jrv15

i have a 99 24 valve dually 118,000 miles i have had it for ten thousand miles. when i first bought i changed the oil to mobile 1 5w30 extended performance synthtic. well after about a month i started to notice a lot of smoke coming from under the truck when sitting at a light. after investigating this i noticed taht all of it was coming form what looks like th blow by tube. i took it to a diesel mechanic form guy motors in charlotte hall MD. his first response is that i have severe blow by and the engine is going to go pretty soon. when i told him what oil i use he said that he is 90% sure that the oil was the problem. he sold me amsoil 15w40 with an amsoil filter and said that should clear it up. i changed the oil. smoke hasnt changed, but its only been a few days. any help would be great. i didn see a couple other threads saying something about the heater. well when i turn my heater on it only comes out of the defrost windshield vent no matter what switch i have it on. DOES THIS SOUND LIKE A BAD ENGINE??? A CUMMINS WITH ONLY 118K this engine is barely broken in so they say!!!!

estrada5.9

Most likely not a big deal all engines are going to have some blow by at idle not a lot of combustion pressure sealing the rings against the cylinder wall so so of the combustion gas goes past into the crankcase and out the blow by tube.

Use can have the compression checked for a warm fuzzy but if it runs good gets good mileage doesn't blue smoke and burn oil yer probably good to go.

Silver R/T

ya, that was wrong oil to use on Cummins. Not sure if it did any damage to engine or not.

torquefan

On these engines, the vacuum pump vents into the crankcase. So, if you get a vacuum leak anywhere in the system it pumps a bunch of air into the crankcase which ends up exiting through the breather tube. If your HVAC is stuck on defrost it tells me this is probably your problem. You need to check the whole system for vacuum leaks.

Vacuum runs your HVAC directional controls, 4WD front axle disconnect, and cruise control (if equipped). Firstly you need to check your vacuum pump output. Remove the main vacuum feed hose from the pump and measure your vacuum at the pump at idle with a vacuum gauge. It should be 18 inches of vacuum or more. Remember that number. Now, reconnect the vacuum system, then TEE into it somewhere (at the pump, or up at the firewall) with the gauge. Read vacuum at idle. If the value is now much less with the whole vacuum system connected, you have a leak. You can disconnect and plug off each branch of the circuit, one-by-one to isolate your leak.

Hope this helps.

Thundercraft

I think torquefan is onto something here. I agree that the HVAC is a big part of the clue.

There are lots of guys who run 5w-30 in these engines, even in California so I doubt that any damage was done by running that oil.

nickg

so long the oil is diesel rated it wont matter what the weight is.
as for blow by, its normal to have "smoke" vent out, most times its NOT blow by, as the crankcase ventilation system on the cummins is not a postive crankcase ventalation, its a road draft tube, so all air in the crank case is "moved" or pushed out the blowby tube because of the air being pushed around by the moving pistons, it becomes blowby when compression gasses leak past the rings or there is a hole in a piston, usually if there is a ring problem you will have other issues like hard starting and excessive smoke(white) out the tail pipe

dont sweat seeing a little "steam" blowing out the tube, I doubt you have a blowby issue.

post a video if you think its excessive, then we can see better and give a better diagnoise

Dinner

Why is it the wrong oil? Look up in your manual, Cummins Repair Manual, etc and 5W-40 is rated for cold temps to hot temps. There is nothing wrong with running 5W-40

dozer12216

Reread and perform test promoted by torquefan. He has your problem nailed. Blocking the vacuum hose at pump should give immediate results..........................
5-30 oil not harmful, but not what is normally used unless in Alaska or Canada. 5-40 syn oils are highly recomended for virtually all climates. Quality 15-40 dino oil is more than adequate for vehicle also.

gmanw9

I have a 2001 Dodge 24 Valve that had the same problem. A/C blowing out the defrost vents at idle, Excessive smoke/oil coming out the vent tube. I thought for sure my engine was toast. Two local mechanics even said so. Quoted me in the neighborhood of $10k for a reman engine.

Took a look at my vacuum hoses. All the rubber sections were rotted and cracked. Replaced these at a cost of about $6, and no more issues. No blow by that I can detect, and A/C controls now work properly.

Mike L

WOW! you went from a >$10,000.00 repair to a $6.00 fix? Man, you better buy Torquefan a big 'ol beer for that save!

Cheers boys and girls! Carry On!

Mike

SIXSLUG

Mine was also blowing what seemed like a lot of oil out the blow by. Replaced the vac line plug on the splitter at top rear of engine on firewall...problem solved.

Any Cummins rated oil will perform in your engine. Suggested weight range is 15w-40. Mobil is a good oil. So's amsoil. I avoid all the hype and run plian old 15w-40 from Shell, Mobil, or Valvoline...whatever is on sale....

KATOOM

Its amazing what you hear come from the mouth of professional mechanics..... This is why I ALWAYS highly suggest that if you're going to have a mechanic touch your vehicle then make absolute sure that they are proficient in the vehicle you're wanting to work on. I was a mechanic before realizing that working on grandma's Cadillac wasn't what I wanted to do forever and just because someone works on cars does NOT mean they know anything other than how to turn a wrench.

As for the blowby, clearly torquefan's diagnosis is right on the money. This is a vacuum pump leaking and blowing all that air in the crankcase and keeping your vent selector from working. But that said, these engines are open loop and do vent their crankcase vapors directly into the atmosphere, so you will always see some air coming from the blowby catch bottle. The correct amount of blowby would be compared to about how forceful you could blow air out a 3/4" hose with your mouth. Also, after changing the oil you may notice more blowby stink, especially with certain oils. The 5-30 Mobile is fine and didnt hurt anything other than your pocket book. Same goes for the Amsoil. Although 5-30 is too light unless its really cold out.

I wont turn this into an "oil thread" but if you do a simple thread search about oil's and what to use, you'll quickly see that its all personal preference and those threads tend to turn into a heated and argumentative discussion. So the only things I'll say about oil is DO NOT use Fram filters. Other than that.....

torquefan

Glad I could help! Six bucks is my kind of repair bill.

Tallguy67

I don't want to hijack this thread but all of the explanation of the vacuum system got me off my backside today and I fixed a problem with a small screw out of my spare parts bin. A couple of months ago I had my transmission rebuilt. Ever since then my cruise control has been really sluggish. Then last week we had our first day that was warm enough for me to use the A/C. I immediately noticed that the air would only blow through the defroster vents. Ok, now I know what is going on, I have a vacuum leak. Following the explanations above I found my leak in less than 5 minutes. It turns out the guy that worked on my tranny noticed that I have a manual CAD instead of the stock vacuum one so he removed the vacuum line that goes from the T on the firewall to the transfer case, but he didn't plug the hole in the T. I put a small screw into the hole and now my A/C blows in my face again and the cruise control is immediately responsive. Thanks Torquefan and Katoom for the help.

KATOOM

Its always nice to know that these threads can bring more than anguish and anxiety.....