| [GMCnet] High oil consumption maybe solved [message #250066] |
Sun, 18 May 2014 18:19  |
glwgmc
Messages: 1014
Registered: June 2004
Karma:
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Senior Member |
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A while back I posted about the seemingly high oil use in the Clasco, about a quart every 200 to 300 miles. I checked all the normal suspects (dip stick calibration, PCV system, leaky pan gasket, leaky valve cover gaskets, oil cooler lines and fittings, etc.) and also found the plugs were all a nice chocolate brown so that tended to rule out internal things like valve guides or worn rings, etc. Finally, I added a bottle of dye to the oil and drove it until a quart had gone somewhere and took it to a mechanic with an oil change pit. Using a black light and the special goggles he could see oil coming down the front of the engine from the area where the intake manifold gasket runs across the "china wall" (the thin casting at the front of the valley between the two cylinder banks). This is a 77 coach and originally had the rubber surround around the radiator fan. That configuration required a couple of large brackets bolted to the front side of the engine to support it. I r
emoved that mess last year and put in one of the split type fan shrouds that make it much easier to change out the fan clutch, but I left two of those vestigial brackets in place as they were a bit hard to get to and I was lazy at the time. With those brackets in place it was hard to see the front of the engine clearly so I removed them and could see the culprit. A large piece of the rubber gasket that was supposed to seal the china wall to the intake manifold had pouched out leaving a significant gap where oil fumes from the valley area or even liquid oil in that region could find their way out. The fan would pick up the oil and move it back across the hot manifolds where it evaporated as we drove. Hence, we did not see heavy leakage onto the ground and did not see blue smoke from the tail pipe, but a lot of oil came out of that gap.
Today I had the mechanic come over and remove the intake manifold (too heavy and awkward for these old bones). Close examination failed to show any cracking at all either along the bottom of the cross over area (the cross over had never been blocked) or along the wall between the secondary bores. So, it was heavy cleaning time on the manifold. The original turkey tray was caked both sides with burned oil residue but the valley was quite clean. From inspection of the turkey tray area around a couple of the intake ports it looks like there may have been some leakage there as well but it did not show up on those plugs. We carefully cleaned the heads, vacuumed out the valley floor and the ports in the intake manifold and put it all back together with Great Stuff RTV and the block off plate gasket set from Jim K. We did not use the rubber pieces along the china wall but instead used a good bead of the Great Stuff. Everything appeared to seal correctly and hopefully that wil
l be the end of the high oil use. We are headed for the Cascader ralley at Pheasant Ridge RV Resort in Wilsonville, just south of Portland, this next week (about a 600 mile round trip). All the gang that will be doing the Route 66 Rally will be there as their official kickoff. Should be fun. I will keep you posted as to whether replacing the intake manifold gasket solves the issue or not. Hope so.
Jerry
Jerry Work
The Dovetail Joint
Fine furniture designed and hand crafted in the 1907 former Masonic Temple building in historic Kerby, OR
Visitors always welcome!
glwork@mac.com
http://jerrywork.com
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Jerry & Sharon Work
78 Royale
Kerby, OR
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