Most engine wear on any engine occurs at startup with that said the R series Toyota engines such as the 18R,20R and 22R all use a timing chain which it's tension is supplied by hydraulically driven timing chain tensioner which has it's oil pressure build up few seconds after the engine has started therefore the timing chain rubs on the driver's side brown colored nylon/plastic timing chain dampener or guide and after so many miles (140-170 000 miles in the city with the average 4 starts per day) the driver's side guide breaks through causing the chain to rub on the timing chain cover for the first few seconds upon startup and when driving in 5th gear and letting off the gas.
Usually by this point the other timing components such as the camshaft sprocket,crankshaft sprocket and chain have their specs out of tolerance and hence must be replaced as well.The tensioner sometimes sticks due to dirt build up and other problems arise as well and must be replaced as well,all of those parts are sold in the aftermarket world as a "timing chain kit" which also include gaskets and a front oil crankshaft seal.Toyota on the other hand for some reason does not sell the parts as a kit but as individual parts which would cost around $400+ and from all of the reading I have done on many Toyota 4-Runner/pickup discussion sites I have come to the conclusion that many experienced off-roaders who cannot afford to buy all of the genuine Toyota timing parts instead buy the chain and tensioner from Toyota and the other parts from aftermarket as a kit but of course don't use the aftermarket chain or tensioner.
The best brand of aftermarket timing chain parts to use on the 20R & 22R series Toyota motors are:
http://www.engnbldr.com/ToyotaHotlicks.htm
http://www.22r.biz/
http://www.rpmrons.com/toyotatiming.html
http://www.npr-america.com/index.htm
http://www.autotoyotaparts.com/toyota-truck-parts.html
http://www.toyota-engine-parts.com/
http://www.europeanautomotive.com
and if you choose to buy from Toyota these places have the best prices in the USA & probably the whole world:
http://www.1sttoyotaparts.com/partscat.html (10% shipping)
http://www.toyotadiscountparts.com (free shipping with $100 & up)
http://www.Toyotaparts4U.com
http://www.toyotaofplano.com
Other ways to check timing chain wear are:
http://www.misterfixit.com/chanslop.htm
you can also remove the valve cover and take a flashlight and see if the driver's side timing chain dampener or guide wore through.
You can bend 1 to all 8 valves and have timing cover eaten through if you wait and then coolant and oil mix together to give you butterflies in you stomach.You can do a fluid analysis on your engine oil by going to any Caterpillar and buying a fluid analysis kit for around $15-20 and taking a sample of your old oil.
Finally these sites explain the timing chain replacement well:
http://yotarepair.com/22R%20timingchain.html
http://www.4crawler.com/4x4/CheapTri...ingChain.shtml
http://www.4x4wire.com/toyota/maintenance/timingchain/
Sidney
Repairs tv's,vcr's,home/car audio out of my home
E-mail:sidneybek@yahoo.com
Dartmouth,Nova Scotia
Canada
1985 Toyota 4-Runner,22R-E,W56,RN60LV-MSEK,rusted rear step/towing chrome bumper with 243 000 KM
timing chain parts
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