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Driver Side 258 Block Plugs


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Hello all,

While working on the CJ-7 I noticed two plugs on the driver side of the block. Not being able to recall if I had pulled those plugs 20+ years ago when I rebuilt the engine I decided to take a look. From what I found it would appear to be oil gallery access. I was surprised by the amount of rust. At that height it could be the water jacket. 

After I got cleaned out what I could I put some compressed air to it and of course it just vented into the block.

 

My question is oil gallery or coolant jacket and best way to clean it. 

20211202_213059.jpg

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  • Moses Ludel changed the title to Driver Side 258 Block Plugs
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1985CJ7...On the 258/4.2L block, these are coolant plugs.  The plug port further to the right is also low in the block below the expansion plug; this port is for a drain plug.  Though not clear, it looks like you placed a bolt in that drain plug port.  If you remove the bolt, there should be a passageway into the cooling system/cylinder jacket just like the two brass plug ports.  A piece of mechanics wire can probe this and confirm that the passage goes into the cooling jacket.

You can consider whether to install a drain cock in place of the bolt.  The straight threads (rather than NPT threads) at that port accept a drain cock plug.  Light rust at these plug ports is not unusual.  A lot of scale and rust would be a cause for concern.

The camshaft is at the right/passenger side (LHD vehicle) of the block in line with the camshaft, oil pump/distributor drive and lifters.  That would be the oil gallery that feeds the camshaft bearings, lifters, pushrods (valvetrain) and crankshaft journals.  You are on the opposite side, which is the cooling port accesses in the block.  These plugs are at a lower point in the cooling jackets than the expansion plugs to enable more thorough draining and flushing of the block.

Moses

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2 hours ago, Moses Ludel said:

1985CJ7...On the 258/4.2L block, these are coolant plugs.  The plug port further to the right is also low in the block below the expansion plug; this port is for a drain plug.  Though not clear, it looks like you placed a bolt in that drain plug port.  If you remove the bolt, there should be a passageway into the cooling system/cylinder jacket just like the two brass plug ports.  A piece of mechanics wire can probe this and confirm that the passage goes into the cooling jacket.

You can consider whether to install a drain cock in place of the bolt.  The straight threads (rather than NPT threads) at that port accept a drain cock plug.  Light rust at these plug ports is not unusual.  A lot of scale and rust would be a cause for concern.

The camshaft is at the right/passenger side (LHD vehicle) of the block in line with the camshaft, oil pump/distributor drive and lifters.  That would be the oil gallery that feeds the camshaft bearings, lifters, pushrods (valvetrain) and crankshaft journals.  You are on the opposite side, which is the cooling port accesses in the block.  These plugs are at a lower point in the cooling jackets than the expansion plugs to enable more thorough draining and flushing of the block.

Moses

Hi Moses,

Thank you. The two brass plugs are ones I put in yesterday I pulled the steel plugs out and put the brass ones in. The rear plug had some pretty nasty stuff come out. I wanted to know if it was a oil gallery or cooling port because I plan to flush the lower part of the block. 

The substance that cam from the rear hole was rust colored and thick. Didn't smell like oil or coolant.

 

Thank you for your help it is greatly appreciated. 

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1985CJ7...No oil passages at this block section.  Could be "block mud" that came from that hole.  Or I may be misidentifying the threaded hole with the bolt.  It aligns with the two new block plugs but could be a blind hole for a mount used in another AMC or Jeep application of this engine.  There is a reinforced rib section there, which hints that the bolt hole is for a bracket of some kind. 

If you remove that bolt, probe the hole to see if it goes through to the cooling jacket.  If a mounting bolt hole, the probe will bottom.  That may not have been fluid in that threaded hole but rather old, oily debris. 

The factory Mopar parts manual shows the two plugs you replaced.  The drain cock mentioned may just replace one of those NPT plugs as an option...Those two brass fitting ports should be through holes into the cooling jackets.  When you flush the lower block ports, coolant should flow from each of these two ports.

