Excessive Engine Smoke

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Excessive Engine Smoke

May 22, 2013, 12:26:48 am

New to Forum ... Greetings ..... I just purchased 1997 U295 with CAT 3126. Coach has not been driven for about 3 years. Engine full serviced within last month. Runs nice and smooth, all temps and guages normal. PROBLEM ..... when I first start the engine, there is A LOT of gray smoke that appears to billow from the hose that hangs down under coach. On highway, it seems to blow quite a bit of black smoke under load. Drove it today for 2 hour trip. As I was allowing engine to cool down at idle speed, engine again was smoking (gray) excessively. I don't know how long diesel fuel was in tank, I have put about 1/2 tank of new diesel in tank, and put in a quart of Mystery oil from walmart into gas tank and oil crankcase. I have only driven coach about 8 hours since serviced. I've been told it just needs to be driven.

Any advice or thoughts are appreciated!

Re: Excessive Engine Smoke

Reply #1 – May 22, 2013, 09:18:24 am

How many miles on the engine? I'd have a CAT repair shop check out the engine before I drove it. You didn't have it checked out before the purchase? Why did you add the Marvel?

Re: Excessive Engine Smoke

Reply #2 – May 22, 2013, 10:01:24 am

Engine has right at 90k miles. Actually it was inspected by two different shops. The 1st shop did a complete engine and generator service. I drove it from there to a large RV shop in Knoxville, and paid $1,000.00 for a "Complete" inspection of the entire RV (10hrs of inspection). I drove it back 2 hours to a tire shop. During the 1st 6 hours of travel it did not smoke. When I picked it up from tire store to drive 2 hours back to knoxville for repairs found from their inspection, was the 1st time it blew the gray smoke at start up, and at idle. On the highway it doesn't smoke. The mechanic advised me to put a quart of the mystery oil in the oil fill up. I've been told it sounds like the injector pump could be bad or clogged.

Re: Excessive Engine Smoke

Reply #3 – May 22, 2013, 11:01:13 am

Jayncat,. Start with the simple things. Clogged air filter will show BLACK smoke. Change fuel filters. On some engines blue smoke on cold start is ALMOST normal. On hard Pull may see black smoke. Smoke from slobber tube is not normal, may smoke some but hardly visible. Cold engine from open thermostat will sometimes cause blue smoke, is engine coming up to temp ? Water in fuel would cause blue smoke.Three years of non use may contribute, using injector cleaner Will not hurt and may help.
If it continues for more than a few more miles the CAT Shop should look at it.
Go to the CAT owners website, should be a lot of info there.
Good Luck
Gary B

Re: Excessive Engine Smoke

Reply #4 – May 22, 2013, 11:07:26 am

Quote from: Gary Bouland – May 22, 2013, 11:01:13 am

If it continues for more than a few more miles the CAT Shop should look at it.
Go to the CAT owners website, should be a lot of info there.

CAT forum link (now known as Diesel RV Club forum) Diesel RV Club, an FMCA Chapter As Gary suggests, there's a lot of engine expertise over there that can help. Brett Wolfe (moderator here) is their Technical VP so you know they're a helpful group.

Re: Excessive Engine Smoke

Reply #5 – May 22, 2013, 11:10:42 am

A 3126? Sure that's not a 3176? I never knew Foretravel put the 7.2L 300hp 3126 in the Unicoach. I know the 3176 was sold in both 320s and 295s, especially 95 and 96 - normally special order for Cat lovers...

Re: Excessive Engine Smoke

Reply #6 – May 22, 2013, 11:16:44 am

Jayncat,

Couple of questions. Have you owned a diesel before? How much black smoke on the freeway? On cold startup, does it pulse out the white smoke and run smoothly or run rough for several seconds before smoothing out?

Injectors do get dirty and 3 year old fuel will be out of spec but probably only show up on a emissions test. Marvel Mystery Oil is not one of the recommended additives if you have a leaking injector. Here is a list of additives and an article to go with it: Lubricity Additive Study Results - Diesel Place : Chevrolet and GMC Diesel Truck A "mechanic" that recommends Marvel and then says the pump may be bad or clogged may not be the guy you're looking for.

White smoke on startup can caused for several reasons. The injector may leak after the engine has been turned off and pool a small amount of diesel on top of the piston. This shows up as white smoke for a few seconds, more if the weather is cold. The injector may be dirty and the spray pattern poor. This may mean that the cylinder with the dirty injector takes a bit longer to start relative to the other 5 cylinders. More serious problems could be low compression in that cylinder but you have a very low mileage engine so not likely. You can spend a lot of money getting the engine checked out with a company more interested in your pocketbook.

A very small amount of black smoke going down the freeway is normal. It may increase on hills and not be visible downgrade.

I have seen on several forums that older pre ULSD (ultra low sulfur diesel) may not get as much lubrication from the fuel as the factory intended to the injection pump and many will add petroleum (non-synthetic) 2 stroke oil to the diesel fuel at a 1:200 ratio. Mercedes has done this in certification driving in other countries rather than importing their own fuel.

Our 6V-92TA Detroit takes a couple of seconds to pickup the last cylinder when cold starting and in cold weather and will belch out vast clouds of white smoke in freezing weather. I know it needs a new injector but too busy to fit it. Easy way to tell is to wait until the engine just starts to smooth out, shut it down and then feel each port on the exhaust manifold. The cylinder that starts last will have a much cooler feel on the manifold.

