05 STS V8 AWD engine mount replacement

It's your engine, transmission, driveline
Post Reply
Posts: 13936
Joined: Wed Oct 23, 2013 10:28 pm

05 STS V8 AWD engine mount replacement

Post by kevm14 » Mon Feb 24, 2020 9:11 am

Going to collect tips/tricks/experiences for this job.

According to this guy, removal of the driver's side manifold/cat assembly was required:
https://www.cadillacforums.com/threads/ ... wd.800849/

I believe that is the cat that is giving me the P0430.
Finally got around to replacing the engine mounts. I wasn't able to find much info on replacement of mounts for an AWD, Few threads on what I suspect are for RWD. So here is a few things I ran across for anyone needing info on how to replace mounts in their AWD.

I was able to do this in my driveway on jack stands. A lift would have help. I was hoping to get both sides done without removing the exhaust manifolds. However, the driver side manifold and steering shaft had to come out. The manifold heat shield was almost impossible to get out. So there was collateral damage. Once manifold came out I just lowered the car down on a jack stand placed under there oil pan and out the mount came. (also loosen the fan shroud) The Revshift mounts basically drop right in with no issue. (no way I'm putting the OEM mounts back in to go bad and do this all over again) I also had to drill out the old bolts from the cat. I'm sure a good torch would have saved me time and a few bits. I only had a propane deal that didn't seem to get hot enough.

The passenger side I was able to leave the manifold in however the axle needed to come out to allow the car to drop down so the mount could clear the top bracket. Clearance was still tight and had to basically yank the mount out with a rope hooked around the top stud.

The whole process is time consuming due to the lack of space. Not sure of the total time spent working on it as I had to stop several times to do other stuff and a day of rain. I'm guessing 10-12hrs total. I'm sure 2-3hrs was just me thinking about how to go about it without making more work for myself.

My local shop quoted me $1700.00 of labor to install the Revshift mounts. The mounts cost me 140.00 plus 40.00 in extra parts. (nuts, bolts and flange gasket.) So for me it was worth the effort as I had all the necessary tools to do the job. It's border line just paying the money but I actually like turning wrenches. As you can see this was straight shady tree. The goal was to fix it without breaking anything so my methods may not be ideal. If anyone was contemplating do this repair on a AWD I hope this provides some sort of idea what may be involved.

Next, valve cover gaskets.
Actually removing a manifold isn't hard on the avg. car. However, on this STS the working area is very tight on the driver side. I was able to get the first 4 bolts from the top and then the last 4 bolts towards the back of the motor from the bottom with long extension and swivel. You'll spend alot of the time working blindly. Feeling for the bolts etc. (skinny fingers and hands are a plus) Another issue with my removal of the manifold was that I backed out both studs which made getting the manifold out a easy. However, you need these studs in place to hold the gasket in place while putting the manifold back in. I screwed them both back in and hung the gasket, but wasn't able to get the manifold back in due to the front stud catching the inside of the manifold. took that stud out which made the gasket drop but at least I had the rear stud to hold the back end up. Once I hand the manifold back in place you just need to from the top of the car fish the gasket back into place and place the first bolt in to line everything up. Basically torque all the bolts back up. I could have use my air ratchet but didn't want to round any of the heads so a normal ratchet I used.
I didn't see removal of steering rack. It sounds terrible but if I really do end up needing to remove driver's side cat/manifold, why wouldn't I just replace the damn thing?

I think it is a good plan to have the Roadmaster back on the road and drive that and/or the V for a while until this job is done. Realistically it may be in the garage for two weekends, unless I take a little time off work. Which I may want to do anyway due to lull in holidays between Feb and end of May.

Posts: 2556
Joined: Thu Oct 31, 2013 2:20 pm

Re: 05 STS V8 AWD engine mount replacement

Post by bill25 » Tue Feb 25, 2020 4:30 am

It sounds terrible but if I really do end up needing to remove driver's side cat/manifold, why wouldn't I just replace the damn thing?
I agree.

Posts: 13936
Joined: Wed Oct 23, 2013 10:28 pm

Re: 05 STS V8 AWD engine mount replacement

Post by kevm14 » Tue Feb 25, 2020 9:04 am

The only hangup I have is I'd rather put that money toward a Northstar Performance tune, which is like $475 (and not yet available).

Also, the offerings for CA-emissions cats have gotten even worse. The only one I still see in Rockauto is Dorman, and it is not cheap:
DORMAN 673931 {#12567687} C.A.R.B. Compliant; Manifold Converter Info
Left; w/LEV Emissions Level 1

DORMAN 673930 {#12638982} C.A.R.B. Compliant; Manifold Converter Info
Right; w/LEV Emissions Level 1
I guess I need the left which is....the exact cost of the tune. So now I'd be banking on tune availability before May 2021 (unless I can still squeak a pass during the times where the light is off, like it is right now). If I just park the car as soon as possible after the light goes off, and the next time I drive it is to Tire Pros, I could probably get it to pass still. It's dangerous because they tend to shut it off and restart once or twice as it goes between the bays. And they don't do emissions until safety is good. So I run the risk of the light popping on after they start it to move it out of the safety inspection bay. Ugh. Worked out last time though.

