2005 3.5L cold startup rattle

[Mr Toad]

2005 3.5L rattle at startup when the weather turns cold, low 50s. Doesn’t do it in the summer when the overnight temperatures are warmer. Only lasts for a couple of minutes. The rattle gets quieter as the engine starts to warms up until it’s gone, like I said about 3 or 4 minutes. I read where the timing belt tensioner can loose its hydraulic oil and rattle, but this would rattle all the time, no oil seen around tensioner. I also read where the VTEC can wear to where it causes a rattle at startup but they say it only lasts for 2 seconds. The sound seems to be coming from under the intake manifold toward the belt (passenger) side of the engine. Everything runs great, no trouble codes.

Got me stumped, any ideas?

[Mr Toad]

OK, I am convinced it IS in fact the timing belt tensioner. I put my hand on the tensioner while it was rattling and felt it thumping at the same rate as the rattle. I think the reason it goes away after 3 or 4 minutes is because the belt warms up and runs smoother.

Tomorrow I am going to get a quote on all timing component replacement. I had it done 60k ago but that was also 10 years ago. Since they have to get in there to replace the tensioner they might as well do the whole thing.

[fdryer]

Are you describing the serpentine belt and its belt tensioner or timing belt hidden under the cover against road debris? The serp belt and tensioner are usually exposed for easy checking and maintenance when replacement is needed. The timing belt is hidden behind a timing belt cover with many parts removed before access to the timing belt. Serp and timing belt are driven by the crankshaft with the large crank pulley showing the serp belt. The timing belt is behind the serp belt and driven with a smaller toothed gear.

Here's one video to help; https://www.youtube.com/watch?v=1BzCEESMx50

[Mr Toad]

Took it to my favorite shop today and got a quote. $966 for complete job with OE AISIN kit includes all pulleys tensioner belt and water pump. Getting it done on Wednesday.

I could do it myself but I don’t want to hassle with the crank bolt. Beside, I am retired and have enough money for things like this. I would rather pay someone that still has to work to feed his family.

[Mr Toad]

Today was the appointment to get the timing components replaced. Got up early to get the car in first thing. Noticed when I started it there was no rattle even thought it was cold outside. Almost called the shop and called the whole thing off but I didn’t. When I got to the shop they informed me the parts weren’t there yet and should arrive sometime today. I told them I needed the car back tonight. They are closed for Thanksgiving until Monday. They said they wouldn’t start on it until the parts arrived. About 1pm they got the parts but didn’t want to start on it in case they couldn’t finish by quitting time so… I will bring it back in on Monday.
I was second-guessing myself if was really the tensioner so I took a closer look at it. I noticed the tensioner body is covered in dirty oil and everything around it is dry. That convinced me. I will be taking it in Monday.

[Mr Toad]

Finally got the timing kit installed. Nice and quiet now.