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| How to Diagnose Worn Engine Mounts (Page 1/1) |
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Brian A
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DEC 14, 05:12 PM
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How do you determine if your engine mounts need replacement?
My intake plenum moves about 3/4" forward and back between idling and accelerating. Normal? Failing engine mounts? Other?[This message has been edited by Brian A (edited 12-14-2025).]
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82-T/A [At Work]
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DEC 14, 06:26 PM
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| quote | Originally posted by Brian A:
How do you determine if your engine mounts need replacement?
My intake plenum moves about 3/4" forward and back between idling and accelerating. Normal? Failing engine mounts? Other?
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No, it should definitely not be doing that. More than likely, your "dog bone" is worn out, it's also called the torque strut or something. It's that dog bone looking thing that attaches to the rear most firewall against the trunk, and where the alternator is. You need to replace that.
But also, and honestly... at this point... 2025 almost 2026, any car that was made before 2000 probably has worn motor mounts. So if you're considering it, and don't mind the work, replace all the motor mounts. It's two transmission mounts, and one front engine mount... and then the dog bone on top. There is also the "shock absorber" for the V6, which is a little driveline absorber that helps take some force off the motor... I think I've only seen it on manual transmission cars, but it should fit all of them... and it could be on all the V6s. It's only on the V6 though.
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Brian A
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DEC 15, 12:20 AM
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Thanks for the response. Sounds like I need to replace the mounts. I vaguely recall noticing the damper; I’ll look for it specifically next time I’m under the car.
I can sometimes get a bit of a clunk when I let the clutch out when starting from a stop.
My dogbone appears to be okay. It has polyurethane bushings so is aftermarket. I’m not sure how old. The original dogbone is in a box of stuff that came with the car.
Yeah, sorry: the car is a 1987 GT with 5-sp and V6.[This message has been edited by Brian A (edited 12-15-2025).]
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82-T/A [At Work]
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DEC 15, 10:59 AM
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| quote | Originally posted by Brian A:
Thanks for the response. Sounds like I need to replace the mounts. I vaguely recall noticing the damper; I’ll look for it specifically next time I’m under the car.
I can sometimes get a bit of a clunk when I let the clutch out when starting from a stop.
My dogbone appears to be okay. It has polyurethane bushings so is aftermarket. I’m not sure how old. The original dogbone is in a box of stuff that came with the car.
Yeah, sorry: the car is a 1987 GT with 5-sp and V6.
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If it's clunking, it's very likely bad motor mounts.
I used to think poly engine strut was good, but all it really does is transfer vibration from the engine to the frame. I'd personally replace it with a new rubber one. But another thing that may be happening... check to make sure the bolts are tight. Sometimes if the bolts are loose... even if the engine strut is good, it may be moving back and forth within the mounting holes.
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Doug85GT
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DEC 15, 06:29 PM
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Often you can see the mount has come apart. I have had my transmission mounts fail. Just looking at the rear one with a flashlight I could see it was not aligned. It turns out both of my transmission mounts were bad. I have not had to replace an engine mount on two cars. I think the transmission mounts and dog bone take most of the torque load.
They are not too hard to replace. Put the rear of the car on jack stands, then put the jack with a cushion (such as a 2x4) under the transmission or use an engine crane if you have one. Support the weight of the transmission and engine with the jack/crane, remove the nuts on one mount, raise the transmission about an inch, swap out one mount. Lower it back down and install the rest of the nuts but leave the nuts loose. Repeat with the other transmission mount. Once you have both of the mounts replaced, then tighten down all the nuts. Repeat if the engine mount needs to be replaced too.
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Brian A
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DEC 16, 10:11 AM
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I really appreciate the detailed information. Thank you. The installation instructions will be helpful.
I checked the dog bone. Superficially, it looks fine, but I think I better remove it to inspect the condition of its black (polyurethane) bushings.[This message has been edited by Brian A (edited 12-16-2025).]
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