I could also run a federal cat which is only $275 but I would definitely have to reprogram. Not sure what the point would be then. Unless the federal cat is less restrictive (tiny performance boost?). But my cat is fine and unless it physically fails, it doesn't HAVE to be replaced.

I still want to see if I could flash my ECM to a federal calibration somehow. I don't know if it is locked to VIN and since GM knows this is a CA emission car, it wouldn't let me flash anything else. Not sure how any of that works. The theory with that is A) If my CA cat is marginal, it could still pass the more relaxed federal diagnostics or B) Would allow me to run a federal emissions cat in the event that it still needs to be replaced (every other option exhausted, no pun). I also wonder if there would be extra performance in a federal ECM calibration but that may be wishful thinking. Then again, if GM could make an optimized STS (with all the power and fuel economy that they were targeting) AND meet CA emissions, why wouldn't they just build them all that way? To spite CA (I can't blame them)?

Posts: 13936
Joined: Wed Oct 23, 2013 10:28 pm

Re: 05 STS V8 AWD engine mount replacement

Post by kevm14 » Fri Mar 06, 2020 8:54 am

https://www.cadillacforums.com/threads/ ... s.1095168/

This is promising. There is really very little DIY accounts of STS V8 AWD engine mount replacement. I correspond with this guy fairly often (he's the top contributor and I am the 2nd, which is a little sad - the group is small) and he just did his mounts. I'll copy his post:
They are a special kind of nightmare.
That said, removing anything extra on the AWD 4.6 is not necessary.
Was on a lift, I would have lost my mind doing it on the ground.
Used a screw jack and block to lift the engine, very slowly.
On the left (driver) side I used a pry bar to bend the exhaust manifold heat shield up ever so slightly just where the upper mount nut is, was able to get a 21mm ratcheting wrench in and slowly got the nut off. I used an even longer pry bar to pry the mount out between the cat and steering gear, it was not easy whatsoever at first until I switched to the longer pry bar, then it was just medium difficulty.
Finishing the right side on Sunday.
OK there's a lot there. And he did only one side though the passenger side should be "easier." I followed up with this litany of questions:
Well I'll bite. Looking for info on several interference areas:
You did not touch the steering rack?
You did not touch the fan or fan shroud when moving the engine around?
You didn't loosen the subframe bolts?
You did not touch the alternator for pass side mount?
Didn't have to remove any manifolds?
Didn't have to remove manifold heat shields?
This seems like all good news if all are affirmative...though I don't have a lift. Was considering a Quickjack which would get the car like 24" into the air. I could probably find a lift to do the job but it adds another level of inconvenience because it is like an hour away.

All that said, I was planning to combine with front LCAs so I was going to lift the rack anyway. Would that have helped?

Sorry for the barrage but there is precious little DIY info on STS V8 AWD mounts.
I'm realizing that he won't be able to answer my question about the alternator yet.

He'll get back to me. It does sound like I need to think again about doing this on the garage floor (at least on jack stands), especially if the recent brake line work on the Roadmaster is any indication. If this pushes me over the edge to get the Quickjack because I can get the car really high easily, then I am all for dropping some bucks on that because it may pay dividends as a DIY (I am not going to stop working on cars any time soon). I think if I rig it so the Quickjack is like a low version of what you can do on a lift I will be best off. If I can sit up straight under the car for example (not sure what that height requirement would be), that could be huge. If I can get a mini screw jack like the kind you'd use to support a transmission or something, that would also be a big help.

I think this is worth planning for and investing some money.

Posts: 13936
Joined: Wed Oct 23, 2013 10:28 pm

Re: 05 STS V8 AWD engine mount replacement

Post by kevm14 » Fri Mar 06, 2020 9:44 am

He replied again.
Haven't done the right side yet, saving that for Sunday since the left side took so long.
I did unbolt the fan shroud, I'm not sure if it even made a difference but I also didn't want to lower back down just for that. I think if you knock it out in the midst of doing your lower control arms it may be easier since the steering rack will be totally loose and may provide some more room.
I didn't remove anything else.
The two biggest hurdles I ran into were
1. Squeezing that S.O.B. out with the long pry bar, once I switch up my method to the much larger pry bar it was way easier.
2. I'm using the creative steel mounts (good luck to anyone who decides to go with the OEM ones as I have no idea how you would get them in without removing the exhaust manifolds) and ended up having to drill an extra hole in the frame on the driver side where the stud on the mount lines up. I can only assume the bracket or frame is slightly different on the AWD as other guys with the RWD/V have not complained about this problem.
Basically the studs on the replacement mounts are at an about 30 degree offset between the top and bottom, well, on the factory mount the offset is at about 90 degrees. So I drilled a hole in the correct place through the frame, using an air drill and a long drill bit to reach in far enough as I used the already existing hole in the bottom the frame where the lower mount nut goes.
The misaligned studs was easily the most frustrating part of the whole thing, but at least it was fixable.

