Water bypass delete

One modification I like to make to Mitsubishi 4g3x engines is to delete the water bypass line behind the water pump.

The car has this originally for use in cold weather countries where the car would be equipped with a heater. The bypass line takes hot water from the engine and runs it through the cars heater then back into the engine. For our cars not equipped with heaters, this is then just an additional liability being made of several rubber joints and hoses that will eventually leak. The copper pipes used for the bypass are also prone to cracking and corrosion over time.

I had to make some preparations today to do this modification for a clients engine so I figured it would be a good opportunity to document how exactly it's done.

Here's what the original water bypass line looks like. A copper pipe running along the exhaust side of the engine block with some rubber joints and a hose or rubber plug at the other end behind the intake manifold.

 The copper pipe and the rubber hose connecting it can easily be removed by undoing some bolts that hold it to the block and the clamps on the hose. You'll be left with a little copper pipe stub at the engine block behind the water pipe.

 This is force fitted to the block and can be removed by simply using a vice grip. Some gentle persuasion using a hammer may be necessary in some cases.

 With the copper pipe removed from the block, you'll be left with a hole.

This hole is then cleaned out and tapped so it will have thread so we can close it up with a plug. I used a 16mm diameter hand tap.

A bolt matching the thread of the hand tap needs to be purchased. I used a T304 stainless steel bolt in my original engine build, but lately this specific size has been hard to find in stainless steel, so for this build I had to use a high carbon steel bolt. Either will do, just don't use cheap ordinary bolts.

Trim the bolt to the right length so it won't protrude into the water pump.

And that's it! Be sure to use a good amount of high temperature silicone during the final assembly to really get the plug fixed in place and prevent any leaks.

This is how it looks like in the final installation on my 4G33.