Press "Enter" to skip to content

S401 Upper Engine Cleaning

Now here is a job that everyone loves to do. Upper Engine Cleaning, AKA, the Smoke Screen.
To add to my “worked on my car every day after work this week” target, I decided to give some Subaru Upper Engine Cleaner a shot and see if it changed anything with how the car is running.

Subaru must think its a fairly important thing to do, as they recommend using it every 12,500km or so. Its designed to remove carbon deposits, varnish, etc etc, all the stuff you don’t want in your intake or combustion chamber.

It comes in a little spray can, with a hose to direct the spray. Nothing too fancy, and likely made by someone else (Bar’s, apparently).

The basic idea is that on a stopped, warm engine, you pull off a convenient vacuum line from the intake manifold, stick the hose in it and pull the trigger on the can. Empty half the can into the intake, and let it sit for 5 minutes. Start the car, and empty the rest of the can into the intake with the car running.

I found it easy to pull off one of the hoses at the front of the manifold, staring right at you. Didnt have to remove any covers or anything.

Stick the hose in, and spray spray spray. Working out how full the can is, is a real prick though.

The first startup with this stuff in the engine is hard, it’ll crank and crank but eventually it’ll catch and lumpily start to run. Some cars have plumes of smoke, but in my car I had only a couple of small puffs. Same deal with spraying when running, i got barely anything from the Subaru cleaner.

Needless to say, I was a bit disappointed by the lack of awesome smoke clouds…. so I decided to give the can of Mitsubishi Shumma that I had in the garage a shot. Shumma is hard-core, it’s used to clean solid carbon out of the diesel engines used in Mitsubishi Tritons and Pajeros.

Same deal, it’s a can with a hose.

This time was different. The first startup a got a couple of small puffs, but when spraying it into a running engine I got some nice solid clouds coming out of the exhaust.

Once I was done spraying into the running engine, I left a little in the can and sprayed it into the intake again with the engine off. I left it for 10 minutes, and then took it for a decent spin. Plume of smoke on startup, but otherwise seemed fairly clear on the drive.

The verdict? Shumma is better than the Subaru stuff. I swear Subaru changed the formula a few years ago and made it less potent. Shame. Oh, and the car seems to be a bit smoother, the engine is more responsive, but it still hasn’t cured the low down bogging or idle lumpiness.

I have a set of good, used coils on the way, and a new McIntosh speaker to replace my blown one. I also have a cabin filter, and some steering rack bushes that need to go in at some point.

Im slowly but surely chipping away at it.

0 0 votes
Article Rating

Discover more from Tastes Like Petrol

Subscribe to get the latest posts to your email.

Notify of

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Inline Feedbacks
View all comments