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The Cooling Jacket Drain Plug (what size drive?)

Rick Anderson

NAXJA Forum User
Location
Lusby, MD
Sorry guys I searched, seen some reference to it, but no solution or specific size.

Whats size Square Drive is needed to remove the Water Jacket Drain Plug? Its somewhere between a 3/8" and 1/4", ones too big and the other too small, I need one that is JUST RIGHT.

This is a '95 2.5L L4, but I'm sure they're the same size as the 4.0L.

I'm flushing out the cooling system, since the radiator was leaking and the prevous owner had added several different kinds of "STOP LEAK" additives in a vain attempt at stopping the leak. Now the entire cooling system is coated with gunk and shiny copper colored particles.
 
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5/16" or 8m/m - either should work. Make one from a cheap 8m/m hex key by grinding down two opposing corners until it just fits.

If you're going to take that plug out, would you please try to measure the threads on it? I haven't had any of mine out yet, and I've been kicking around the idea of doing away with that plug and putting a brass valve in...

5-90
 
Thanks,
I figured I was going to have to grind down something to fit it, thanks for the idea, a hey key is cheaper than a 3/8 extension that I was originally considering.

I'll let you know on thread size, BUT, I'll use a steel plug. I've noticed the brass fittings I've used (usually "T"'s out of plumbing fittings, for mounting aftermarket Oil Pressure Guage while keeping the original Idiot light) usually start to leak eventually. I've also noticed that every plug/fitting I've seen OEM in engine is steel/iron and not brass, I think brass has a greater tendency to develop a leak from the different expansion rates.

I'll let you know how it works.

NOW, it looks like I still have a layer of gunk all on the interior of the cooling system, any ideas on how to remove it?

I may have to resort to some sort of chemical flush additive, then probably change out the water pump as good measure.
 
I'll usually do a heavy acid flush the first time I do it (that Prestone stuff with Oxalic acid and a neutraliser) and then just run a gallon or so of vinegar through it every other year afterwards. Make sure you get all the tap water out, and use either distilled or R/O filtered to replace it. Using tap water usually just craps the system up even worse, due to dissolved metals and solids...

5-90
 
I've used Distilled water for years.

My last couple of cars were near new (dealer demos, factory comp cars, etc.) so I got them with the OEM coolant fill. For those I never did a flush (not necessary) just drained the coolant (all of it), spent a little extra on a couple extra gallons of distilled water and fill and run the motor with distilled water, then fully drain again, and fill with 50/50 distilled water/anti-freeze. It was a flush, but no chemicals, just a flush with fresh distilled water. No need to use a chemical flush since there were no deposits and none were piling up since I was doing the proper preventative maintenance on the cooling system. My '91 Caravan at 11 years and 230k miles still had no deposits in the radiator or the engine cooling jackets as best I could tell.

I think it really helps to totally drain the old fluid and replace with new, using distilled water. I drain the radiator, then the block with the water jacket plug and then the heater core by pulling a heater hose and using either a wet/dry vac or compressed air to force the old fluid out of the heater core. A new pressure cap and thermostat ever couple of years really helps also.

In this case, I'm stuck, I'm going to have use the most powerful chemical flush/cleaner to the cooling system to get out all the gunk from the previous owner. I'll probably put the old radiator back in to do that, then install the new one once the cooling system is cleaned out.
 
Try the prestone 7 hour flush, I've had very good results with it.
 
Isn't the name of the product "Super Radiator Cleaner"? You leave it in the motor for 7 hours of operation, then drain and flush with fresh water and fill?
 
Could be, I've seen the name change a couple of times, used to 8 hour flush...might be that last hour cleaned too much out..I know the first time I used it I got a bit nervous, never saw the inside of my radiator that shiny before...looked like it has just been freshly soldered.
 
I found a 5/16" Square Key at my local ACE hardware store in the fastener section, only a dollar, which was cheaper than a 8mm hex wrench. It was about an inch long.

The plug was stubborn enough that it still twisted the key a bit, it finally broke free before the square key twisted in half.

I got the plug out and nothing came out, just some oily residue. I put it back and checked my haynes manual, which I cursed as being wrong, because I pulled the plug that it said and got nothing.

I went back and pull the plug again, poked a screwdriver in there, it took some force and a wall of crud broke and the water started flowing out.

I have got to find something to dissolve all this gunk, I'll be using the "Super Cleaner" hopefully that will work.

I haven't taken the plug to the hardware store yet to find the thread and size, I'll let you know when I do.
 
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