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99 sls ,How hard is it to replace front hydr. mount by radiator? I dont see any torque struts on this any where..ant find aftermarket hydro. mount any where must have to go to the dealer.:confused:
 

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Pretty good job to replace some do not have torque struts. Rockauto.com shows a mount #2838 @40.99 for 99 model check their site picture to be sure . sts96 PS do not lift the engine by the pan it WILL crack!!!!!!.
 

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With the right tools, the front engine mount should take about 2 hours to replace. You can order a new mount from GM part direct or Rock Auto and it will be cheaper than getting it form the dealer. The easiest way to change the front mount is to either put the car up on a lift, or use some tall, stable jack stands. If your using jack stands, you'll need to get the front of the car at least 2-3 feet in the air, so that you have enough room to work. Once you have the front of the car off the ground, position a jack (or T-stand if using a lift) on the metal bracket covering the exhaust pipe leading from the front of the car to the back. It can take the weight of the engine safely without damage. Next, position another jack along the front beam of the engine cradle, where next to where the engine mount bolt is located (in the middle of the beam). Once you have both of these jacks in place, remove the front two bolts, and the two bolts in the rear of the cradle that are closer to the car (there are four in the back, rmeove the two closest to the front). I would suggest using an air-gun as these bolts are torqued to 140ft/bl's form the factory. Once you have those bolts removed, remove the nut holding the engine mount to the cradle. Then, lower the jack holding the front of the cradle up, until you have enough room to work (about 4 or 5 inches). Be careful not to pull too hard, as the ABS motor, and brake lines run along that frnt part of the cradle. As long as you pull gently, they will just flex with no issues. Now for the difficult part. Attached to the engine mount, is a braket, held onto the block in four places. Two bolts at the top attaching it to the exhaust manifold, and two nuts at the bottom securing it to the block. You will need at least 2 12" extensions and a universal joint to remove the upper bolts. The lower ones are much easier. Also, the bottom right one has a metal bracket that must be removed before you can pull the braket out. It simply slips off of the bolt. Once you have all four bolts removed, you can rotate the braket sideways (I recommend clockwise) until it and the engine mount are resting on the cradle. If you can't pull it out, just nudge the cradle down a little farther to make enough room for the braket and mount. Once you have removed the braket and engine mount, you need to removed the final nut, holding the top of the engine mount onto the bracket. After you have bolted the new engine moutn to the bracket, simply reverse the process. Slip the new mount and bracket up into the engine compartment around the cradle the same way you removed it (i.e. sideway, makes it easier). Than rotat it back around until it is sitting up right. Next, slip that metal bracket back onto the lower right hand side of the bracket, and then reinstall all four bolts. After the upper and lower bracket bolts are installed, used the jack in the front to move the cradle back up into postion, so that you can install the lower engine mount nut. Once that nut is installed, reinstall the four bolts that were removed from the cradle (two in front, two in back). I would highly suggest using a torque wrench to install these bolts. They should be retorqued to 140lb/ft. On a side note, the engine mount nuts should be torque to around 30-40lb/ft. I would also suggest buying some Threadlock just to make sure they don't back out once you install them. I knwo this seems like a hell of alot to do, but if you have the tools, and the space needed, it's actually not that back. It's alot easier that pulling the radiator out of the front fo the car, like they would at the dealer. As I said before, with the right stuff, it should take more than 1-2 hours. Using jackstands thoguh, it might take 2-3 as there isn't as much space to work with. Hope this helps.
 

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Thats funny I work at a dealer and we don't pull the radiator---We also don't pull the two rear cradle bolts either for that matter---(good way to get hurt if whole assembly falls out) I would not recommend it unless you have at least moderate mechanical skills. Just my 2 cents----Supercrew632
 

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Well, when I did it, I was at the open shop at my Tech school, and had my car up on a drive on lift, and had a full box of every snap-on tool you could think of next to me. At the time, looking in my service manual, that was the easiest way to get the job done with the time I had. I also use three seperate T-stand to support everything, so that there was no danger of it falling, not to mention that I still left the the last two bolts in that very back of the cradle to support it while I dropper the front. Just otu of curiosity, how do you remove it at the shop you work at? Other than dropping the fornt of the cradly, pull the the radiator is the only onther way I could see to access it. I'm just curios as I'm going to need a way to find some room so I can change my A/C clutch assembly soon, as well as my harmonic balancer and accessory belt.

edit: I misread your response. I didn't pull the radiator (what the FSM says to do) and I did leave the last two cradle bolts in the rear in, so I could just drop the front.
 

