8.1L Flapping / Rattling noise under load

[swreeder70]

I recently purchased a 07 Winnebago Adventurer that has a 8.1L engine with 18,500 miles on it.

I have put about 4800 miles on it since purchase and overall I am pleased with the way it is performing / running.

However when pulling a steep hill or grade that taxes the engine, I notice a loud flapping/rattling sound. You can hear it more from the passenger side than from the drivers side. The engine does not appear to be missing or loosing power and if I back off the throttle, it will go away or disappear. I do not ever run it at WOT and just have been backing off if I notice this occurring.

I've spot checked some plug wires to make sure this is not the infamous frying of the wires and they appear to be in good shape with no noticeable damage. In this coach there is plenty of space around the manifold and plugs so I do not think it is heat related.

This engine also likes to eat oil at a rate of about a quart every 2500 miles.

Any thoughts on what this is, if it is a problem and what I need to look for?

[NALSO]

Have you checked the fan and shroud?
Is the shroud loose, or is there a gab between the shroud and radiator?

As far as the oil consumption, if you change to synthetic oil this will reduce the amount burned/used.

NALSO

[Joe Gilbert]

Some people have reported oil usage this high and higher. If your using 5W-30 I'll be your usage will drop in half if you use 10W-30. Mine uses less than a qt in 5000 miles. I use Mobil 1, 10W30.

JoeG

[swreeder70]

Thanks for the tips.

Fan shrouds and bolts are all tight and look good. I did notice that the wire harness that powers the fans was hanging loosely in front of the fans with lots of play so I zip tied it down. I found a few other wiring harnesses that were also loose and tied them down as well.

I'm just hoping that the sound is not something mechanical, my first thought was a stuck lifter or some kind of valve problem.

As for Oil, doing my first change this weekend and will be going to Mobile 1 in 5W-30.

[Mekanic]

Quote:

Originally Posted by NALSO ........ As far as the oil consumption, if you change to synthetic oil this will reduce the amount burned/used. NALSO

if you switch to a synthetic it will use oil at a faster rate. It flows more easliy into the smaller nooks and crannies and lubes better because of that. 2500 miles per quart isn't all that much of a worry if it were mine.
The noise could be a slight leak at the exh manifold and like the other have said look at the fan schroud to see if the fan is hitting it.

[Tom-NC]

HI,

Did you check the mud flap under the passenger side behind the wheel, is it loose?

If there is a howling sound that would be the fan clutch engaging.

I have an 8.1 liter and haven't noticed that noise. Also check air cleaner housing.

Good Luck!

[jfran304]

Check the donut gasket between the exhaust pipe and exhaust manifold. They have a history of going bad due to the flange not being tightened.

I also recommend using Mobil 1 10x30 full synthetic oil.

Jon

[JimM68]

1. Exhaust leak.
2. spark knock (pinging)

[Midniteoyl]

Quote:

Originally Posted by JimM68 1. Exhaust leak. 2. spark knock (pinging)

Agree...

Would like to see the exhaust temp/color...

[hamguy]

Quote:

Originally Posted by jfran304 Check the donut gasket between the exhaust pipe and exhaust manifold. They have a history of going bad due to the flange not being tightened. I also recommend using Mobil 1 10x30 full synthetic oil. Jon

I had to replace the 'donut' gaskets at 64,000 miles.

As to oil consumption, I have 85,000 miles now and use about 1qt/3k miles on flat lands and 1 qt/1k miles in mountains. Not unhappy at all.

[Fred and Bonnie]

Possibly bad cat. convertor, then they go bad all h**l rattlets around.

fred

[swreeder70]

Quote:

Originally Posted by hamguy I had to replace the 'donut' gaskets at 64,000 miles.

So anything to look for on the gaskets? I cannot see any visible carbon or soot around the manifold, all bolts from what I can see seem tight.

[JimM68]

Pull the plugs... Look at em under a magnifying glass. They should be tan to white, but not pure white. Look at the porcalean (sp) insulator around the center electrode.
silver flakes = pinging = bad.

If you have an exhaust leak, there will be telltale marks.

[DriVer]

Quote:

Originally Posted by swreeder70 This engine also likes to eat oil at a rate of about a quart every 2500 miles.

1 quart every 2500 miles is outstanding. The guidance from GM is for 1 quart of oil every 100 gallons of fuel burned as being normal. (we have had heated debates about this but they made the rule). Your consumption is about 300% over what can be considered normal according to GM. I wouldn't worry about it.