GM 6.2 DIESEL INTAKE BUILD UP 1

[JTM]

I HAVE A 6.2 DIESEL AND THERE IS A BUILD UP IN THE INTAKE UNDER THE AIR CLEANER.
IT IS A OILY SOFT BUILD UP ON THE INTAKE SIDE IT CLEANED OUT EASY BUT I WONDERED
WHAT WOULD CAUSE IT AND IS THERE A WAY TO PREVENT IT. ANY SUGGESTIONS WOULD BE APPRECIATED.

THANK YOU
JOE MILLER
JTM@WILLARD-OH.COM

 

[mattsooty]

Jim

You don't say what sort of build up there is!!! If it is a wet, black coloured, oily spot then what follows may help...

Is the build up near a crankcase 'breather' hose outlet??? If it is then this may mean that there is positive pressure in the crankcase. This can be caused by:

1) the cylinder bores/piston compression rings starting to wear allowing combustion gases past them and into the crankcase. These gases obviously want to go somewhere and out of the breather hoses is usually the first place!!!

2) I am not familiar with the engine that you mention, is it turbo'ed? If it is then there may well be a breather hose outlet fitted to the inlet manifold (post compressor). This is designed to work only when there is negative pressure in the manifold. It will therefore have a built in valve that closes when positive pressure is experienced within the manifold (ie on boost). These valves can and (often) do stick open, the result is when your turbo is providing boost there is not only positivie pressure in the manifold but also in the crankcase!!!

Ways to tell if the crankcase is being pressurised:
1) Check around the dipstick tube, quite often oil will be forced out and can be found running down the tube after a hard run.
2) Oil seeping out of any part of the crankcase, gaskets and often past the crankshaft seals (front pulley end and gearbox end, both bad news) check these out!
3) You may notice that 'burnt lube oil' colour in the exhaust gases. This is due to oil being forced past the scraper and compression rings by combustion gases in the crankcase.
4) Oil consumption may well be up because of the above.


My recommendations:
1) Give the whole breather system a clean out and see if the problem continues.
2) If it does, clean up again and then try clamping the hose to the manifold (only if running a forced induction system, see above)
3) Check the state of the bores/rings. My first test would have to be a wet/dry compression check on all pots. If that is OK, it maybe worth borescoping the thing. These tests will tell you quite quickly and easily the state of the bores/rings. If you find that the rings/bores are worn, sell the thing ASAP (unless you want to overhaul the engine). Blown crank seals etc can be expensive (read pain in the arse if doing the work yourself).


Matt

 

[95yukon]

Jim,
I've owned a 6.2 and now have a 6.5. The engines have what is called a CDR (Crankcase Depression Regulator) on the passenger side valve cover. If you have a lot of miles it may need replacement, they are designed to keep a negative pressure in the engine crankcase but also to help burn blowby.

Depending on the miles of the engine you may also have some blowby from valve guides, however I wouldn't get too concerned unless you are having problems with burning oil. I sold my 6.2 at 205,000 miles and it was still running strong and not burning oil - it got 23 mpg on highway trips.

This engine also can be equipped with an EGR valve that can really mess up your intake, but is required most places. It is usually only on 1/2 ton trucks - the heavier ones usually don't have EGR. I plugged the vacuum hose to mine as it caused driveability problems and more black exhaust smoke than you could imagine.

One final place you can go it to a club that I've joined. Here is the website:

http://www.thedieselpage.com

There is more info here than you will ever imagine for the 6.2 and 6.5 diesels. Many members are engineers - I was a diesel mechanic for 15 years before becoming an ME. Jim Bigley is the one who started the club and runs it - he's from Montana, and usually has a yearly rendezvous.

Hope this helps.

Dave