Diesel INTAKE noise??

[SafeAirOne]

2 years ago, I changed the stock air filter assembly on my 2.5 NA diesel ($45 air filters) to a Toyota air filter assembly ($9 air filters). I used a rigid, thin-wall aviation air intake hose between the filter assembly and intake manifold instead of the too-short stock air intake hose.

I couldn't believe how LOUD the intake was with the new setup. I ended up wrapping the intake hose with foam-rubber pipe insulation, which quieted it down quite a bit.

Well, the other night I removed the intake hose and showed a friend how loud it was with the hose off. He said (and I agree) that it sounds a bit like an exhaust sound coming from the intake manifold.

Now I'm wondering if a rocker/valve clearance issue might be causing exhaust noise in the intake manifold. That would be nice, as it's a relatively easy fix. Also, I've never changed the timing belt on this engine (no timing specialty tools). This engine was one of Les' Loft items 4 years ago, so I don't know how many miles are on it.

Anyone ever experienced something like this on a diesel? Are diesels normally noisy intake-wise?

[Tim Smith]

The good news is, no timing belt. Although, in your case, that might also be the bad news...

No ideas on the excessive noise.

[SafeAirOne]

The good news is, no timing belt. Although, in your case, that might also be the bad news...

Is the good news that it's not a timing belt issue (I hope), or that I have no timing belt? I should have clarified--its a 2.5 diesel. As a matter of fact, when I bought the engine from RN in 2004, I bought a replacement timing belt which sits in my box-o-spares in the garage right now.

[Tim Smith]

Sorry, I was being facetious. There is no timing belt but rather a timing chain on the 2.25 or 2.5 block.

The good news is that the chances of it skipping a tooth are pretty rare. Also the good news is that they last for ages longer than a belt.

The bad news is that if it has stretched, then maybe there is a bunch more mileage on your motor than you realize. Although this statement might be a bit of a stretch too, so take it with a grain of salt.

I'd be surprised it the timing was leaving your exhaust valves open, thus making more noise. I'd be less surprised to find that an intake valve or two isn't seating too well and is letting a little "bang" out the intake. Maybe the valves are too tight?

[Moose]

The 2.25 has a chain, the 2.5 has a belt. If the belt on it now has been in there for the four years you've been running the engine, and who knows how long before that, it is way past time for new timing belt. If it breaks, you are looking at a lot more $$$$ then you would have to spend on the timing pin.

Any chance you still have the original filter assembly? Maybe swap it back on and see if it is not so loud. They are not the quietest engine, but they are not too bad.

Brett

[Tim Smith]

The 2.25 has a chain, the 2.5 has a belt.

Really? I had no idea.

[SafeAirOne]

If the belt on it now has been in there for the four years you've been running the engine, and who knows how long before that, it is way past time for new timing belt. If it breaks, you are looking at a lot more $$$$ then you would have to spend on the timing pin.

Yeah. My original intention was to change it right after I installed the engine 4 years ago. Instead I drove the truck 3000 miles from the top right corner of the country to the bottom left. I just haven't had the motivation to tackle the project since. Plus, I figure that there's not as much risk of stripping teeth off the belt with a sudden burst of "power" (note quotation marks) with a 2.5 NA diesel.

Any chance you still have the original filter assembly? Maybe swap it back on and see if it is not so loud.

It won't be as loud, I'm sure of that--The original intake hose (I used the one off the originally-fitted 2.6 engine) contained all the noise. It's the same thick hose used on the 2.25 petrol.

Maybe the valves are too tight?

Thats EXACTLY what I'm hoping for. I'll find out in the next few weekends.

[junkyddog11]

The 2.5 is very noisy through the intake. If the valve clearance was off enough to hear exhaust it wouldn't run. It is entirely possible that the timing is off with a "relaxed" belt but that will not make it any quieter either.

Before any diesel install I change the belt (other than new engines) as it gives you a fresh place to start. You wouldn't like what happens when they break and it has nothing to do with "sudden burst of power" and has everything to do with time as much as mileage. Cheap insurance.