"Hot soaking" for improved mileage.
 

I did a search on this, and apparently no one on the board has mentioned one of my favorite tricks for cleaning a motor and getting optimum performance.

It's the hot soak. A variant of it has been around since the 1960s, when a mechanic demonstrated it at the North American International Auto Show as a way of cleaning lead-fouled combustion chambers. I've done it on my car every 3000 miles since I bought it at 136,000, and it's running strong at 193,000.

The procedure is very simple indeed. First, locate your fuel pressure regulator. It's a small vacuum line running from the front of the intake manifold, in most cases. The major repair manuals (Chilton, Haynes, Bentley) all show it clearly.

You'll need a can of Seafoam fuel treatment for the soak. Other treatments work, but none so well as Seafoam in both my experience, and the experience of the BMW mavens on Unofficial BMW. I have used Lucas treatment in a pinch. Seafoam's worth the 10 bucks.

Start your motor, and disconnect the end of the hose from the fuel pressure regulator that has a vacuum. Touch the end to be sure there is a vacuum present, and put that end into your can of Seafoam so it's just drawing off a mix of liquid and air. The motor will struggle a bit, and if it does, let it draw air for a second. It still shouldn't take more than a minute or so to get the motor to ingest the entire can.

One of two things are going to happen when the can is nearly empty. One, the car may stall. If you're down to only a couple ounces left, reconnect your line and leave it be. If it's taken the whole can and hasn't stalled out, shut off the motor manually.

Now for the hard part. Walk away for 8-12 hours. Yes, walk away. Close the hood, lock the doors, walk away.

After letting it sit, go for a drive. It will smoke worse than you have ever seen, guaranteed. Vary your speed for a while, and eventually the smoke will clear. The motor is now clean.

Go get your oil changed, as the soak frees any deposits in the combustion chamber and dumps them into your oil sump. Now your motor is clean, you have fresh oil, and will probably see a performance gain- mine always does! :D

I'm tempted to say that the hot soak was key to the mileage gain I have seen. When I bought the car, it had been largely neglected for a year- low octane gas, no oil change for 13,000 miles, and so on. I got 14mpg out of the first tank of gas. After a hot soak and an oil change, I got 19 out of the next tank with the same driving habits.

Thanks for the info Casey!

There is something similar that some people use, but we call it Seafoaming the engine.

Just a clarification for Honda owners; don't disconnect the vacuum line running to your fuel pressure regulator, doing so will bring up fuel pressure to that of WOT (Wide Open Throttle) and dump too much gasoline into your motor along with the seafoam.

The recommended way to do it (if you don't have a spray bottle to use to spray the seafoam into the Throttle body) is to use the large vacuum line running to the brake booster.


The way that I do it for my VX:
1) Remove the rubber arm from the airbox to the throttle body

2) Put seafoam (or GM Top Engine cleaner, from the dealership) into a spray bottle

3) runn motor up to operating temp and spray the cleaner into the throttle body/intake area until the full can is gone (pushing on the throttle as needed to keep the motor running during the process)

4) shut off motor and let sit for at least 15 minutes or more like 30-60 minutes

5) start up motor and fog for mosquitos for the next 5-10 minutes ;)

6) change oil and enjoy the smoother running engine.

:confused:

that would be a sign of needing rings or valve seals.
seafoam is a targetted product that has had many many alternatives over the years...in fact my local parts store, nor any that I have found even carries it. The internet told me about it.
personally, carb cleaner for top end and engine base cleaner for bottom end (many brands). The chamber is not the base pans world. why connect them , even with a chemical that leaves?
and the most imporant clean of all is a very very high powered high pressure burning hot steam clean with a powerful cleaner added...on the OUTSIDE of the engine.

And to think i used to use just plain old $0.99 ATF to clean the gunk out of engines ..........

Disconnecting the exhaust before the cat is a good idea as well, if its got a joint.

Always figured it was wrong as I never saw excess crap in the oil, but didn't know if that were universal.

The soak works for me. That much I know and have the stats to prove.

You could always follow the directions on the seafoam can, as well. Something tells me that those directions are there for a reason.

Not bashing you, but using the whole can doesn't get you any better result than doing what they tell you on the can, unless you have a seriously messed up engine, in which case you should be repairing whatever caused the problem, not putting a band-aid over it.

There has also been discussion here before about the idea that seafoam has never really been empirically proven to work, since noone has ever taken before/after pictures of the piston tops and combustion chambers. The smoke could merely be a by-product of the chemical in the can. Pour ATF down your carb throat, you get smoke. Same principle.

Lastly, solidified carbon is resistant to chemical solvents. It's like plastic, basically. It can be removed with abrasive cleansers, and with heat/cooling cycles, or with peening techniques, such as water spray into the intake. SeaFoam will not remove solidified carbon deposits, unless they're already loose.

I've done this a couple times and it works well. Ive heard that BG 44k is better though. Im going to try that next time (it is also much more expensive at 25 bucks a pop).

I do it similar to this with a few differences
OUr mercedes and my el camino have upwards facing air intakes Fuel injected and carbed

1. I take off the air cleaner and slowly pour it straight down the intake manifold using a little throttle to keep it running till i've put half the can in the intake. Turn the car off put the other half in the cranckcase.

2. leave it to sit for 15 minutes.

3. Start it up let it run for about 5 minutes. Rev it a bit to make sure the car stops smoking AS much

4. Take it on a briisk drive to get ALL the gunk out of the system

5.Then Do the oil change

Works pretty well for me with all the cars i've done it on Well worth the price:D

Just wondering Have you ever used seafoam?

If so what were your results

Polyether amine is your friend. Chevron Techron Concentrate, Gumout Regane, Amsoil PI all have lots of PEA. It's supposed to work quite nicely on carbon.

Water injection works well, too. As long as it's not much water, and is introduced where it can get to all the cylinders.

Pictures I don't have, simply results and my own experience opening up the engine.

As for the results, when I first bought the Red Storm in '04, it was getting a very precise 14mpg city. Changing up to 93 octane brought it to 17mpg. The first hot soak brought it to 20mpg, with no changes in driving habit. I'd say 3mpg is worth having.

When opening the engine, I have stripped it down to replace the timing chain and tensioners. The inside of that engine is cleaner than my old Taurus was, even though the maintenance program was the same and the Taurus was 50,000 miles newer. :)

We used to use a Binks #7 commercial spray gun (for painting cars) and water to remove the carbon in Nissan Z car engines. The 81-83 models had a combustion chamber design that had about 33% of the piston top (flat top piston) within 1 MM of the cylinder head. When enough carbon accumulated there it would sound like the engine was coming apart.

Used vice grips to set the throttle at 2k RPM and sprayed the atomized water into the intake. I know it worked and many of my customers did not have to get it done again for years.

No need to change the oil, although we usually did it after we had confirmed the carbon knock was gone. We could look through the spark plug holes to see the piston tops, but the carbon knock was the reason we did the procedure.

I once towed a car 180 miles with the customers approval to replace the engine, and fixed it with this process in less than an hour, without disassembling any part of the engine other than the air cleaner assembly.

I do use BG 44K, but only about once a year. Newer design fuel injectors seem to have minimized the old spray pattern issues with the early pintle type injectors. Ethanol probably helps some also.

regards
Mech