Engine keeps running on, or dieseling - Seafoam fix?

[Radec Aksarben]

My M runs chugging and coughing forever when it's turned off. It has to be killed in gear to shut down. I think this is from carbon build up over time. The problem got much worse when I replace the thermostat that was stuck open - so the engine was running cold for a long time, probably building up all kinds of gunk. Now since the engine is running hotter, hot carbon build up is detonating.

So, has anybody tried using seafoam to fix carbon build up? I plan on spraying about half a can into the carb when its running about half throttle and see what happens. I'll probably dump a can in the gas tank after that and one or two in the crank case for the winter before I change oil in the spring.

[danovercash]

Be careful thinning that crankcase oil!

[Radec Aksarben]

Be careful thinning that crankcase oil!

I've been poking around the internet for a while and it seems that if you follow the instructions on the bottle, 1.5 oz per quart oil, you can run the engine with no ill effect. In cars, it claims you can run it until the oil turns black because of all the freed up gunk, or 3000 miles. Seafoam seems like one of the few snake oils that people believe in.

But I came here for opinions/stories and thanks for yours! Do you know of anyone hurting an engine with seafoam?

[dgrapes59]

Be careful thinning that crankcase oil!

I've been poking around the internet for a while and it seems that if you follow the instructions on the bottle, 1.5 oz per quart oil, you can run the engine with no ill effect. In cars, it claims you can run it until the oil turns black because of all the freed up gunk, or 3000 miles. Seafoam seems like one of the few snake oils that people believe in.

But I came here for opinions/stories and thanks for yours! Do you know of anyone hurting an engine with seafoam?

I am usually skeptical on additives but gave Seafoam a try in my ’55 LoBoy I brought back to life. It smoked pretty badly and I figured I had nothing much to lose but the few bucks a bottle costs. I don’t know if it would have cleared up on its own or if the Seafoam did the trick, but I am giving Seafoam the credit.
Something’s you just can’t explain….

“She falls down a well, her eyes go cross. She gets kicked by a mule. They go back. I don't know.”

Good luck,

[Eugene]

I'm on the Sea Foam side. Give it a try. Just follow the directions as to quantities.

http://mgaguru.com/mgtech/engine/ro101.htm
Above article lists a number of possible causes, some may apply.

I turn of the fuel supply at the gas tank at the end of the work day and let the engine run until it dies. This may not be a good procedure if you have frequent stops and starts.

[Scrivet]

............. I'll probably dump a can in the gas tank after that and one or two in the crank case for the winter before I change oil in the spring.

Follow the correct dosage. A couple ounces in the oil is a good thing a couple cans in the oil is not.

I have a spray bottle, probably 3-4 ounces, that makes a fine mist when you pump it. The only thing I don't like about it is the whole top pushes down with your finger so aiming it is a little difficult. Anyway I have Seafoam in it and give a few shots directly into the carb intake. I most recently did this on my nephews 1981 F-350 (gas engine) that doesn't see a lot of use and had developed a high rpm miss. I took off the air cleaner and started it up and sprayed about two ounces of Seafoam with my little bottle directly into the carb intake. I would also run the throttle up some and then spray it again. Seems to have cured the high speed miss.

[danovercash]

4.5 oz. in three qts. Of engine oil max. I use sea foam in the fuel never have in crankcase. One member wasted a Cub engine trying to clean it with kerosene while running.

[Radec Aksarben]

............. I'll probably dump a can in the gas tank after that and one or two in the crank case for the winter before I change oil in the spring.

Follow the correct dosage. A couple ounces in the oil is a good thing a couple cans in the oil is not.

I have a spray bottle, probably 3-4 ounces, that makes a fine mist when you pump it. The only thing I don't like about it is the whole top pushes down with your finger so aiming it is a little difficult. Anyway I have Seafoam in it and give a few shots directly into the carb intake. I most recently did this on my nephews 1981 F-350 (gas engine) that doesn't see a lot of use and had developed a high rpm miss. I took off the air cleaner and started it up and sprayed about two ounces of Seafoam with my little bottle directly into the carb intake. I would also run the throttle up some and then spray it again. Seems to have cured the high speed miss.

Yeah, I way overestimated the amount of oil that goes in the crankcase. The 8 quarts would take 12 oz of seafoam according to the bottle. I haven't put any in the crankcase yet.
I saw those spray bottles and I think that would work well, but I figured I'd try putting it in the gas tank first. I ran it until it reached operating temperature over the weekend and then parked it and shut it down by choking it hoping to get the cylinders a little wetter. I haven't been back to it since.

[Stanton]

Keep us posted as to your progress and results. Wish you the best!

[Rick Spivey]

I suspect your timing may be off, and as much at fault as carbon. However, for carbon buildup, this is my method. I would run the sea foam as suggested in both gas and oil. But for a really bad case, I have also used the "spray it into the carb" method. I run at 1/2 to full throttle, spray until the engine dies down significantly, stop, and let engine catch back up. Do this 5 times, completely killing engine on fifth round. Wait 30 minutes, crank back up. Be ready for a shower of carbon particles throughout this process.

[Radec Aksarben]

I suspect your timing may be off, and as much at fault as carbon. However, for carbon buildup, this is my method. I would run the sea foam as suggested in both gas and oil. But for a really bad case, I have also used the "spray it into the carb" method. I run at 1/2 to full throttle, spray until the engine dies down significantly, stop, and let engine catch back up. Do this 5 times, completely killing engine on fifth round. Wait 30 minutes, crank back up. Be ready for a shower of carbon particles throughout this process.

The spray in method would have been the next thing I tried, but it looks like it won't be necessary! The tractor sat for a week after I "choked" it. I ran it several times this past weekend and it shut right down with the button.
I suppose I will still run seafoam in the oil before the next oil change just to clean out that area too.

[LincTex]

Dump 1-2 tablespoons into each spark plug hole, leave the wires off, and crank it with the starter for 5-10 seconds to get it all over everything. Come back an hour (or a couple days) later, put the plug wires on and fire it up. Hold an umbrella or it'll look like you were in a black rain shower! (or slip a u-pipe over the exhaust)

[Matt Kirsch]

Seafoam can't hurt. I know I've seen it work in three engines now; a Super H, a 240, and a 656. All three were engines that hadn't been run in a while and smoked pretty badly. After adding Seafoam, the engines smoked HEAVY on the next run, but after that ran clean.

I have about six cans of it on hand at any given time, and plan on using it in this '51 Cub I'm working on.

[jsfarmall]

I have never used seafoam in the oil, but I have alot in the gas and I like it. Not to say anything bad, scare anyone, or talk anyone out of it, but I have seen seafoam fry engines. The rest of that story is we did NOT mix according to directions. We mixed it close to 75 percent gas to 25 seafoam in our racing mowers in high school. We had to run factory engines in our HP class and uses seafoam for the extra BOOST and boy did it work!........for a little while lol. BUT anytime i used it according to directions I have had no problems at all. Works great.

[Farmmerjon]

Never used in crankcase before but works great in fuel.