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JSoko August 2nd, 2012 07:45 AM

How to Seafoam your engine the RIGHT way:
How to Seafoam your engine the RIGHT way:

There’s a lot of misconception out there about products like Seafoam, so let’s start with clarifying the purpose for the product, why you’ll want to use it, and how it’s used.

One of the by-products of combustion is carbon, the black soot that can gradually collect and harden on the cylinder head, cylinder wall, piston and valves. Carbon deposits accumulate in the combustion chamber and on the valves and pistons. These deposits have a measurable effect on engine performance, resulting in higher oil consumption, reduced fuel economy, engine knocking (pre-ignition or detonation), hard starting, higher emissions and even overheating.

Engines that make a lot of short trips at low RPM’s are more susceptible to engine deposits, but the truth is, all engines will develop carbon buildup over time. Regular application of a decarbonising agent such as Seafoam is the only sure way to prevent carbon deposits from hampering engine performance. If you have a higher-mileage car, it’s a safe bet that there’s some significant carbon buildup.

This is a fun little maintenance project. Get two cans of original Seafoam. For those of you who will be doing this procedure on a higher-mileage car, I recommend being prepared to do an oil change AND change your spark plugs soon afterwards – they’re probably due anyway, right? Make sure your fuel tank is at least half-full (actually, half-full is ideal).

Other than that, you’ll need a length of smaller-diameter rubber hose (I use vacuum line hose), a funnel, a helper, and an open area with good ventilation. NOTE: You’re going to make a TON of smoke, so make sure you’re not next to a funeral home, a police station, an EPA office, or your Homeowner’s Association President’s house. In fact, for reasons I’ll get into later, I prefer to do my Seafoam application late, late at night.

I’ve used Seafoam products for 25 years with great results, so let’s get you started.

Get the engine warmed up to operating temperature. While the engine is running, disconnect any main manifold vacuum line that feeds ALL the cylinders. For most cars, the brake booster hose works great. If you DON’T know which hose to use, post up on the forums to get an answer. Make sure you don’t pass Seafoam through the check valve – You’ll want to bypass the check valve, which, on many Nissans is located in the middle of the brake booster hose, up against the firewall. Disconnect the hose so that the check valve remains on the hose that goes TO the brake booster – Using the brake booster hose that goes towards the manifold, and insert a length of smaller hose into it, so that you get a tight seal. Now, some will say to pour the Seafoam into the hose. I don’t like this method, because you can spill it, you can dump in too much at once, or you can lose track of how much has gone in.

I prefer to dip the end of the hose into the can like a straw – Pretend you’re “sipping” the Seafoam out of the can. You’ll know you’re doing it right if the engine stumbles a little on each sip. Tell your assistant to keep the engine running, but not to give it TOO much throttle. Stay at or under 2,000 rpm’s. Don’t let it “chug” the Seafoam – Remember, small sips. You should be 1/3 to 1/2 of the way through the can in the first minute or so. You’ll see small amounts of white smoke from the tailpipe – Don’t be tempted to rev it hard – We’ll get to the REAL smoke show in a minute!

When you get almost halfway through the can, dunk the hose into the can, give it a good “chug” and let it stall the engine (or have your assistant shut off the engine immediately). I like to give the “3…2…1…” countdown to time it *just* right. This will leave a good, wet dose of Seafoam on the cylinder tops and valves, where it can soak into and dissolve the varnish deposits that hold the carbon together. Let the engine sit for 30 minutes. While it’s sitting, dump the rest of the can into the fuel tank (use a funnel).

Now, restart the engine and go for a drive, someplace where you can drive the car hard. Make sure your windows are rolled up, you don’t want to stink up your interior. You don’t need to go far, and there’s no need to go getting a ticket, but I like to find a road where you can do a couple good 0 – to – 60 pulls at wide-open throttle without getting into a lot of traffic. You’re going to dump a TON of smoke, so there’s another reason I like to do my Seafoam treatment at night. Drive 5-10 miles and park the car. Let it cool down. The next time you drive, you’ll notice some residual smoking, and it’s gonna stink – don’t panic, you’ve got a lot of crap burning off. It’ll go away.

OK, you’ve got another can of Seafoam, right? Good. This can is going to be used to clean oil rings and lifters, clean built-up oil residues and contamination from the crank case, and clean the PCV system. You’re going to use 1.5 oz per quart of oil. Check your owners manual (or, again, ask on the forum). If you have a 5-qt oil capacity, you’ll be using 7.5 oz of Seafoam (roughly half a can). While the company claims you can leave the Seafoam treatment in your crankcase until your next oil change, I’ve found that most engines with higher miles have a LOT of nasty buildup, which can really take a toll on your oil filter. Therefore, I like to do an oil change roughly 50 – 100 miles after adding Seafoam.

The other half of the can? Add it to the crankcase after you change the oil if you had a lot of sludgy buildup, OR dump it in your fuel tank at your next fill-up. Seafoam is safe to leave in the crankcase with clean oil until your next oil change, and it’s also a great product to clean your injectors and fuel system. In fact, it’s even credited with helping remove some of the deposits that cause a faulty fuel gauge reading in some cars!

Have fun, be safe, and enjoy your clean engine!


The Frankster August 4th, 2012 08:48 AM

Just bought a can yesterday, great info J. I'll go back and buy another today. Sounds like what my Uncle use to do except he would pour tranny fluid down the carb. Smoked up half the neihbor hood (LOL).

JSoko August 4th, 2012 09:11 AM

in the 60's & 70's transmission fluid was the thing

skatebowd August 4th, 2012 10:44 AM


Originally Posted by JSoko (Post 64980)
How to Seafoam your engine the RIGHT way:


Adrien December 9th, 2018 06:01 PM

Is it safe to assume that if your truck did not dump a ton of smoke, it is pretty clean?

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