Question about 1999 Toyota Avalon

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What can cause a noisy engine? It sounds like the muffler, but is coming from under the engine versus the rear underside.

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  • mpolimus Jul 16, 2009

    That was my first thought. It must be the manifold on the bottom side of the engine. I'm betting this is gonna cost a small fortune ...

  • mpolimus Jul 16, 2009

    That was my first thought. It must be the manifold on the bottom side of the engine. I'm betting this is gonna cost a small fortune ...



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Maybe you have the exhaust manifold broken or cracken check the gaskets too

Posted on Jul 16, 2009


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What is the cause of noisy engine

What kind of noise? Inside an engine there are pretty heavy explosions taking place and they tend to be very noisy, which is why an exhaust system is fitted. The task of this system is to cool down the exploded gases and allow them to lessen their pressure before bringing them in contact with the cooler air outside. If any part of the exhaust system malfunctions, the engine will be noisy.

This system consists of the exhaust manifold, which is bolted directly to the cylinder head and sealed with a manifold gasket, The first exhaust section is usually bolted to this with a flange, which has a gasket or ball and socket seal.

Check the gaskets and check for cracks. After the first exhaust section you will usually find either the second section or the muffler, which allows the gas to expand. Check for cracks or breaks in this unit. From there a further pipe goes to the rear of the car, or in some cases to a resonator box which looks like a second muffler. This has to do with tuning the frequency of the exhaust gases to allow a free flow of exhaust gas at cruising speed to enhance fuel consumption. Check here also for cracks, breaks.

Another kind of noise from the engine could be knocking, which could mean serious engine trouble. If this is the noise you hear, take it to a repair shop immediately.

Sep 27, 2014 | Cars & Trucks

2 Answers

2000 ford focus is very noisy in car when starting in the cold and quiets down as vehicle warms up. Any ideas what could be causing this?

check for broken exhaust pipe or muffler could have hole rusted through muffler or check around exhaust manifold for exhaust leaks.

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1 Answer

2006 gs300 rear rattles

Bet the "mechanic" didn't check the exhaust system hangers.

Jul 25, 2017 | 2003 Lexus Gs 300

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My 2002 jaguar x type 2.1 is slow to pick up speed I've changed the spark plugs the coils the O2 sensor checked for air leaks and it's still the same I've been told it could be the catalytic...

There are many things that could cause that problem but yes the catalytic converter can cause that as well as the muffler or resonator if the car has one. A few ways that you can test that is;
*place a vacuum gage on the intake manifold, start the engine and raise the rpm about 2000 rpm while noticing the engine vacuum. If the engine vacuum starts to drops, the exhaust more than likely has a restriction (could be catylytic converter/muffler/resonator).
* take the exhaust loose before the catalytic converter and drive the car to see if it has power again even though it may be noisy.
If the exhaust system is rusty, there is a good chance that the problem is in the exhaust system. If the exhaust system is not noisy or leaking try puttin your hand over the rear exhaust pipe to stop the exhaust from exiting; there should be a fairly strong push against the hand if the exhaust has no restriction and if it is restricted the push against your hand will be very light or minimum which could indicates an exhaust restriction.

Jan 18, 2013 | Cars & Trucks

2 Answers

How to fix a 1992 honda accord catalytic converter? What does it look like and where is it on the car?

It is located beneath the vehicle and is attached to the exhaust pipe coming from the engine. It resembles a muffler and has your O2 sensor attached to it. It would be located more towards the front of the vehicle versus the muffler which is in the rear.

Sep 26, 2011 | 1992 Honda Accord

1 Answer

The engine sounds very loud as if there were no muffler, therefore I was told I need to replace the "flex pipe". However I think that the problem is something else, possibly with the valvetrain....

The flex pipe is located towards the rear of the engine, under the vehicle. It will be very obvious, you mentioned it was loud as if missing the muffler and coming from the rear of the engine. That sounds like a flex pipe and/or front pipe problem.

Mar 05, 2011 | Hyundai Sonata Cars & Trucks

1 Answer

There is a clunking noise coming from the rear underside of my 2003 Mitsubishi Outlander.It is noisy when changing direction particularly when setting off from cold.It is less prominent when the car has...

You could have a worn rear strut which will need to be replaced. Also check some very minor things such as a loose muffler. And, a major ailment could be an extremely worn axle assembly or worn rear end assembly. Also check for things such as loose spring hangers as any small insignificant seeming part that is loose can cause rackets and odd noises and could run into catastrophic failure.

Jul 10, 2010 | 2003 Mitsubishi Outlander

1 Answer

Engine Trouble

Your getting backfires? hmm interesting. Seems like your engine is getting flooded and either purging it out of the exhaust or burning it all at once or both (backfire). Sounds like a leaky engine valve to me.There again the bluish smoke indicates to me thatyou are leaking oil somewhere- bad rings or head gasket maybe, which could cause a loss of compression which could also cause your problems.That rattling from the left/rear side sounds like a bad muffler try kicking the muffler (not hard though) next time you walk by it.

Mar 10, 2009 | 1993 Nissan Altima

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