Steam can be your friend

Another use for vacuum ports.

This tip came to me via ASE Master Tech Chris Spencer; it is used where high mileage engines are failing the Nox aspect of tailpipe emissions despite working EGR subsystems.

I tried it yesterday and it works.

I have had a problem with detonation which has not been solved by cooler plugs, timing adjustment, or higher octane gas or additives.

Detonation is a really bad thing. It is also called "death-rattle."

The engine is designed for 87 octane, unleaded.

I did a compression test which showed (with two gauges to verify findings):

#1 = 165
#2 = 150
#3 = 150
#4 = 170

so #1 and 4 appear high

14.7 X 9.5 should be 139.65.

The engine has 48,000 miles on it, with the original valve stem seals and rings, so compression has probably crept up because of carbon buildup due to oil use.

This repair saves removing the head to scrape carbon off the piston dome. If you are going to be removing the head anyway, this is still a good way to clean the piston domes of the carbon build up before cylinder head removal.

I got the engine good and hot, running it at about 4k rpm, while doing this work.

First, I pulled a plug 4 and measured compression. I didn't do this proceedure on cylinders 2-3, and they were at my final value on cylinder 4, the one that started out at 170 psi.

I reinstalled the sparkplug, and removed the #4 vacuum port plug on the manifold, attaching a 3 foot section of 1/8" or so vacuum hose. I then started the engine, ran it up and locked the rpm with the throttle lock. You could probably do the same thing with a pair of Vise-grips clamping the throttle, braced against the brake lever. Or a pair of channel locks, with a rubber band or two around the handles to provide the clamping. Or maybe get someone to help you with this mad science.

With the engine running at 4k, I then stuck the other end of the hose into a measured container of water. I allowed the engine to draw in about 2oz of water, which immediatly turns to steam inside the hot cylinder. The thermal shock breaks the carbon off, where it gets blown out the exhaust. The cylinder being treated will cut out some, but the other cylinders will keep the engine running.

Between water applications, I let the cylinder I was working on get hot again, by spacing out the water doses. I ran 16 2oz increments through cylinder 4, then checked compression again. It had dropped to 150 psi.

I repeated the proceedure on cylinder #1, and also saw a post-proceedure pressure drop.

The little bit of riding I have done indicates that the pinging has abated substantially.

:woohoo:

So this is an option that doesn't require a major time investment or a lot of tools to see results.

And gain some piece of mind.

KaZooCruiser wrote:

I did a compression test which showed (with two gauges to verify findings):

#1 = 165
#2 = 150
#3 = 150
#4 = 170

so #1 and 4 appear high

14.7 X 9.5 should be 139.65.

Is this equation atmospheric pressure x compression ratio ?

That's what it looks like to me..

water injection has been used since a motor was first built, it does clean the carbon off the pistons, but that has always made me wonder what was causing the excessive carbon build up in the first place

I was told that a thin layer of carbon is good,like
wrapping your exhaust it passes more heat out the exhaust.

Yep it works good. When a head gasket blows and coolant goes in the egine it will make those pistons look new with zero miles. Been doing this for years.

If you get more water in than can be vaporized you could hydralic lock a piston and break a rod.Water
injection needs to be regulated properly.

Pls. be careful in using this technique,too much water in there is an engine death sentence.

Agreed, and there are some "bigger, better" things to shove in there anyway. Suck up a can of sea foam through the vacuum lines, for example (instructions are on the back of the can).......or GM Top Engine Cleaner if you have a GM dealer around.

...and be ready for the big cloud of white smoke!