grm405

I just replaced the tensioner on my 92 SC400 and thought it would be helpful to write it up the procedure in more detail than I could find it in these forums. It took me 3 ½ hours, about 2 ½ to remove the old one and a hour to put everything back together. Obviously, I learned a lot in the disassembly process and once you know where all the bolts are, it is a lot easier.

First, the parts. Gates now makes an EXACT replacement tensioner which fits without modification. The part number is 39080. Other aftermarket tensioners require modification and really don’t fit exactly, but this one does. I bought it from Amazon for $118, about twice the cost of the “don’t really fit ones”, but a lot cheaper than the OEM Lexus part. It really does fit.

I used a write up by LOMIS dated 2004 as a guide. It was accurate, but lacking in detail. The detail would have saved me a couple hours so here it is.

1: Remove the battery ground terminal. Lots safer than removing the positive terminal.

2: Remove the air filter housing and connector. There are 3 bolts holding the filter housing in and one on the plastic connector. That is a hidden one behind the engine, not visible but found by feel. There are 2 hoses and one electrical plug on the housing and connector. Loosen the hose clamps and pry off the connector from the throttle body. Mine was really stuck and I had to remove the TRAC cover to use a screwdriver to pry it off.

3: Remove the center wire harness cover (2 bolts). Remove the left coil (2 bolts under it and one on the right side). Just push it aside, no need to disconnect.

4: Remove the Passenger side wire cover (1 bolt) and the top timing cover (3 bolts). No problems here.

5: Remove the serpentine belt using a 14mm ratchet turning CCW to release tension on the belt. You need this off to see the bolts on the lower timing cover for the next step.

6: Remove the 5 bolts holding the lower timing cover on. The 5th one is hidden under the bottom edge of the cover behind the tensioner pulley. You probably can’t see it but you can feel it. The lower cover will now be loose and can be bent/moved to get the tensioner off.

7: Remove the 3 nuts and one bolt holding the tensioner on. The big nut on a stud is the top one holding the alternator on also.

8: Remove the bottom bolt on the alternator and slide the alternator forward to remove. That big nut is on a long stud, not a bolt. Slide the alternator off forward and let it hang. Spent an hour looking for the other end of the bolt so I could remove it until I decided it must be a stud. It is. Yes, there is room.

9: Remove the tensioner by pulling forward off the stud, bending/sliding the lower timing cover as necessary. Slide the new tensioner on in the same fashion. Not all that hard at this point. And mine fit exactly like the OEM one.

10: Put things back together in the reverse of the above steps.

11: Putting the belt on requires turning the tensioner CCW just as before, but hopefully it takes more force than removal. Mine certainly did.

11: Make sure you hook up all the hoses you removed, both intentionally and accidently. I found 2 which I had to trace and replace.

Mine now does not loudly “HUMM…” when I turn the AC on, something the Gaterback belt does instead of squealing. Totally silent when I turn the AC on. I deem the operation a success. The old tensioner put in its 22 years and just got tired.

I found one part underneath the car and found no place for it. Looks like a part of a rubber mount, but didn’t fit the only rubber mounts I removed, the air filter box mounts. Oh well, I suppose I will find where it goes someday….. maybe.

Gerry