts up top, instead of lock washers and nuts.

 

Though the fan belt sawed through the rubber mount, the belt wasn't in that bad of shape.  There's a bit of wear on the leading edge but that's it.  Still, I ordered a new belt and will keep the old belt in the trunk as a spare.  I measured the original non-cogged V-belt at a bit less than 51" around the outside and 11/16" wide.  It's marked with "Gates 650T Truck and Bus Belt".  Searching on that part number didn't get any hits but RockAuto lists a similar Gates Green Stripe Truck and Bus V-belt for a 1938 Imperial under part number TR24500 which measures 50 5/8" by 21/32" and a V angle of 36 degrees.  The product description says:

 

 Gates Green Stripe Truck and Bus Series V-Belts are specifically designed for heavy-duty truck, bus and off-road equipment applications.  
 Absorbs normal shock loads without damage to the belt.
 Molded notches reduce bending stress, especially on small diameter pulleys, while dissipating heat
 High modulus, high strength tensile cord
 Oil and heat-resistant construction throughout
 Meets SAE J636b and SAE J637 specifications
 Meets RMA oil and heat resistant standards and static conductivity requirements
 Notched, TA Cross Sectional Design
 EPDM Rubber Belt Material
 Polyester Cord Material
 Lifetime Warranty

 

They also list an AC Delco T24500 but it's not in stock and NAPA carries a Gold Stripe NBH 2524500 Truck and Bus belt which is likely made by Gates.  The belt took a few days to arrive so I took the opportunity to repaint the pulley, bracket and cooling fan.  I stripped the pulley and generator bracket to bare metal but only scuffed the fan before repainting.  I first tried brushing on some leftover black Rustloeum paint but it had thickened and didn't flow well so I sanded it off and made a hardware store run for the same paint in an aerosol can.  That worked much better.  I also stripped a couple more of the pulleys and found another fan that will get primed and painted with Imron for the 324 build though I think that engine may have come with a 5 blade fan.

 

I let the paint dry for a week or so before reassembling.  Space from the water pump flange to the radiator is tight and you need to install the upper pulley and fan over the studs while trying to not nick the radiator or scratch the paint.  The fan didn't want to slide onto the hub, presumably due to the extra thickness of the new paint.  Also, near each stud hole, there's a small dome that limits the wrench throw so I used a ratcheting box wrench to pull a pair of the nuts down evenly, then threaded the third by hand.  The final nut refused to thread on.  When I removed the fan, one of the nuts was missing.  I assumed it had just loosened and fell off but now I think the threads are bad and it was never installed.  I dropped and lost a couple of nuts trying to get one started without success.  I found a nylock nut that had more of a chamfer on the back side that I was able to get started.  It threaded on with difficulty but not all the way.  Once it was flush with the stud end, it didn't seem to thread on any farther so it might have started turning the stud farther into the water pump flange.  I stopped there and made a note to myself to run a die over the threads next time I'm there which may be sooner than later as the radiator shows some signs of leakage at the very bottom.

 

Getting the new fan belt on was also tricky.  With the painted generator bracket loosely bolted in place, the 51" belt is too short to clear the pulley.  Removing the bracket bolt and rotating the generator until it contacts the block provides just enough room to force the belt onto the pulley but it took several tries.  Another one of those things where a third had would have come in handy.  Once the belt was on, there wasn't room for a ratchet with a deep socket but I have an offset box wrench that has the same angle as the bracket that I used to do the final tightening.  I used anti-seize on all the threads so I had to clean up the mess to finish the job.

 

A few days later I drove the Imperial to work and the shuddering when the clutch is engaged is gone and the car seems smoother to drive, though it was already pretty smooth.  Given the condition of the motor mount, I thought it might also need transmission mounts but those look good.  I thought aboout ordering spares just-in-case but the vendor (Andy Bernbaum) I got the motor mount from didn't have a listing for them.  Also, I topped off the radiator with coolant because it's seeping out at the bottom.  I need to check the 1937 radiator but I don't think it is the same as they changed the hood design.  

 

 

[Daniel Jones]

Not sure why the mount pictures are upside down but this is the way it's installed in the car