  Let us know...

Moses

 

4.2L Jeep Block.pdf

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48 minutes ago, Moses Ludel said:

1985CJ7...No oil passages at this block section.  Could be "block mud" that came from that hole.  Or I may be misidentifying the threaded hole with the bolt.  It aligns with the two new block plugs but could be a blind hole for a mount used in another AMC or Jeep application of this engine.  There is a reinforced rib section there, which hints that the bolt hole is for a bracket of some kind. 

If you remove that bolt, probe the hole to see if it goes through to the cooling jacket.  If a mounting bolt hole, the probe will bottom.  That may not have been fluid in that threaded hole but rather old, oily debris. 

The factory Mopar parts manual shows the two plugs you replaced.  The drain cock mentioned may just replace one of those NPT plugs as an option...Those two brass fitting ports should be through holes into the cooling jackets.  When you flush the lower block ports, coolant should flow from each of these two ports.

  Let us know...

Moses

 

4.2L Jeep Block.pdf 197.89 kB · 0 downloads

I cleared out the coolant plugs. Filtered some standing antifreeze thru the block and used compressed air from the top passages to push the crud out and there was quite a bit of crud just shy of a cup and a half. Flushed the block until it came out clean and green. I will be putting a coolant filter on the radiator hose like I have on old blue. Planing on a flow kooler pump on there too.

On a related topic I for many years have used only green antifreeze with absolutely NO WATER. My granddad a old farmer tought me that. Since I have not used water in my coolant I have never had to replace a water pump, thermostat, cap or radiator. My grandfather used the logic that without water electrolysis is nearly non existent. 

Unfortunately the last time before now I worked on this jeep was before I put this practice into effect.

I have found also the coolant is good to 20-. I have practiced the is in many engines over the past 17 years with no issues. Not sure if that works with newer engines. 

As far as where I had the bolt I tried wire and finely a punch and lightly taped it. It may have been plugged by a previous owner. 

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1985CJ7...So that was a "blind hole", and the punch bottomed?  As for pure antifreeze, there is a problem.  Pure (not 50/50 premixed) antifreeze cannot dissipate or transfer heat properly without water content.  In extreme cold, pure ethylene glycol antifreeze will actually freeze and crack a block quicker, as the anti-freeze has no ability to yield.

The freezing temperature of pure ethylene glycol antifreeze is around 8.8 degrees F despite a standard hydrometer reading.  Also, because of the expansion rate, the pure antifreeze will make the engine run hotter due to 35% less ability to transfer and dissipate heat.  The boiling point of the typical pure ethylene glycol antifreeze is 387 degrees F.

Prestone all makes all models - Disguised Dexcool? | Page 2 | Bob Is The  Oil Guy

For these reasons, I never run more than a 60% antifreeze/water concentration in an extreme cold weather climate.  (Maximum concentration is 70% antifreeze/30% water, which will drop protection to -84 degrees F.)   60% is good for around -60 to -64 degrees F with a boiling point of approximately 232 degrees F under normal radiator cap pressure.  A 50/50 mix will provide boiling protection to 265 degrees F with a functioning 15 PSI or higher radiator cap.  The higher the concentration of antifreeze, the less boil over protection (lower boiling point).

A 50/50 mix or premix is typically good for -34 degrees F with a cap in good condition.  I always use pure distilled water (non-mineralized) in my mixture to reduce scale and mineral buildup in the engine.  On my Honda motorcycle engine with aluminum head and cylinder, I use non-silicate anti-freeze from Honda.  Silicate, intended to help keep scale from forming, works okay with iron but not so well with aluminum castings.  For the Ram/Cummins diesel and the 4.0L Jeep six, I use Mopar 100,000 mile/5-year antifreeze recommended or an exact equivalent.