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The front 2 bolts are the only ones needed to be removed. It is done on a hoist--wtih a pole jack supporting cradle so it can be lowered slowly. You can do this same thing for air conditioner compressor sevice to make room. The balancer, you use a pole jack and remove the three bolts on the right side and slowly let it down to access the balancer and get a puller on it. I hope I helped---if I left anything out please feel free to ask----Thanks---SUPERCREW632
 

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Discussion Starter #7
99 sls

Well replace fr rt hydro mount and rear solid trans mount,some of the thump is gone but still thumps? ONLY at slow speeds stop and go traffic drive me nuts..IF you press the gas like and older 70s person its fine.
when you jump on the gas it will thump,IS there another hydro mount for the trans i dont see ? To make sound easy its like driving a manual trans in 1rnd gear and driving at10mph you step on the gas and it to much gear so its bumps
when hit gas.
hopes this helps with question..
 

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Discussion Starter #8
Well replaced front rt mount and rt trans mount and rear trans mount still have thumping. So out car back in the air power braked it and you can see the cradle jumping in the front right of car thumping as you hit thr gas...
So im going to replace the cradle bushings next..Or would the strut mounts cause this???? 99sls 89000 miles love the car besides this.. New mich hydro edge rides exxx.
 

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Danbuc & Supercrew. Great explanations. How about posting those in the tech tips section for future reference?
 

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apollo said:
99 sls

Well replace fr rt hydro mount and rear solid trans mount,some of the thump is gone but still thumps? ONLY at slow speeds stop and go traffic drive me nuts..IF you press the gas like and older 70s person its fine.
when you jump on the gas it will thump,IS there another hydro mount for the trans i dont see ? To make sound easy its like driving a manual trans in 1rnd gear and driving at10mph you step on the gas and it to much gear so its bumps
when hit gas.
hopes this helps with question..
Just to let you know Apollo, you're not alone with the thump. To me, it feels like excessive lash in the final drive. If anyone has the answer, give it up.
 

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El Dobro said:
Just to let you know Apollo, you're not alone with the thump. To me, it feels like excessive lash in the final drive. If anyone has the answer, give it up.
I concur---alot of complaints at my dealership about this concern----I personally have called GM technical assistance on a few----they claim after the trans has alot of miles---65,000 or more there is a little wear/excessive lash. Trans can be rebuilt for peace of mind, but not necessary at this point as nothing is going wrong internally--just worn/broken-in gears. I believe it is in the final drive or chain assembly--The front engine mount tends to help alot (if it truly is broken) but not always the fix. If it was my car, I would just drive it. Hope I helped out on your question.......

Supercrew632
 

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I've got that as well. I guess if someone really wanted to mess with it, they could pull the trans out and mess with the bearing preload on the diff, and screw around with the backlash on the gears and chain until they got rid of all the play. I think people just notice it more being not only a FWD car, but a powerful one at that. I've driven many RWD cars that exhibit the same symptom from the rear end. You just don't notice it as much, because your much further away from the source. Just as an observation, I notice it most it my car when I coast down a hill. While doing so, you take all of the strain of the gears an allow them to move a little. While still going downhill, if you step on the gas, all the slack gets taken back out of the gears as power is re-applied to them. This is felt as the thump from the trans.
 

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Discussion Starter #13
Well thank you for the feedback...Its just that you can see the cradle jump also when lifted in the air and power braking it. just on the right side you can also pull and push on the cradle and make it move..
 

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Hmm....Have you checked to make sure that all six cradle bolts are tight? A bad motor mount shouldn't cause the cradle to jump like that when power breaking, since the engine it rocking on the rear tranny mount. Check to make sure they are all tight. The torque spec on them is about 140lb/ft.
 

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I agree with DANBUC-----This should not be happening----it is possible the cradle bolt mount has broken loose out of body. only fix is to have a good welder repair it. I would go to a dealer, pay the hour diag so you know for sure, and let them tell you what it is and what it would take to fix. I would not drive that car if that is occuring--safety issue---
SUPERCREW632
 
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