Hi,

I just replaced the 3 rear platinum plugs on a Magna 2004 TL and have noticed quite a drastic sound change when I accelerate. It sounds more 'throaty' plus there's a slight rattling sound coming from under the bonnet. The rattling can't be good :eek2:

Before I head in there and look around I thought I would ask on here if anyone had experienced the same thing after changing plugs and knew of any possible causes?

The intake manifold plenum wasn't a total nightmare to get off and the only thing I replaced was two gaskets as I already purchased a gasket kit in case it was needed. I highlighted them both in green in the image.

http://i1283.photobucket.com/albums/a548/conanthedestroya222/plenum_zps1d10721d.jpg

The tube seals looked fine and there wasn't oil down on the plugs so left the seals in place and everything else was tightened up to the Nm value as shown in the same image.

I made sure that the gasket was correctly in place on the air intake section (highlighted in red in the image) although I must admit the top left bolt was a real pig to get back in as there was quite a bit of moving around to get the bold started in the thread. The other 3 bolts went in easily. Looking at it though it all looks sealed as before I started the job.

I was actually quite chuffed as this is my first 'hands in the engine' diy job and the labor cost I saved I got myself good Stanley toolkit plus a Kincrome 3/8In Drive Torque Wrench. Not much good though if I've destroyed something important.

Any help is appreciated.

Thanks,

Andrew

What kind of rattle is it? Metallic? Dull? High/low pitched? Frequency? Does it increase with revs? etc.

When I did my rear plugs. seals and rocker gasket, I found that the smaller gasket on the exhaust recirculation connection on the rear of the manifold can drop out easily when you feed the bolts in, so it ends up on the ground or on the steering rack when you think it is in correctly. lol Worth a look, perhaps?
Also worth checking the rear manifold stays are attached correctly.

Hi,

Hard to describe it in a post so recorded it. I couldn't upload the mp3 file so just added it to the following webpage.

ENGINE SOUND (http://www.cicadastudio.com/index.php?option=com_content&view=article&id=98)


That's the sound of the engine ticking over with the metallic sound ticking away. When the car is in gear and out the the road it kind of sounds like something metallic touching a fan blade as the fan spins around. The more revs applied the faster the repetition. I only heard this since I removed the manifold plenum so presume it's something I've done.


MadMax
I found that the smaller gasket on the exhaust recirculation connection on the rear of the manifold can drop out easily when you feed the bolts in

Is that the one at the back that I highlighted in green that takes two bolts? If so I did have a problem with that as it dropped while I was trying to get the two bolts back in place and disappeared into the engine depths out of sight. Thankfully I had a spare in the gasket kit so used that and after reversing the car the original one dropped to the ground. Thank god it did as I would have though that part was causing the metallic sound if still in there somewhere.

Hope that helps.

Thanks,

Andrew

Is that the one at the back that I highlighted in green that takes two bolts? If so I did have a problem with that as it dropped while I was trying to get the two bolts back in place and disappeared into the engine depths out of sight. Thankfully I had a spare in the gasket kit so used that and after reversing the car the original one dropped to the ground.

Yep, that one. I did pretty much the same. lol

I just changed the sound file on the link in my post above. Now you can hear the ticking sound getting louder as the car accelerates and it's definitely coming from the intake manifold plenum area.

All I can think of doing is to take it all off again at the weekend and put it back on and see what it sounds like. Perhaps I should put the old gasket back on? The first attempt took 3 hours but I reckon I can half that no problem now I know what comes off plus hopefully won't be wasting time looking around for fallen gaskets :woot:

Was hoping someone here may have already experience the same sound and perhaps narrow down a solution.

Thanks anyway.

Andrew

The sound seems to match the revs, and occurs with regularity (as you said like a stick in a fan blade)
Given you have just played with spark plugs and leads, it may be that you have a spark lead earthing somewhere.
This would produce a sound that occurs with regularity through the rev range, and account for the sound being newly arrived.
This is just my thought however, as Im just trying to piece it together to help...

Did you retrieve the gasket you lost?

Thanks for the replies.

I never even thought of a spark lead earthing although I'm new to all this. If I have to open it up again I'll check the leads and make sure they look ok. I must admit the rear right side plug (looking at the engine from front of car) was a pig to get off as the lead was so short. It's easy to pull the cap off but then the tube is attached going down inside to the spark plug so there was a bit of moving and perhaps stretching to get it out.

Just checked and it's 20% off (now $72.00) Bosch Ignition Lead Kit - B6158I at SCA so probably good time to replace them anyway while it's all off again.

Yes I got the dropped gasket out. No idea where it went but after starting up and reversing it dropped to the ground. There was a hell of a lot of foul language when when it dropped into the depths though :rant:

Cheers

jdisnow,

You got it right about the spark plug leads. I was going to wait until tomorrow to attack the car but have no patience so started 3 hours ago.

Spent most of the time trying to get out the old leads, especially the back three as they had a real pig of a route down to the cap. Also at one point I mixed up two but thankfully had the manual so so looked it up.

Made a new route for the back three so I don't arse around again, sealed everything up and it sounds great after a quick drive.

One thing I did notice was that after testing each old lead as I took it out with a meter the measurement was approx 5.5 - 6.5 ohms. The new leads all measured approx 3.5 - 4.5 ohms so I'm thinking that's good.

Thanks again,

Andrew