Ok so Mine was installed in March '21 on my '17 with 55k miles(61k when replaced) and a month later I started hearing the very low noise when It was in gear w AC on/low fan setting it was noticiable pulling away cold in morning out of the garage. Eventually it got worse during a big road trip cross-country and the noise was replicated by turning AC off when the now semi-loud noise would instantly go away. I was blaming my AC clutch and searching forums for that, but FINALLY figured it all out when I opened the hood after putting parking brake ON and IN GEAR w AC ON. Looked underhood and boom......when AC comp cycled it TOTALLY induced some sort of harmonic vibe from the main belt drive to to blower belt drive. The chinese (black) tensioner it ships with flaps back n forth and its totally obvious the outer belt flaps around wildly almost slapping the inner idlers. This happens ONLY when AC clutch is locked in-cycle. Apparently the 'supplied china tensioner' that happens to cross reference from a Mopar application for 15-20 y/o fwd 300c/jeeps is not rated correctly for our belt stiffness and the all silver one is. The silver EU part has a whole different design to the spring/housing.
My theory is that the belt length specified is SUPER stiff anyway before it breaks-in and the weaker spring in the supplied tensioner gives out from the initial belt stiffness quickly...as in several hundred miles it starts to display faint noise w AC running.
To start my repair story, after seeing this thread and coming to conclusion that it has to be it, I emailed Magnuson tech, he requested a movie of it(cell phone worked fine like 8sec vid, proof on invoice from dealer/installer) & they replied within a day that a replacement tensioner would be shipped. They also supplied a new idler pulley to put on the tensioner since they do not come w it installed. You can re-use the one on there I guess and take chances w another prob, or just use the new idler they also ship. Got it all 3-4 biz days later bc of weekend and starting the claim on a Friday. I was going to have local Socal dealer swap it since they were the o.g. auth installer, but bc the 1/2" drive socket square was starting to round off from me trying to mess w it(cheap china one sucks!) Technician said he wanted to CUT my belt and then remove the tensioner b/c he did not feel comfortable putting leverage on the magnuson specific water neck housing thats next to tensioner (he claims he could not use his breaker bar!!!.
Note: If water neck breaks its 60-90 days for new water neck or for ANY magnuson specific blower related parts so be carefull!) And also belts ...nobody stocks the belt locally in socal even.... so... I laughed in the techs general direction and went home and just did it myself. I had my son help me w a 3rd hand while i used my 2 hands to relieve tension on the Chinese junk while not hurting my belt or water neck w a cheater bar using my breaker bar that I wrapped tape around the drive to make it fit snug where it was starting to round-off. After completion in 20 minutes It was obvious that the magnuson install tech was trying to sheist me out of 3 hrs billable.
To add spice to story the same dealer had another 4R in there getting a blower done and they told me even the latest kits have the same Chinese tensioner inside!!! So...do yourself a favor if your looking to install one even thru a yoda stealership - BUY the $40-50 replacement tensioner from Magnuson AHEAD of install and have the tech use it instead. Its sad that Magnuson needs to be doing a recall on these and/or sending communication + matching # of correct better Tensioners as a supplement to each kit thats in inventory. Toyota people are very loyal and precise and Magnuson should be stepping up to show accountability. I even recommended to the dealer that they proactively order a few Tensioners as a precaution and invoice them out $00.00 IE; eat the cost or even just retail sell to the new customer...that would pay to not have to deal with the worry down the road.
Heres the Magnuson part#s for made in EU Tensioner I was shipped
# 56-50-53-012 Dayco 89280
....and the Idler that bolts on it
# 56-50-53-001 Dayco 89143 75mm 6rib
The Internet sells BOTH chinese and the made in EU on the box version under DAYCO brand # 89280 so choose wisely and only use an all silver one w made in EU on the box. The crappy one has black circle front and made in china is visible next to the 1/2" socket drive insert.
Some sources online show the china black one and some show pics of the better all silver tensioner. Its up to you to possibly find the right one for $30+ from rock auto, amazon, etc; im willing to bet Magnuson is the best bet since they know its a big problem now,..... but some of these posts prev show Magnuson sending out yet another black china version w the shallow 1/2" drive. Smfh??!! !!!
To play it safe bc belts arent stocked locally and bc chyna-virus has stuff backordered, I also bought a second blower belt from amazon jungle for $32 to be safe and ready:
Dayco Poly Rib V-Ribbed Belt (5060701)
To be clear here, the stealership service writer said maggie has had issues with the Tundra blowers also I believe its a coupler inside the case. Customers are having to pay x2 labour for installs bc the blower has to be completely taken apart to swap warranty couplers. The magnuson warranty does NOT cover ANY labor costs, only parts. Im willing to bet if Toyota still sold these under TRD name labor would be included. Maybee this is part/why Toyota quit selling them as an accessory. Just something to think about if your on the fence with getting a maggie. The upcoming '22+ Boosted OEM drivelines might be worth waiting for?
I love having 350hp/355tq now pushing 33's around it is totally worth it especially w the whine. But after spending 25years playing w cars one thing has never changed and that is that aftermarket stuff is rarely perfect, there is always something that screws up lol. Hope this helps.
