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DIRKPASTOOR

Replacing Air Intake 0n Diesel Engine

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I had to replace the Cat engine this spring and noticed that the fresh air intake going to the air filter is about 15 feet long. It comes off the top of the roof in the rear, I would like to shorten this considerably and make a new intake on the driver's side of the coach, behind the rear tires,and then go thru a compartment to the air filter. Has anybody done this? what precaution do I need to take? how big should the intake be? it supplies a 6 inch air line. Anything would be appreciated. Can't afford to replace the engine again.

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Why was the engine replaced???

Look at the side of your coach after driving in rain. You will see a dirt "pattern" behind the rear wheels. Be sure if you relocate the intake to be ABOVE the dirt line.

But, let's back up a step. What are your air filter minder readings-- that will help you decide if you have restricted air flow. And, before lowering the intake into a dirtier area, I would look at a larger filter housing/filter to lower restriction.

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I hope you mean well above the level of the rear tires. The tires kick up alot of dirt, even on paved roads, but much more dirt on gravel or dirt roads.

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Hi Brett,

Apparently the air intake tubing broke and the turbo sucked a lot of dirt into the engine. Cat's report was that the cylinders were 'dusted'. On the Cat 3126 engine, they did not use cylinder sleeves. I did get 3 independent analysis on this engine. You may remember way back this spring, I reported an excessive smoking problem and this was the final outcome. Instead of replacing the 'short block' we decided to go for the works and replace. Because of the failure of the air intake tubing and it being 15 feet long and hidden for 8 feet, I would rather shorten the intake hose and have it all open for inspection. The MH is not driven on gravel roads as a rule, but some park access is on non-paved roads. The filter is replaced every year and the filter minder is observed faithfully. The present air intake has all been replaced in its old location from the top of the coach at the rear and then for 7 feet along the bottom of the coach and all behind the duallies. I would like to put in a new air intake just below the floor level and close to the air filter and as close to the rear wheels as I can find access. I could put a air scope ahead of the tires and underneath the coach but I think that would suck up to much dirt and chemicals in the winter time. The big thing is that I want to be able to inspect the whole line.

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Dirk,

A break in the intake from top of coach to air filter will NOT dust the engine. The air filter would still filter out any contaminants.

You must have had a break between the air filter and the turbo (if after the turbo, you would have lost a LOT of HP).

Moving the intake lower and on the side will likely result in MORE dirt into the filter.

Brett

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Wolfe 10 is absolutely right any break in the duct going to the filter would have nothing to do with “dusting”. The only possible thing would be hot air from the engine compartment being drawn into the air supply. I would like to hear Cat explain where the dust came from. Do you have the air filter that was installed at the time this happened? Have you checked the tubing to the turbo? I hope you can find out where the dirt was getting in as it may do the same thing to the new motor.

Bill

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Brett,

I wish you were much closer. It would have saved me much headache and skinned knuckles. I replaced the whole line at the suggestion of the Cat service center. They blamed the problem on a broken intake line. They offered to replace it for me at $100/hour plus parts. Hence me replacing it. It needed to be done at any rate as the section under the coach was rotten and had been repaired by somebody who used a back support girdle and much duct tape. The mechanic did say that he had found water in the turbo line and was wondering where it had come from. If the air line to the turbo had failed then it could have sucked up moisture this past winter on our excursion thru the southern US and back to Western Canada. It sounds to me that you almost have to be a mechanic and do all your own stuff as you can not always believe what the shops tell you. There was virtually no loss in power, except at the very end when it started to smoke heavily (was picked up by the highway patrol as they thought I was on fire) and then it seemed to down shift much more then normal. I think I will forget about changing the air intake to a new location. Thanks for your comments and help Brett. It is much appreciated.

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Suggest that you use engine oil analysis to check on the condition of your engine long before it got to the problem stage. I use Wear Check USA, each sample cost about $12.00 and would have picked up your leaking intake and shown it as silicone abnormal.

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I too would like to know where the water came from. Was it found when they were replacing the engine? There is a great suction on the air intake and it could have picked up moisture but it would turn into steam the moment it got to the turbo if I understand a turbo.

Brett, does the term "Dusting" mean the same as glazing of the cylinder walls? I have heard of very small leaks after the filter causing the glazing in dusty conditions.

Herman

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Herman,

Dusting is literally the introduction of dirt particles into the engine through the intake. It is an abrasive and wears out the engine-- most moving parts. The amount of damage is related to how much dirt, what kind of dirt and how far it is run with dirt in it.

Think of it as sandpaper on all moving parts.

Water can do several different things to damage an engine:

Weaken the air filter media, making a breakdown and subsequent ingestion of dirt (i.e. dusting) more likely.

If ingested in sufficient quantity can cause hydrolock. Water is non compressible. When a cylinder fills with water, as the piston comes up, instead of compressing air tries to compress water. The result is that catastrophic damage occurs-- the rod bends, often going through the side of the block.

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