RS Motor Mounts DIY w/ Pics and Part Nos by Scottslaw

14 minute read

RS Motor Mounts DIY w/ Pics and Part Nos 

Compliments of Scottslaw @ 6speedonline.com

9-19-2011

I just installed my RS motor mounts last night and I love them! The DIY on this is pretty straightforward, but there are some "gotchas," particularly because there are no published instructions I could find for installing these on a 996tt.

As some of you may know, the RS mounts were originally designed for a 964 application and I believe the 993 RS, and for this reason there are no instructions that say which washers, spacers, and bolts to use to get them to work properly with the 996tt chassis. Specifically, you have to be very careful to get the stack height of the mount correct with all the right washers and spacers, in the right order, or the engine will not be sitting at the right level and/or there could be extra stress on the engine carrier. As far as I know, there is no "kit" from Porsche with all the correct washers, spacers, and bolts for a 996tt, so the vendors that sell these kits assemble them on their own. I bought my "kit" from Suncoast, but it came with at least 7-8 extra washers and bolts that are designed for use on a 964/993, so I had to figure out what to use and what not to use.

That is where Kevin at UMW came in. I saw in a post on another forum that he stocks the kit with all the correct hardware, and he was kind enough to tell me the correct order of everything, and what to use and what not to use, even though I didn't even buy his kit. Also, he did all this after 9:00pm. Way above and beyond (Thanks Kevin).

Anyway, on with the DIY. Here are the parts you will need:

1. 2 RS motor mounts: 964-375-043-81.
2. 2 longer, silver motor mount through bolts (the 964/993 RS bolts are shorter and will not work) 900-082-118-01.
3. 2 18mm motor mount through bolt nuts (these are identical to the stock 996tt nuts, so you can reuse your existing nuts if you are so inclined (insert beavis and butthead laugh here). 999-084-215-01.
4. 4 large, gold-colored, curved washers, 2 per mount (one on top of the mount and one on the bottom of the mount, immediately adjacent to the rubber of the mount, with the concave surfaces facing the mount). 901-305-311-00.
5. 2 grey, small diameter, but very thick (5mm) spacers/washers, one per mount. These go between the bottom gold washer and the engine carrier. 999-025-74-01.
6. 4 top-side motor mount bolts (the ones that hold down the mount to the chassis), two per side. These too are identical to the stock bolts on the top of stock motor mounts, so you can re-use the stock bolts if desired. 900-378-159-01.

Picture 1 shows an exploded view of all of these parts in the “stack” (ignore the two small gold-colored washers that are to the right and left of the two silver top-mount bolts in the picture, as you do not need these)

Tools: (1) assorted sockets (you will need at least two 18mm sockets or one 18mm socket and an 18mm wrench); (2) a nice long socket extension for the bottom nuts to achieve good wrench clearance from underneath (I used a 12-inch extension, but smaller could get the job done); (3) an assortment of short extensions to get access to the bolts on the top side of the engine mount; (4) a floor jack with either a hockey puck or small piece of wood to place between the jack and the engine case; and (5) a helper to hold the top of the motor mount bolt with a socket/wrench so it doesn’t spin while you tighten the bottom 18mm nut.

Step 1: Unclip both driver and passenger side boost hoses from the y-pipe for better clearance. No need to unclip the side that goes to the intercooler, as those are a pain to get off and on with the bumper on the car.
Step 2: Remove airbox by: (1) removing the 13 mm (I think) hex head bolt holding the airbox to the chassis; and (2) removing the large hose clamp holding the MAF sensor tube to the driver’s side intake ducting. Unclip the MAF sensor harness connector from the MAF sensor and lay the connector with the wiring out of the way (no need to actually remove the sensor from the MAF tube). Rotate the passenger-side of the airbox straight up, and maneuver it out from the engine bay by sliding the MAF tube out from under the driver's side boost hose (rotating the airbox is a great trick to get the airboxout quickly, and avoids the need to man-handle the airbox out from the engine). Picture 2 below shows the engine sans airbox, exposing the two motor mounts on the edges of where the airbox was sitting.

Step 3: Chock the front wheels and jack up the car from the engine, using the hockey puck or wood block between the jack and the engine case. Picture 3 shows the location I always use to jack the engine up (it is dead center on the seam where the case halves come together, near the extreme rear of the engine case). Be careful not to let the metal of the jack contact the case, or let the jack or the hockey puck put pressure on the metal lines running from side to side at the rear of the engine case. Lift the engine just enough so that the weight of the engine is resting on the jack instead of the motor mounts. To be safe, I would place some jack stands at strategic locations under robust suspension members, just in case the engine comes down for some reason while you are under it (i.e., jack failure, earthquake, wife pushes car over onto you when she finds out how much you spent on motor mounts, etc….)

Step 4: Go under the car, locate the large 18mm nuts that hold the ends of the engine mountthrough bolts to the engine carrier, and remove them using a 12-inch socket extension and 18mm socket. See Picture 4. If you can see/feel the engine moving as you start to remove this nut, then you have probably not jacked up the engine enough to take the weight off the engine mounts. You should be able to remove these nuts and the engine should stay in essentially the same location, if you have jacked the engine to the correct height.

