A/C vibrations and Motor mount insersts

[Elbow]

I have been driving my "new" to me 2006 GT for the past few months and enjoying it thoroughly. However I can't resist the modification bug and have started down the path to addressing some issues.

The first thing on my list was to reduce the slop in the engine mounts as this car seems particularely soft in that area. I went ahead and installed the Cork Sport rear mount inserts that had rave reviews. When I have the AC off the vibrations are barable, there is a rather noisy startup jolt and when at really low rpm's and driving you feel the engine a bit more. But overall the vibrations are minimal and within what people described. The engine does not slop around as it did before.

When the A/C is on though and I sit at idle the car shakes, alot. Now I realise that the A/C was going to cause some additional vibrations but this is ridiculus. It is more of a resonance possibly, like the vibrations are feeding off themselves to make it worse? My wife actually got in the car with the A/C on, started it up, felt the vibrations and imediately shut if off and left the car there as she thought something was seriously wrong with the car. It has only been a week and probably about 100km on the inserts, I know there supposed to soften a bit but I don't think it will be enough to reduce the A/C issue.

So has anyone else had something similar? I'm thinking about looseing off the bolts and re-torquing them to see if it changes anything? I don't know if there are other issues at play here but when the mount was out this was one of the smoothest cars, save for engine lash. I have contimplated taking out one of the two inserts to see if I can allow the soft rubber to dampen some of the vibrations while still having some stiffness for engine lash?

If I can't get this figured out I will be posting these for sale because it's a deal breaker for a daily driver. I appreciate any input :)

[stevenma188]

I also have the same thing with my AWR mount. The car feels fairly normal with the AC off, but with the AC on there is a lot of vibrations. This is a tradeoff of stiffening the motor mount. If you search here, some aftermarket mounts are more susceptible to vibrations than others.

[Donutz]

I hate to say it but CS inserts blow. I had them. Yes, they seem to vibe more harshly than full rear mounts, AC on or off. Retorquing the bolts will do nothing.

I installed mine and ran them for a few months. They do break in over time, but also lose a lot of their effectivenss. I swapped for a Medieval rmm, then went back to the inserts. They were harsh harsh harsh; just as harsh as day 1. I then went from the CS inserts to CPE.

If they are new they will settle in. If they are used, or already broken in they won't get any better.

Sorry dude.

[Elbow]

Thanks guys for the input.

Jason are you saying that a full rear motor mount had LESS vibrations the the CS inserts? I thought that these inserts were the most tame approach to this and that full mounts or an engine damper would have more vibrations?

[Donutz]

Yes and no; the caveat is it depends on the mount. For example you could get a race mount in a very high duro that will shake your fillings loose. I'll say that the CPE 60 duro, AWR 65 duro, and the Street Unit vibrate less harshly. Don't read this to mean that they do not vibrate though. To me they seem to emit a lower frequency vibration, making the vibes more tolerable. CPE definitely vibes less than the inserts though, and holds more firmly. If you're in the east I can take you for a spin. I have some extra mounts though so it won't be a completely accurate comparison.

[Elbow]

Thanks Jason, I did a quick read up on the CP-E with the 60 Duro and it appears that it's a bit more mild. Unfortunately I live north of the GTA but I do appreciate the offer. I will have see if I can find a deal on a CP-E mm perhaps in the future. I took a quick drive at lunch with the A/C on, at idle it can be felt through the seat, steering wheel and pedals. The steering wheel visibly shakes when the A/C kicks in! I think there is more going on here for some reason. Thanks again all for the responces, my quest continues.