As for electrolysis, here's a good rundown on the process and causes:  https://www.northernradiator.com/knowledge/Electrolysis.  One cause of electrolysis is poor engine and chassis grounds that enable 12V-plus current to pulse through the radiator coolant. 

You can actually test for voltage through the coolant with a voltmeter's probes.  Positive probe centered in the neck of the radiator, negative to battery ground if reachable.  A detectable current will show electrolysis caused by metallic buildup in the coolant over time. 

To test current flow through the radiator under electrical loads, this test can be performed while cranking the engine or applying heavy current loads to the electrical system.  If there is higher conductivity, there's electrolysis.  Even in a properly grounded system, there will be a very low voltage reading through the coolant.  The amount of voltage can indicate whether it's time to change the coolant.  Many shops use this test to determine the condition of antifreeze.

Moses

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57 minutes ago, Moses Ludel said:

1985CJ7...So that was a "blind hole", and the punch bottomed?  As for pure antifreeze, there is a problem.  Pure (not 50/50 premixed) antifreeze cannot dissipate or transfer heat properly without water content.  In extreme cold, pure ethylene glycol antifreeze will actually freeze and crack a block quicker, as the anti-freeze has no ability to yield.

The freezing temperature of pure ethylene glycol antifreeze is around 8.8 degrees F despite a standard hydrometer reading.  Also, because of the expansion rate, the pure antifreeze will make the engine run hotter due to 35% less ability to transfer and dissipate heat.  The boiling point of the typical pure ethylene glycol antifreeze is 387 degrees F.

Prestone all makes all models - Disguised Dexcool? | Page 2 | Bob Is The  Oil Guy

For these reasons, I never run more than a 60% antifreeze/water concentration in an extreme cold weather climate.  (Maximum concentration is 70% antifreeze/30% water, which will drop protection to -84 degrees F.)   60% is good for around -60 to -64 degrees F with a boiling point of approximately 232 degrees F under normal radiator cap pressure.  A 50/50 mix will provide boiling protection to 265 degrees F with a functioning 15 PSI or higher radiator cap.  The higher the concentration of antifreeze, the less boil over protection (lower boiling point).

A 50/50 mix or premix is typically good for -34 degrees F with a cap in good condition.  I always use pure distilled water (non-mineralized) in my mixture to reduce scale and mineral buildup in the engine.  On my Honda motorcycle engine with aluminum head and cylinder, I use non-silicate anti-freeze from Honda.  Silicate, intended to help keep scale from forming, works okay with iron but not so well with aluminum castings.  For the Ram/Cummins diesel and the 4.0L Jeep six, I use Mopar 100,000 mile/5-year antifreeze recommended or an exact equivalent.

As for electrolysis, here's a good rundown on the process and causes:  https://www.northernradiator.com/knowledge/Electrolysis.  One cause of electrolysis is poor engine and chassis grounds that enable 12V-plus current to pulse through the radiator coolant. 

You can actually test for voltage through the coolant with a voltmeter's probes.  Positive probe centered in the neck of the radiator, negative to battery ground if reachable.  A detectable current will show electrolysis caused by metallic buildup in the coolant over time. 

To test current flow through the radiator under electrical loads, this test can be performed while cranking the engine or applying heavy current loads to the electrical system.  If there is higher conductivity, there's electrolysis.  Even in a properly grounded system, there will be a very low voltage reading through the coolant.  The amount of voltage can indicate whether it's time to change the coolant.  Many shops use this test to determine the condition of antifreeze.

Moses

Oh I am aware of the Writings to the subject of diluted coolant and I would never doubt those writings. However I have used the method of non diluted coolant for 15 plus years with no cracked blocks, overheating and no noticeable corrosion at all. Something else I failed to mention was how clean and deposit free the water jackets have been on engines I have overhauled.

I know publication and instructions say the opposite but as someone who has used this method it work and well. I only suggest you try it just once. You will not be disappointed.  

I have discussed the method with more mechanics than I can recall and to this day only 3 have tried it will no ill effects. 

