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Am I nuts to replace the seals when I replace the timing belt?

My 2008 Solara (3MZ-FE engine) just crossed 90k miles, so I am planning to replace the timing belt. I
am considering replacing the cam and crank seals, and maybe the oil pump
seal, as long as I have things apart. But a voice in my head says “if it ain’t
broke, don’t fix it.” I have not replaced shaft seals before, but have researched
the seal replacement thoroughly, am a decent backyard mechanic, and don’t
need the car back on the road immediately if I need to get assistance. My
question: should I leave well enough alone, or is this a manageable

Rubber is a degradeable product and the seals are 10 years old. It would be foolish not to replace them.

They may not be leaking now but considering the age, may start leaking a week after you replace the timing belt.


You would be WISE to replace those seals you mentioned

In addition, I would also replace the tensioner and idler

Don’t be surprised if the water pump also looks crusty, when you get in there

I recommend you get a complete timing belt kit, which includes the water pump

You want everything under the cover good to go, until the next timing belt job


It is always a little scary to do a task for the first time. You did your research, you can let the car sit if necessary, you saw the advice given by knowledgeable (and professional) posters. Go for it. It isn’t rocket surgery. Change the seals. Good Luck!

Check the time interval for timing belt replacement. Gates lists 100,000 miles as the timing belt replacement interval, but mentions no time interval. My Accord V6 is supposed to be changed at 105,000 miles or 7 years. I would be surprised if Toyota does not recommend a time around 7 years. I mention this for your next timing belt change if you still own the car, and to encourage you to do it quickly this time.

I would buy the full kit with the water pump as suggested by @db4690. You have to remove the timing belt to replace the water pump, and that is likely to occur before your car is 17 years old. Then you have to put a new timing belt in prematurely. This is also a great time to change the coolant.

Toyota also has a time interval for timing belts, and OP’s car is already overdue by time

Speaking of the water pump, on my car, which has a 1MZ-FE engine, a slightly smaller version of OP’s 3MZ-FE engine, I didn’t know the water pump was crusty until I had that timing cover off. But it didn’t matter, because I had purchased the full kit, anyways

Some seals are user friendly and some aren’t. Those with a metal flange are usually easily installed and trouble free while those that need to be sunk into a well, especially those without metal outer shells are prone to failure for the inexperienced. The confined working space and often lack of ideal tools compounds the problems also. I recall some Ford 1.8L seals that were a real pain while the cheaper after market seals were quick, easy and trouble free. It is advisable to replace the seals and all the other parts that come in a good timing belt kit.