Engine rattle, right side

[JohnCW Lurker Find all posts View Profile Close JohnCW]

Share this experience as anyone with a 120 is likely to have a similar underlying issue given the age of the vehicle.

For ages I've been trying to work out where bad engine 'rattle' was coming from. It was more pronounced on the right hand side of the vehicle, and clearly induction related as it varied with throttle response (worse with just light throttle). To make a long story short, finally found and fixed the problem.

The problem is where the air intake which sits inside the front mudguard goes through the guard and into the airbox (filter box). There are two foam seals that had totally disintegrated over time. One seals the intake into the guard, the other seals the intake into the airbox. Both had totally disintegrated allowing the intake to both leak and rattle at this point. I would expect any vehicle of similar age (2004 model) to have exactly the same issue.

The seals are not available without buying a whole new airbox, so a $20 tube of black sealant was used to create both seals. The reduction in engine noise is staggering. The inner mudguard liner must be removed to do the job. Not difficulty, just fiddly. Tip, buy a pack of non genuine liner clips and have them on hand before attempting the job (genuine ones are outrageously expensive). They have a round head, square 8mm back, and two 'barbs'. The clips can be a turd to get out and some will get damaged, especially the four up under where the flairs bolt on. They are so difficult to get at I just cut the heads off and pushed them out the back.

[ptommo59 Senior Member Find all posts View Profile Close ptommo59]

Funny the issue you experienced is still happening on the newer Prados as well.

See this video from Nudawading Toyota Toyota Prado150 Dash Rattle, Driver's Side. Watch this First, Do Not Remove the Dash. - YouTube which shows the issue and fix that they have come up with which may also be applicable for the 120 even though the filter parts will be a bit different.

If nothing else I think it will help explain what you are talking about.

[JohnCW Lurker Find all posts View Profile Close JohnCW]

Yep, the video highlights exactly the issue. Pretty much identical airbox design (mine just has an addition bolt on bit on the lid). He was lucky he could replicate the problem when stationary, I couldn't, which made it so much harder to track down.

P.S. Not overly impressed with his repair method. Might be ok if you're paying someone by the hour. If you're doing it yourself and want a permanent solution, reckon my methodology of removing the inner liner and airbox is vastly superior. I used a ring of Sikaflex 221 to both position the intake into the guard, as well as seal the intake into the airbox 'collar', bolting the airbox back in place and letting it all set overnight. Both connections have foam seals which had completely broken down. The airbox can still be removed if needed by separating the taper fit 'collar'.

Also, the little one way rubber 'flapper' valve at the bottom front of the airbox. It simply twists off, clearly so it can be serviced. But because, like the car in the video, mine was hidden behind the second battery it had never been serviced in nearly 20 years. Mine was absolutely choked up with crap and completely sealed off. There are other drain holes in the main body of the airbox so not exactly sure why this additional one-way valve is fitted where it is. But it certainly needs to be routinely serviced to keep it clean to perform whatever function it's supposed to do.

[ptommo59 Senior Member Find all posts View Profile Close ptommo59]

The little one way rubber 'flapper' valve at the bottom front of the airbox you mentioned is the same as the scupper valves used on boats. It allows water that makes its way into the airbox via the air intake out but not back in through that path. The recess its mounted on is the lowest point in the airbox so not only water but dust and debris make their way there. Without removing the air filter or valve you can clear the residual water and/or dirt from the recess by squeezing the outer edge of the lips so they open. They do eventually perish and not seal effectively so many people that fit snorkels seal them up if intending to do deep water crossings.

[JohnCW Lurker Find all posts View Profile Close JohnCW]

A little more on this issue. Since fixing the intake leak I had to tow the caravan around 400 kilometers to where it is stored. And obviously drive home unloaded. Under both cases I felt the car definitely ran better and was more powerful. First to admit that this may just be an illusion due to the much quieter motor, but even taking that into account, it was impression performance was noticeably improved.

They obviously design that complex airbox with a 'spinner' in the intake throat for a reason. I'm familiar with the ram air effect of airbox frequencies on high performance petrol engines, perhaps its the same with diesels.