March 2024

Toyota Corolla Start-up rattle fix

My Toyota Corolla 2010 started to make a strange rattle sound at cold start. It's a common problem and on youtube you can find many Toyota Corolla owners describing this problem. Toyota itself claims that this might be due to a problem with the VVT (variable valve timing) cam-gear and the fix would be to replace this part. I am not really sure that this true or that there is just a single cause for this start-up rattle. My theory is that the fault on my car was due to the chain hitting the case and rattling for a second at startup. In any case I don't know the exact mechanical cause but I know the symptoms and I know that it was possible to fix this at a cost of 10$ without visiting a Toyota garage.

a view of the corolla vvt gear with chain and camshaft. I never opened my engine. This is a picture from another car and you can see that there is a chain driving the camshaft.

The symptoms of the start-up rattle:

It was more likely to happen during the winter than during the summer. During the summer I would hear this rattle sound maybe once a month while on cold winter days it would appear at least at every second start-up of the cold engine.
It's a very short rattle sound. It sounds like a loose chain hitting a metal housing.
I have recorded the rattle sound and you can listen to it here: toyota-corolla-2010-start-up-rattle-sound.mp3. You can also compare this to a normal start-up without the rattle sound: toyota-corolla-2010-normal-start-up-sound.mp3
The problem started when the car had a milage of about 90000 km. I drove around with this problem for 3 years until I was able to fix this with an oil additive. I had also contacted a toyota garage to get their opinion. They thought that it was an urgent problem but I never bought into this because it happens only for a very short time at cold start.

In other words my problem was maybe related to the viscosity of the oil and/or sludge and gum deposits on the chain or the chain tensioner. I fixed it by adding a bottle of "Rislone Engine Treatment" (part number 34102) to the oil. This might have improved the oil flow and disolved some deposits. I added it after a fresh engine oil change and at that point the oil level was already at max. So adding one bottle of this Engine Treatment liquid resulted in slightly too much oil volume. The rattle disappeared after I had driven about 30km over 3 days (the last rattle was on the 3rd day after adding Rislone and it has not come back since). I added the "Rislone Engine Treatment" during the winter months when I would normally observe this start-up rattle problem very frequently. I have now driven for more than a month without ever hearing the start-up rattle and I am faily confident that the problem is resloved.

corolla: add Rislone Engine Treatment to fix start-up rattle problem

Rislone Engine Treatment bottle front and back, part number: 34102

I will leave the Rislone Engine Treatment in the engine for few more weeks and then I will do an oil change around mid March (at that point I will have driven about 350km with Rislone Engine Treatment in the oil). After the oil change I will not add anything back because I believe that this Rislone Engine Treatment has actually disolved some deposits somewhere and it should be a permanent fix to the problem. If it does not work out as planed and the rattle comes ever back then I would update this article and let you know.

References

SDS, Safety Data Sheet, Rislone Engine Treatment, It does not specify the exact composition. It's basically some kind of mineral oil. I can't really say that there is a significant difference between Rislone Engine Treatment and motor oil when I put a bit between fingers to test the viscosity. Rislone Engine Treatment might be a little thinner than normal oil but it's hard to tell. It smells different.