Using a flex head 21mm ratcheting wrench would have made this job infinitely easier, but unfortunately the shop I used didn't have one, so I have one being delivered tomorrow.
The flex head wrench will be a necessity for me on the right side upper mount nut.

Flex head ratcheting wrenches for the win, they are the singular most useful tool purchase I have made along with the obvious socket sets.
So that's an issue. I have new OEM mounts. But it may be possible to talk me out of them (effectively wasting them but maybe they are compatible with the SRX) if it really makes the difference between removing the manifold, and not removing the manifold.

Other than additional cost, my only other holdup is NVH. I am tired of the vibes. I don't want to go to a hard urethane mount if I still have vibes. Chances are, they will be way smoother than the broken/leaking OEM mounts, but not as good as new OEM mounts. That may just be a compromise I need to make here for sanity purposes.

I did to Creative Steel mounts on my CTS-V and they do for sure transmit more vibes but I don't mind as much since it's like an LS6. The NorthStar is supposed to be silky smooth from idle to redline and that's how I want it ideally.

Posts: 13936
Joined: Wed Oct 23, 2013 10:28 pm

Re: 05 STS V8 AWD engine mount replacement

Post by kevm14 » Fri Mar 06, 2020 9:48 am

Or I could go to their webpage and actually see what they have.

https://creative-steel.com/shop/cadilla ... t-shields/

Look at that. They now offer 3 durometer options. Stage 1, 2 and 3.
05-11 STS STS-V ENGINE MOTOR MOUNTS (For 8 cylinder cars only)

Our urethane STS / STS-V Engine Mounts are a direct replacement for worn factory mounts. They will fit just like the factory mounts with no other modifications. The factory mounts are designed as a rubber bladder with liquid in them to create the soft, comfy feel of the Cadillac. After these mounts have had some miles on them, they crack and leak out the liquid creating a blown motor mount. You will notice if your engine mounts are bad by how your car turns off. If your vehicle rumbles to a stop like a diesel engine, your engine mounts are shot.

What sets our mounts apart from our competition is our engine mounts have a two-part interlocking steel framework encased in urethane to give engine support in both directions of push and pull. When the engine tries to twist under acceleration the driver’s side of the engine tries to lift, putting that mount in tension (pull apart) and the passenger side mount in compression (push together). Then, when you gear down into a corner or to stop, these forces are reversed. Our mounts are correctly designed and take both of these forces into account. BE AWARE that some polyurethane engine mounts sold on the market today only have bolts sticking out of each end with nothing to keep them from ripping out of the urethane when these forces are applied to the engine mounts.

We are now selling three different hardness’ of urethane for these mounts:

NEW SOFTER Stage 1: Stock replacement-Recommended when passenger comfort is the primary concern with little to no performance upgrades.
Stage 2: Performance mount-Recommend for spirited drivers with multiple performance upgrades. “Best seller”
Stage 3: Full Race -Recommended for dedicated race vehicles. These rigidly mount the engine to the vehicle and will transmit vibration.
I think Stage 1 is what I want, especially since these are also STS-V mounts (designed for way more power). I wish I didn't have to spend another $200 as I think I already have $200 into the new OEM mounts. But it may just be the right thing to do given the access issues in the engine bay. Not having to remove the manifold is huge I think.

These basically look identical to what I put in my CTS-V back in 2011.
CS STS mounts.PNG

Posts: 13936
Joined: Wed Oct 23, 2013 10:28 pm

Re: 05 STS V8 AWD engine mount replacement

Post by kevm14 » Fri Mar 06, 2020 10:25 am

I just sent this to CS, regarding the hole the guy had to drill. I think it was for one of the locating pins (he said "stud").
Good morning,

I have used a pair of CS mounts 9 years ago in my CTS-V and other than some vibrations, they have been performing well.

I now have a 2005 STS that is NorthStar and AWD. I am considering CS mounts, in the Stage 1. However, the STS has different part numbers for RWD and AWD. I am sure the RWD is the same as the STS-V. But do you know what is different about the AWD? It could be the clocking of the locating pin. Can you guys look into this? Let me know.
Maybe they can make me a set for AWD to be 100% compatible? That may be a bit optimistic but won't know unless I ask.

Post Reply