..certainly sounds like something is loose ..or maybe the tensioner is sticking/jamming and allowing the belt to go slack.... for 5mins anyway!.... never heard of that but..its a maybe. At the minimum you wanna be getting the covers off quick and having a look ... Im sure that will tell you what you need to know...

 

Belts do stretch with time, and perhaps the tensioner pulley isn't doing it's job as well as it should, and or the belt was never tensioned the Toyota way. If were to go through the trouble of taking it apart I would replace the belt and tensioner pulleys as a minimum.

 

The upper timing belt cover is pictured below. It looks like there is a hole for inserting a 14mm socket to get at the tensioner bolt. The hole should have a fairly-easy-to-remove rubber plug in it. Here is the procedure for setting the tension, thanks to forum member "Blue":

Loosen the tensioner bolt enough so that the spring pulls the belt tight.

Remove the spark plugs. Also ensure the transmission is in neutral.

Place lower plastic housing in place (no bolts) and install [harmonic balancer, a.k.a. crankshaft pulley] hand tight and turn motor using 19mm ratchet for 1 and 7/8 turns (DO NOT TURN CCW AS BELT CAN JUMP) . Align the 45 degree BTDC "lonely" triangle with the tickmark in the pulley. At this point of 45 degrees BTDC, The springs in the head will now be at maximum resistance causing the tensioner to be stretched at its maximum. Lock down the tensioner bolt (14mm with torque ~ 35 to 40 ft-lbs). FYI if the belt tension is too tight, the bearings in the idler pulleys will whine when the engine comes up to temperature and stretches the belt from thermal expansion of the block and head).

For the illustration showing the 45 degree BTDC mark, see https://www.rav4world.com/forums/94-4-1-d-i-y-modifications/56986-diy-timing-belt-2.html

My Honda Civics (1991, 1993, 2003) had a hole in the timing belt cover like the one pictured. On the Civics, I could tension the belt through the hole. Though I did this maybe once. The Rav4's have a fair amount of interference. Notably, the Rav's have a bracket bolted to (a) the engine block and (b) an engine mount that may make it difficult to get to the hole. The bracket may obstruct access to the hole.

If you cannot get to the tensioner bolt using the above, then yes, you are stuck doing a mini timing belt job, which argues for doing a full blown timing belt job (new timing belt, tensioner, water pump, idler pulley, two oil pump seals, cam seal, crank seal).

I doubt re-setting the tension will change anything, though.

 

Subscribed. Experiencing the same belt slap after doing my belt earlier this year. Suspect that it's either too tight or loose..

 

I'm having similar problems on mine after I replaced the belt and water pump. Now after driving about 30 miles on the new belt, my check engine light has come one.

 

Y'all make sure you are using high-quality belts. Gates or OEM would be my choice if I had to do it again. Cloyes used to make great timing chain-sets for SBCs, but IDK about their belts. Rockauto dot com. {Cheap belts are known to stretch}

Align and tighten them properly. Replace the tensioner (and another pulley, so a "belt kit") and water pump if not done already.