Help with what water ports are used for

[Harrinad]

Hey, I am working on a 1980 Jeep J10 with the 258. There are two ports on the drivers side of the block that had vacuum lines on them but they seem to go into the water jacket. What are these used for and can I just plug them?

[Tripwire]

HI I

[Harrinad]

Sorry, I

[Harrinad]

I don

[MysticRob]

It's a bug, has to do with apostrophes (obviously). Go back in one of your original posts and edit what you wanted to say. Then hit submit.

[Ristow]

Hi don. Me Ristow.


You cannot use apostrophes it posting from a phone or similar.

[Harrinad]

Thanks, Rob.

[jpcoutts]

In response to your original question I think you are referring to temperature controlled switches that were part of the emissions control system. Most I have seen were simply no longer in use or had the ports blocked. There are plenty of sources for the original diagrams if you want or need to get them back to original but if you don't need that just make sure your vac controlled systems like dizzy advance and the like are getting vac from an appropriate source, manifold vac or carb vac. The folks here can be of great help with specific questions if you post them.

[Harrinad]

How do the temp controlled switches work? Do they only supply vacuum when warm or what? There is no water transfer into those lines, right?

[Cliff]

Correct - just vacuum.

[tgreese]

Do you have the TSM? It will tell you about stuff like this. https://www.rockauto.com/en/moreinfo...183272&jsn=379

There is a '79 and '81 TSM at the Tom Collins site free to read and download. The '80 258 engine is more a '79, and the rest of the truck is more like an '81. https://oljeep.com/edge_parts_man.html

Best to get the exact book for your year. Not expensive.

[FSJunkie]

They were just wax pellet switches. They work the same way your thermostat works. They reach a certain temperature then open or close vacuum ports to control various engine functions.

Typically:

The front switch had two ports and opened at 115 degrees. It prevented EGR from occurring when the engine was cold. Cold engines can't handle EGR.

The rear switch had three ports and switched at 160 degrees. It sent manifold vacuum to the distributor advance below 160 degrees and switched to sending ported vacuum to the distributor above 160 degrees. This advanced the ignition timing while the engine was cold to help improve cold weather performance.

Basically the front switch is only needed if you have EGR and the rear switch just helps the engine while it's cold.

[MysticRob]

They were just wax pellet switches. They work the same way your thermostat works. They reach a certain temperature then open or close vacuum ports to control various engine functions.

Typically:

The front switch had two ports and opened at 115 degrees. It prevented EGR from occurring when the engine was cold. Cold engines can't handle EGR.

The rear switch had three ports and switched at 160 degrees. It sent manifold vacuum to the distributor advance below 160 degrees and switched to sending ported vacuum to the distributor above 160 degrees. This advanced the ignition timing while the engine was cold to help improve cold weather performance.

Basically the front switch is only needed if you have EGR and the rear switch just helps the engine while it's cold.

Too bad this version of vBulletin doesn't allow upvoting or appreciating posts, cuz this is a great one. Thanks, FSJunkie!