Pierce

Re: Excessive Engine Smoke

Reply #7 – May 22, 2013, 11:23:11 am

To me it now sounds like some piston ring blow-by at idle do to stuck piston rings. Adding Marvel oil To the fuel and crankcase may clear it up.It can be a problem for any engine that hasn't been run for that long a time ,and wasn't laid up correctly to begin with. Gam

Re: Excessive Engine Smoke

Reply #8 – May 22, 2013, 11:38:14 am

My GUESS would also include the lack of a good hose between The turbo and intake, low boost pressure sure will give you max black smoke for example. Blow by will not normally give BLACK smoke.

Re: Excessive Engine Smoke

Reply #9 – May 22, 2013, 12:07:02 pm

I think Jayncat said On the road it doesn't blow black smoke any more and at idle the gray smoke is coming from the crank case vent hose .He also said that he had a complete engine service [ filters and oil change? ]. Gam

Re: Excessive Engine Smoke

Reply #10 – May 22, 2013, 01:05:50 pm

Not sure where I picked up on the black smoke, but finding it is a Caterpillar, it sounds normal to me. I am not a Cat fan, so FWIW
Dave M

Re: Excessive Engine Smoke

Reply #11 – May 22, 2013, 04:41:30 pm

First, yes, Foretravel did use a limited number of Caterpillar 3126's-- I have seen three, all 1997's.

Since the smoke is coming out the blowby hose, two observations-- one inexpensive, the other expensive:

1. Crankcase is overfilled with oil and is puking it out. Call the Caterpillar RV Hotline with your engine serial number to determine the correct quantity of oil: 877 777-3126. Then make sure it is not overfilled. Do not assume that the engine oil dipstick is exactly accurate-- calibrate it.

2. Ring(s) are seized/damaged by sitting. Requires hot end overhaul.

Were it injectors, etc, the smoke would be coming out the exhaust, not blowby tube.

Re: Excessive Engine Smoke

Reply #12 – May 22, 2013, 06:13:12 pm

I'm betting on the over filled oil since it was recently serviced.

Re: Excessive Engine Smoke

Reply #13 – May 22, 2013, 11:16:46 pm

Thank You all for your thoughts and comments!!! I appreciate them.

This is my second diesel pusher. My 1st was a Fleetwood Discovery. It actually blew more black smoke when accelerating than this one.

The mechanic in Knoxville told me he too thought my engine was the 3176. I have a Foretravel Owner's manual that lists the U295 as having the 3126. My coach is a 40ft if that helps. I will call the cat hotline to find out for sure.

I had a diesel mechanic of 30 years tell me today if the blowby hose is not blowing oil, it is safe to drive, and could be an injector if one is leaking under the valve cover. He said most rings that do stick, do NOT become unstuck. He also told me to take off the oil filler cap, and see if there is moisture there after sitting overnight, if so condensation is apparent, and could take quite awhile to get rid of. He told me of an additive called polybutylene to put into the oil to soak up the water.

The mechanic in Knoxville advises me to keep putting in the additive and drive it. I will read the articles about these other additives and probably try them. I have not yet actually checked the oil level. I thought after having 2 PDIs that one of the 2 professionals would have made sure all was done correctly.

If the rings are stuck, won't driving it make matters worse?

Thanks Again

Re: Excessive Engine Smoke

Reply #14 – May 22, 2013, 11:25:33 pm

My Cummins smokes (black) on heavy acceleration. I have a 93 mechanical engine. The mechanic at the Cummins dealer in Sarborough Maine told me it was because I had a mechanical engine and it takes a bit of time for the turbo to spool up and catch up to the fuel feed ergo the black smoke. It does not smoke at all on start up or when we are cruising down the road.

Roland

Re: Excessive Engine Smoke

Reply #15 – May 23, 2013, 12:09:58 am

Not that this is your issue but I'm told that turning up the engines power by adding more fuel if overdone can wash down the cylinder walls with diesel fuel which is two weight kerosene or something like that versus the engines actual oil supply. That can damage rings and lose compression. Grey smoke results.

Re: Excessive Engine Smoke

Reply #16 – May 23, 2013, 08:38:00 am

Yes, if the rings are sticking, driving will make it worse. Remember, the 3126 is a parent bore engine, not sleeved engine, so scoring the cylinder walls can add to the repair bill. There are well respected outside companies (not Caterpillar) who bore and insert a sleeve in a damaged cylinder.

I know Mustang Caterpillar in Houston uses their services, as I have seen the outside company doing this in the Mustang shop.

Brett

Re: Excessive Engine Smoke

Reply #17 – May 23, 2013, 10:29:32 am

Jayncat,

Would not leap to conclusions that sticking rings are the problem but they certainly could be. Your mechanic is correct in that taking off the oil filler cap while the engine is running will tell a lot about the compression ring(s) condition. Some blow by is normal but you should have the mechanic take a look at the amount as he should be able to tell in a glance if there is a problem. I have started a couple of CATs (bulldozers) that sat for 25 years and they ran fine. Usually, if a ring is sticking, it will remain stuck and time won't free it up. I have freed up a gas engine by filling the combustion chamber with liquid wrench and letting it sit for a couple of days. You need some professional on site advice. Forum opinions are just that.

I think (but certainly not sure) that a Detroit 6V-92TA is the only Foretravel engine that can be overhauled "in frame", in other words, without taking the engine out. If you look at the rear of your rig, you can see that unless you have a very late GV, the rear cap is one piece and removing the engine will take a more time and equipment and at $100 plus per hour... Get a mechanic to check it out before hitting the panic button.

Pierce

Re: Excessive Engine Smoke

Reply #18 – May 23, 2013, 11:20:32 am

A good read about to much oil and blow by for the cat 3126. try ,how much oil is enough discovery owners association forum, looks like cat dropped the oil level to 19 quarts with some oil pans.Gam

Re: Excessive Engine Smoke

Reply #19 – May 23, 2013, 11:31:56 am

I would think a compression test could also be done if the blow by evaluation is inconclusive.

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