For example I have a old car I bought with a bad water pump I used the method with it 14 years ago. I have not even changed the coolant (mostly to see how long the car would hold up). I check the temperature rating every year with no change. The car is now driven by by grand daughter and the last time I looked it has 428,000 miles on it. 

I am not telling this to be a smartass but to possibly help others and share what my grandfather taught me. 

As far as electrolysis is concerned I dont know but I am willing to bet that glyphosate isn't a better conductor of electricity then water. Infact I would think glyphosate mite be a buffer or insulator from the effects of electrolysis and corrosion of dissimilar metals. 

Thank you for your time and consideration. 

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1985CJ7...Like you, I am always willing to learn and try things.  Your experience is valued, and it would be fun to experiment with voltmeter tests on your pure antifreeze cooling systems compared to similar vehicles with mixtures of antifreeze and water...Do keep us posted, I'm very interested in your findings...Thanks, as always, for your contribution to the forums!

Moses

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41 minutes ago, Moses Ludel said:

1985CJ7...Like you, I am always willing to learn and try things.  Your experience is valued, and it would be fun to experiment with voltmeter tests on your pure antifreeze cooling systems compared to similar vehicles with mixtures of antifreeze and water...Do keep us posted, I'm very interested in your findings...Thanks, as always, for your contribution to the forums!

Moses

I am also interested in your findings with the volt meter that will be a interesting experiment. I will be honored to keep you post and appreciate being a part of your fourm. Please also keep us posted with the meter coolant experiment. Looking forward to your findings.

Hope your weekend is a great one.

 

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Have a good weekend, too!  I will update on the voltmeter tests of coolant...Apparently, these tests assign a "normal" voltage, which has become a standard for when to change the antifreeze.  I would imagine that a specific gravity (hydrometer) or protection strip test is still advisable.  I'll look into this further and add details.

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4 hours ago, Moses Ludel said:

Have a good weekend, too!  I will update on the voltmeter tests of coolant...Apparently, these tests assign a "normal" voltage, which has become a standard for when to change the antifreeze.  I would imagine that a specific gravity (hydrometer) or protection strip test is still advisable.  I'll look into this further and add details.

Thank You Moses 

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  • 1 year later...
On 12/3/2021 at 3:00 PM, 1985CJ7 said:

Hi Moses,

Thank you. The two brass plugs are ones I put in yesterday I pulled the steel plugs out and put the brass ones in. The rear plug had some pretty nasty stuff come out. I wanted to know if it was a oil gallery or cooling port because I plan to flush the lower part of the block. 

The substance that cam from the rear hole was rust colored and thick. Didn't smell like oil or coolant.

 

Thank you for your help it is greatly appreciated. 

1985CJ7, where did you buy the two brass plugs to use in place of the steel engine block coolant drain plugs?   

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Hi, Cj7RestoClassic...Brass pipe plugs like you see in 1985CJ7's photo are available through automotive machine shops and their suppliers.  They are not common "Lowe's" or "Home Depot" plumbing plugs, as you have likely discovered.  Internal hex inserts are common in brass, as shown here at Amazon.com.  With proper sealant, these would work if you want to use brass:

https://www.amazon.com/s?k=engine+npt+plugs+brass&crid=U1TUY6MIE72U&sprefix=engine+npt+plugs+brass%2Caps%2C169&ref=nb_sb_noss

Here is a link to the Dorman 090-019 steel plug with a 5/16" square insert size.  It was used by Chrysler from '84-'86 as well as Ford and GM on engine castings (head or block).  AMC may have used this as well...The plug is NPT 3/8" size: 

https://www.dormanproducts.com/p-26544-090-019.aspx 

Dorman follows the OEM use of steel.  Looks like a zinc coating...At the link I provided above, you will find a long list of vehicles/engines that use this plug.  If your size is 3/8" NPT, this would work.  

Moses 

 

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