Verify blown head gasket - B&S Vanguard

ttx_rooney(South Illinois)November 7, 2009

First of all, thanks to the many members posting to this board. This has been a fantastic site for years.

I could bore you with the details, but I'm reasonably sure the head gaskets in my Briggs model 350447 18hp engine are blown. Was in a hurry and overfilled the crankcase, drove it hard for 90 minutes, then pumped out 8oz to get it down to full. It was spewing smoke, the plugs were almost oil fouled and they were cleaned earlier in the day.

Several people have mentioned removing the valve covers and looking for a vapor leaking. This one will literally spray you, and the engine runs better while the cover is off.

How much leakage is normal? It certainly looks like these are leaking, but I don't have a good one for comparison. Should there be almost zero vapor?

I plan to order the complete gasket kit and overhaul manual.

Thank you!

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mownie(7)

Reading between the lines here, I sense that you you may be leaving out some key details of events (those boring details?) that preceded your overfilling the crankcase. Was the engine already using oil and smoking prior to you over adding oil? Did you possibly run the engine oil low before you overfilled it. If any (or all) of these questions can be answered "yes", your engine could have damage other than a failed head gasket. I feel certain you will remove the heads and you need to roll the pistons to BDC and inspect the cylinder walls for scratches and signs of galling. If you find any damage to the cylinder walls from galling, you will need to have the damage assessed by a competent small engine shop. Otherwise, proceed with the suspicions of a failed head gasket.

    Bookmark   November 7, 2009 at 9:32PM
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ttx_rooney(South Illinois)

Thanks for the reply.

The engine was running flawlessly before it was overfilled. Sounds like spraying oil/vapor is more than likely failed head gaskets. I guess normal operation is little or no leakage?

    Bookmark   November 7, 2009 at 11:33PM
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rcmoser

"Was in a hurry and overfilled the crankcase" that's a 1200 to 1700 dollar engine in your mower, more than a Vintage SBC or SBF. I hope this is an eye opener to others how costly it can be when dealing with oil levels, changes, and properly checking?????? that is why I don't get rid of my 20 year old LT4000, 300 dollar LT with a 1000 dollar engine. I won't give that engine up.

    Bookmark   November 7, 2009 at 11:40PM
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wheely_boy

I once ran a Briggs Vanguard hard after overfilling with oil and the gasket failed in rather spectacular fashion. Loud pop; large plum of smoke. The engine overheats when you do this. I had a similar experience with removing the valve covers; sprays oil all over. I changed the head gasket and it ran flawlessly again.

    Bookmark   November 8, 2009 at 6:39AM
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rcmoser

wheely boy I thought you were smarter than that!!!!!!!!!! hee, hee. Nothing like bringing some skeletons out of the closet! I bet your more observant now when you change or check the oil???

specking of oil changes, if anybody has there oil changed at the quick service stations (jiffy lub, Quacker state ect...) I would check the oil before I leave. Some think every car holes 5 quarts and they are so quick they don't check it. As me how I know this????

    Bookmark   November 8, 2009 at 8:54PM
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ttx_rooney(South Illinois)

Practically zero vapor is the normal condition?

    Bookmark   November 9, 2009 at 9:09AM
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ttx_rooney(South Illinois)

Here's a pic of one cylinder. It was spraying oil, but there's not an obvious break in the gasket. I guess it can be a pin hole breach?

http://s875.photobucket.com/albums/ab316/prooney/

    Bookmark   November 11, 2009 at 6:43PM
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ttx_rooney(South Illinois)

I looked at the gasket closely with a bright light and on the underside on the top right a thin layer could be missing. Was expecting something more dramatic...

    Bookmark   November 11, 2009 at 7:19PM
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mownie(7)

***"underside on the top right a thin layer could be missing"***
Would that be looking at the photo as it is shown here? If so, that would allow compression to leak over into oil drain-back hole (the hole in head where the long straight slot in the gasket is) and thus into the crankcase and valve cover compartment. Was it around this hole in the head where you were observing the mist/vapor?

    Bookmark   November 11, 2009 at 9:50PM
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ttx_rooney(South Illinois)

Mownie,

Your expertise is always appreciated, thanks for the reply. It was difficult to tell exactly where the spray originated, but there was a lot of it. I expected to see more damage near the bottom of the photo because it might have been spewing from that area. I'm cleaning up this one with a skotchbrite pad, etc. tonight and tomorrow. Don't want to disassemble the other cylinder until I have the manual.

    Bookmark   November 11, 2009 at 10:25PM
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mownie(7)

Well, it would be nice if you could offer up a couple more pics of the situation before you get the head and cylinder deck cleaned off. Sometimes there is visual trace evidence on the head or cylinder surfaces to verify a failed head gasket even if the gasket itself appears to be "intact".

    Bookmark   November 11, 2009 at 10:32PM
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ttx_rooney(South Illinois)

Thought I'd follow-up and let everyone know all is well. Just finished blasting around for awhile in the dark on the Cub Cadet 3185 and it runs fine. The big challenge was adjusting the valves, but tons of info on this site from Walt Conner and Mownie help immensely. Many thanks!

    Bookmark   November 19, 2009 at 10:18PM
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junkman108

was it the head gaskets?

    Bookmark   August 1, 2010 at 9:21PM
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