That's talking about the pipe plugs, not the freeze plugs.Here's the excerpt from page 43 of the 1974 Plymouth Duster Owner's Manual. Perhaps I've misunderstood it. It says to "remove the drain plugs in the sides of the cylinder block". I took this to mean the freeze plugs because I can't find any "drain plugs" in the side of the block. So now I'm assuming that they are referring to the single plug that I posted a photo of. I guess what I'm wondering is if you do a better flushing job by using the backflushing tee instead of draining the block like the owner's manual says. To me, it seems like using pressurized water to blow everything out of the cooling jacket is better than simply using gravity to drain coolant out of a hole. Your thoughts?
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My rad is filled to the propper level, no fluid comes out. If you over fill it then yep
I first found the correct part number in my 1974 parts catalog (see photos), then bought a NOS one on e-Bay about a year and a half ago. I don't remember the name of the vendor. As an aside, I visited my favorite junkyard in western MN to find a spare radiator for my Duster at that same time. The slant six radiators are getting really hard to find, but I found one still with its factory original cap. The cap looked pretty worn, but I popped it on my Duster and it worked perfectly! Sorry, too much information - I know.cruiser? Where did you find that nos radiator cap?
So will the iron out I suggested.it was originally marketed for cleaning the same type of deposits out of boiler radiators, and I have some old Prestone flush cans that are exactly the same thing (sp?) Oxalic acid. Flush with water til as clean as it can be, add a cup of iron out, finish the fill with water, drive a bit to circulate it, if real bad let sit with this in it over nite, pull block drain and radiator drain and flush with water again til clean, fill er up and let er rip
1971 slant 6 cylinders block drain instructions :
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(picture from Home - Mopar DiY)
François
You said drain ****....
Drain **** is what happens when a man pees....
I’ve been turning cars upside down to drain coolant since my father taught me years ago.
Yeah, the cornfusion came from the generic service text, using the identical service text as the V-8's w/o distinguishing the Slanty. Plural plugs had You eyeing the core hole plugs, & as above, fooling with more than needed can cause other problems to pop up. Happy cooling!Thanks, everyone for the great suggestions. After reading through the replies, I think I may end up taking TF360's advice, to just leave the side drain plug in place and keep backflushing it as I have in the past. I have a bad feeling about trying to get that plug out after it has been in there for the past 34 years. Usually, I just foul it up somehow and end up opening that can of worms that he mentions. Toolmanmike asked why I feel the need to remove every drop of dirty coolant from the system, which is a good question. There's no logical reason, other than I'm a bit obsessive about purging old coolant. Since 2019, I've replaced the incorrect radiator that the car came with and installed a correct part number recored and rebuilt radiator. I've also replaced the water pump, thermostat and housing, heater core, all heater and radiator hoses, and installed a NOS correct part number (one year only for 1974) radiator cap. There's nothing left to replace in the system, and it cools beautifully. Thanks again to all who took the time to weigh in with their opinions. You guys have been extraordinarily helpful in keeping my 49 year old car running like a brand new Plymouth. Muchos gracias!
I would not knock out the plugs unless they are rotted or leaking there should be a drain plug on the right side if the blockHi Mopar guys and gals: Cruiser here with a cooling system question. I'm pretty particular about keeping up the cooling system in my bone stock 1974 slant six Duster. The owners manual says the proper way to change the coolant is to knock out the freeze plugs in the side of the motor to drain all the dirty coolant out. I've never done this in any slant six car that I've ever owned. First of all, I wouldn't know how to get them out or back in. And second, they're nearly impossible to access as they're under the exhaust manifold. Looks like there are four of them back there. In any case, I've been backflushing my cooling system with a backflushing tee in the 1/2" heater inlet hose for a number of years. Seems to do the job very well. But now I'm thinking that I might be trapping some dirty coolant in my engine because (I'm assuming) the thermostat is closed during the backflushing process, and I haven't knocked out the freeze plugs. There's also another plug in the right side of the block under the #5 spark plug (see photo). What does this do? Does it drain the block? So the question is: How thorough of a job does backflushing my cooling system do? Thanks.
Only in the top of the rad tank for expansion. It does not travel through the system, as the inlet to the pump is from the bottom of the rad, no air down there.I agree thats true but your still allowing air to be in the system
Only in the top of the rad tank for expansion. It does not travel through the system, as the inlet to the pump is from the bottom of the rad, no air down there.
Yes I did. It's entitled "1974 Plymouth Gold Duster Restoration and Walkaround".Cruiser, did you do a video on your car? brown Gold Duster/snake skin top and fold down rear seat? very nice car indeed!
Bill, I'm not sure that the drain plug is 3/8". I just put a tape measure on it and it looks like 5/8".The slant has a single drain plug, 3/8" NPT on R side. I put knock sensor from a Chevy 1985-95 V-8 there (w/ 1/4" NPT bushing) for later use w/ an engine controller. No fan of the old Prestone flush kits which install a tee in a heater hose. I flush a few times w/ tap water, then add 1 lb citric acid and drive for a few days, drain flush fully, rid all water (w/ heater core change), and use Evans Waterless coolant for no future corrosion worries. I change all 5/8" hoses to silicone. Did this in all my vehicles, even 2002 Chrysler T&C w/ rear heat. No more coolant issues or worries.