Step 5: With the nuts off the bolts and the engine supported by the jack, you should now be able to remove the bolts that hold the engine mounts to the chassis. These are accessed through the engine compartment, and there are two per mount. There are no corresponding nuts, as these bolts thread directly into the chassis. I used a small 1-inch extension to get good clearance over the top of the motor mount. Once these bolts are removed you can wiggle the mounts out of the engine compartment. It may help to push on the boost hoses that have been unclipped from the y-pipe to get a bit more clearance. Picture 5 shows the deflection I could induce in the stock (88k miles) mounts with my bare hands…I couldn’t see any rips, leaking, or other obvious damage, but I can’t imagine the mounts should be that loose. By the way, I could not get ANY deflection from the rs mounts when I tried the same test (the felt completely solid in comparison).

Step 6: Now its time to insert the rs mounts. Again, they should be assembled in the order shown in the first picture, except leave the nut off as that goes on the other side of the engine carrier. Picture 6 shows another view of the correct “stack” orientation, and Picture 7 shows the stack going in. Again, the order is large silver through-bolt, large gold washer with concave surface facing rubber, motor mount, large gold washer with concave surface facing motor mount, thick grey washer/spacer, engine carrier, then finally the 18mm nut. Tighten the two bolts that hold each mount to the chassis (4 in total) to 23 ft. lbs. I tightened a little bit more, but just by a hair.

Step 7: Now that the mounts are fastened to the chassis, go under the car and tighten the 18mm nut that holds the motor mount to the engine carrier (remember, there is no washer between this nut and the carrier). Convince your smoking hot significant other to take a break from sewing “MC Hammer” pants for your 7-year old for “90’s Day” at school (you can’t make this stuff up…see Picture 8…note the red pin cushion attached to her wrist!). Have your helper hold an 18 mm socket or wrench to the top of the motor mount bolt to keep it from spinning while you tighten the bottom 18mm nut to 63 ft lbs.

Step 8: Double check the torque specs and that everything is tight and in line, and after removing any jacks or wood blocks installed as a safety precaution, SLOWLY start to lower the engine, watching the carrier and mounts to make sure the load is distributed on the mounts/carrier, and that there are no gaps between the chassis/mounts/carrier. Reinstall the airbox, clip in the maf sensor connector, reattach the boost hoses to the y-pipe, and you are in business!

As for driving impressions, the car definitely feels more solid and planted, and that is with driving the car at only 6/10th’s at the most. If you are a track guy I’m sure you will perceive an even greater difference. As for additional NHV (noise, harshness, vibration), well, I can honestly say if there is any increased NHV I can’t tell if it is real or just imagined because I’m now paying attention. In other words, any increase in NHV is negligible in my opinion. This is especially the case if you already have an exhaust, as an increase in sound or vibration is going to be completely overwhelmed by the noise and vibration from the exhaust. Perhaps if you are bone stock, you would tell a difference, but I would be shocked if the NHV from these mounts bothered anyone who already has an aftermarket exhaust. All in all a very sold mod. Next up, pss9’s (my car is going on my buddy’s lift this week!).

9-21-2011

Thanks, its an easy diy, but with me, I really appreciate detailed instructions. I can follow good instructions, but none of this stuff is all that intuitive for me, as it seems to be for many people on this forum who have been wrenching for years. The first time I changed oil in any car of mine was when I went to to dealer for an oil change on my first boxster years ago, and drove straight home and searched the forums for a diy after hearing the outrageous quote. I actually really, really enjoy doing stuff myself, as I find it to be a nice, therapeutic departure from my day job (plus, I'm kind of cheap!). I should have skipped law school and instead went to UTI! I'm going to document my pss9 install as well.

10-5-2011

Interesting. I did not recieve any instructions from Suncoast, nor did I ask. I will note that the illustration you attached appears to have a different engine carrier than the 996tt (it looks like a 964/993 carrier to me, but I could be wrong), so I would question whether that illustration is truly representative of the 996tt installation, or simply an illustration of the 993/964 application. I got my "stack" information from Kevin at UMW who assembles these kits for use on our cars. In any event, I can't imagine using that waster will hurt anything because it will not change the "stack height" of the mount relative to the engine/engine carrier. All the insertion of that washer will do is reduce the number of threads on the mount bolt that extend below the engine carrier (which isn't a big deal at all becaues there is more than enough thread on the end of the longer 996tt bolts to permit full installation of the bottom nut). My take is that you could probably use the washer with no ill effects, but I left it off since Kevin said it was not needed, and from my inspection of the interface between the large gold washer and the head of the through bolt, there is absolutely no need for a washer there (but that's just a guess).

One other clarification....in the attached illustration it indicates the use of a small washer for each of the bolts (two per mount) that hold the mount to the chassis. I would not use those because upon examination, you might not get good thread penetration into the chasssis with those washers installed (not that these bolts thread directly into the aluminum "spacer" that sits in the engine compartment, there is no nut that secures the mount to the chassis). After all, the bolt hole "flange" at this location for the rs mount is approximately the same thickness of the oem bolt hole flange, and the 996tt manual shows that no washers are used at this location and the rs mount kit bolts are the same lenght as the oem bolts, suggesting to me a risk of insufficient thread penetration if you use washers in conjunction with those bolts. Hope that makes sense (it probably will make more sense after you remove the oem mount and compare its shape to the rs mount).

Thanks for adding to the thread! (P.S. For reference I've added a pic I found on another forum that was taken by Kevin (I hope he doesn't mind) that clearly shows his installation, and that the two side bolt washers and the silver washer atop the gold curved washer are not installed).

10-7-2011

23 ft. lbs. for the two top-side bolts, and 63 ft. lbs. for the bottom 18mm nuts.