Supra Crank Pulley Squeal, Not Fan Belt!
Does your Mk4 Toyota Supra squeal like a pig when you start it or rev the engine? Could it be the fan belt slipping? As you've found this page, I thought you might be interested to read about the Crank Pulley on my Mk4 Non-Turbo Toyota Supra.
My Supra was showing the usual signs of the fan belt slipping. It made a squeal when it was first started up, and a slight screech when blipping the accelerator. It also made a funny squeaking screechy noise when maneuvering or when the engine was labouring. More so when steering as the power steering pump put more load through the belt.
The problem turned out to be the Crank Pulley, NOT the fan belt. This is the wheel on the end of the crank that turns the fan belt, in case you didn't know. :-)
The stock Toyota crank pulleys are made of more than one part separated by a rubber damper designed to protect the crank from vibration and wear. When the crank pulley gets old, the rubber wears and the two parts slip, causing the squealing noise. If you don't replace it, it could fly off and smash up other bits in the engine bay.
Prove this is the problem by painting a line of tipp-ex across the two parts, then rev the engine and check to see if the tipp-ex marks still line up. You can reach down to get to it, through the gap marked with the arrow in the picture. Even after simply starting the engine on my Supra, the two parts had slipped and the tipp-ex marks didn't line up any more.
After the old pulley was removed, it turned out to be so worn, the outer wheel was literally flopping about on the inner one!
New Crank Pulley
Don't be tempted to buy one of the one-piece aluminium light-weight crank pulleys that claim to increase BHP, stick with an original Toyota one, or you risk wearing out your crank bearings. Yes, OEM Toyota crank pulleys cost a fortune, but shop around and you can find a cheaper one. Toyota quoted my £300 for one, but I found a brand new freshly imported genuine Toyota one for about £160. As long as the fan belt isn't fairly new, you might as well change that at the same time.
That solved the problem for me!
Crank Pulley/Fan Belt Details and Pictures
Mark the front of the crank pulley with Tipp-Ex, like so
Reach through to the crank pulley here
New genuine Toyota Supra crank pulley
New genuine Toyota Supra fan belt
Worn crank pulley totally loose around rubber ring marked with in red