i have a 1978 dodge d100 pickup with a /6 i rebuilt 2 years ago. the engine overheated and blew out my radiator. i had it rebuilt, put in a new water pump, thermostat and head gasket (this time a metal one). i have checked for leaks, plugged up hoses, made sure the water pump works, etc, but still the engine runs at 230-245 degrees. im now adjusting the timing and have been running it at 9-11 degrees. anyone have any suggestions on what is wrong or any advice on what to do next?

Check the heater box to make sure it's not plugged up (you can back flush it with a garden hose), what temp thermostat are you running(195), what kind of fan are you running (stock 4 blade)?

Have you checked for any exhaust leaks? these can heat up your engine bay in a hurry....


-D.Idiot

Also remove the plug on the side of the block (near the oil pressure sending unit, a few inches away from it, 4 sided if I recall....) and see if there is any debris jammed up in there. That is a common place for clogs to appear from antifreeze or additives over the years. If it is clogged then you have to scrape away at it with a screwdriver or similar impliment to clear it up. If you remove the plug and no coolant or very little comes out... thats most likely your issue.

thanks for the suggestions, i have flushed it with a hose to no avail. i have a 185 thermostat on it with a 6 blade fan off a v-8 engine. im trying to adjust the timing some more right now, but the engine temp is the same, all im getting is some power loss. ill try that plug next and update this. any more suggestions are welcome.

just went out to find the plug, the only one i found was back from the oil pressure sender about 3-4 inches and was a 9/16 hex head. tried to pull it out and broke it-yeah im real happy. anyways, i have a dodge book from 1978 that tells me all about the truck and engine and i cant find that plug-whats it for? i havent tried flushing the heater core yet, but i have good heat when the engine heats up-do i still need to flush it? thanks for all your help.

Pierre, have YOU ever removed this particular plug? Did coolant (or anything) come out? Just curious.

"DW"

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If it ain't broke, fix it!

This is a large plug, used a pipe wrench to remove mine, thinking about replacing it with a drain cock for future service ability. Was able to do a through flush with this removed...Dave

OK, I'm gonna have to plead "ignorance" on this one... On all the /6 blocks which I've ever removed this plug (which admittedly is a VERY small subset of the overall population of /6 blocks produced), it was an unmachined hole to nowhere. In silence, I wondered the purpose of such a plug. So am I to understand that it is machined all the way through the lifter galley to the water jacket on some blocks? Calling all block experts!... What do you know about this, Doc?

"DW"

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If it ain't broke, fix it!

so far out of the 5-6 of these that I've stripped out for parts and had to drain, all spewed either coolant or the brown baby crap sludge (some people just don't change their coolant often enough...)

This 9/16" plug is for the coolant jacket around the cylinder bank....




If you take a look it goes right though the lifter bank where the reinforcement web is and looks to be just above the oil passage and misses the lifter bores....




If you got one that's unmachined I'd be curious to see some pics of that....

-D.Idiot

Mine has a heater hose running to it...that is where I installed my electric circulating heater. Needless to say, antifreeze spews from this hole on my block.

Have you checked the coolant temp with a thermometer to verify the temp gauge is working (reading) correctly?

-S/6

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The "Silver Bullet"
87 Ram D150

This plug is the drain for the water jacket, it is placed so most all the coolent can be drained from the block.
Use this plug to drain the block before you pull-off the cylinder head. (engine in the car) Doing this keeps a bunch of coolent from going into the cylinders.

This water jacket hole is also handy for other things like engine flushing and heater / curculator access.

Seeing this plug / hole is at one of the lowest points, it is common to find a bunch of sludge covering it.
What DW thinks is a unmachined hole is really a passageway completely packed and clogged with crud. (Why would the factory drill, tap and install a plug into a blind hole??)

Unscrew the plug and start digging, sometimes the crud is so "baked-in" that I have to use a drill bit to get through, you will hit water with some work.
DD

Dennis,
Yep I have removed it when my engine was overheating for no apparent reason, and no nothing came out untill I kept digging around it. Put it back in with some antiseize if you can get it out so it will be easier to remove next time.

I guess anything's possible... Sure looks like solid metal to me. But I agree this is rather nonsensical. The plug in my Duster is one of the "solid" ones I've run across... I'm going to pull it and conduct further study. Will report findings.

"DW"

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If it ain't broke, fix it!

Report Findings:

Well, a double dumbass on me. I had to know, so I jacked up the car and removed the plug. Sure enough, the grey-est most smoothly metallic looking blind hole. So I prodded. And poked. And eventually I chipped a few hard crumbs out of it. Sure enough, some of the hardest most baked in black iron oxide ever. Would have to be drilled out, as Doc pointed out. Turns out it made a nice smooth impression of the back of the plug. The block's been hot-tanked and all the usual prep. I'm not the least bit worried about it, I have no cooling problems or loose gunk in the system, but the mystery's been solved, for me at least.

"DW"

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If it ain't broke, fix it!

thanks for all the advice-the pictures were most helpful. in response, i did check the water temp and my guage and sender are correct. only problem is i cant get go the freeze plugs due to the manifolds, have to do it later and the bolt in the drain next to the oil filter-how long is that bolt? i think i may have broken it off or it may be like what was said that junk is in the hole stopping it up and i wanted to know how long the bolt was before i drill anything.