1969 L36 Engine Coolant Drain

[Michael C.]

I've finally got my new DeWitts radiator and Mock water pump installed. Began efforts to drain the engine block coolant by removing the right side drain plug (what a bear). No coolant came out after getting the plug out. The photo shows some of the "crud" I dug out of the plug hole with a screw driver and ice pick. After penetrating about 1.25" into the hole, I apparently reached the far side of the coolant passage. Still no coolant. Is this an indication of major blockages in the coolant passages? Any suggestions?

I started this project about 6 months ago, so the I've had air in the coolant system all this time. This all started with a radiator that had "minor" seepage. No overheating issue that I was aware of (at least to the according to the temp gauge).

I haven't been able to remove the left side drain plug yet, so I don't know what's behind it. I'm praying that the PB Blaster penetrating oil will do the trick within a day or so. Of course this plug is harder to access than the right side. I was able to get a socket on the hex head, but it quickly began to round off. Any tips?

Because I didn't appear to have any overheating, should I just install a new left side plug, refill with new coolant and hope for the best?

Thanks all,
Mike

[Joe L.]

Re: 1969 L36 Engine Coolant Drain

I've finally got my new DeWitts radiator and Mock water pump installed. Began efforts to drain the engine block coolant by removing the right side drain plug (what a bear). No coolant came out after getting the plug out. The photo shows some of the "crud" I dug out of the plug hole with a screw driver and ice pick. After penetrating about 1.25" into the hole, I apparently reached the far side of the coolant passage. Still no coolant. Is this an indication of major blockages in the coolant passages? Any suggestions?

I started this project about 6 months ago, so the I've had air in the coolant system all this time. This all started with a radiator that had "minor" seepage. No overheating issue that I was aware of (at least to the according to the temp gauge).

I haven't been able to remove the left side drain plug yet, so I don't know what's behind it. I'm praying that the PB Blaster penetrating oil will do the trick within a day or so. Of course this plug is harder to access than the right side. I was able to get a socket on the hex head, but it quickly began to round off. Any tips?

Because I didn't appear to have any overheating, should I just install a new left side plug, refill with new coolant and hope for the best?

Thanks all,
Mike

Mike------

The block side drain plugs can be a BEAR to get out; they're often frozen solid. I'd look for a good 6 point socket; DO NOT use a 12 point. By a good 6 point socket I mean something like a Snap-On which is manufactured to close tolerances.

The failure of any coolant to flow from the side you did get the drain plug out is a bad sign unless there is no coolant in the block to begin with. That's unlikely, though, I'm afraid. It's easy to test. Just add water to the engine at the thermostat orifice in the intake manifold. If no water flows out the drain, you've got a problem.

Since you didn't have any overheating problems before you started this project, you could just do as you say. Button it up and hope for the best. I'd be very leery of doing that, though.

By the way, when you re-install the block drain plugs, use new plugs and coat the threads with anti-sieze compound.

[Edward J.]

Re: 1969 L36 Engine Coolant Drain

Mike, over the years the crude has settled at the bottom of the block, Just take a coat hanger and dig through the crude, coolant will likely be there. leave the drain plugs out and flush the block once you clean them out(Leave the themostat and housing off when flushing). I have seen this many time before.

[Michael C.]

Re: 1969 L36 Engine Coolant Drain

Thanks Joe and Edward for the tips/info.

I'll hunt for a 6 pt socket. Might be too late for that, considering I've already rounded the corners a bit.

I poured about a gallon of water into the thermostat opening, but nothing came through the plug hole. I used a rubber toilet tank stopper to seal the thermostat opening and blew air through a hole in the stopper...thinking/hoping a small amount of pressure might open the drain hole. Again, no luck.

I had already showered for the night before reading your tips, so tomorrow I'll climb back under the car to try cleaning out the drain hole mechanically. Should I risk pressurizing from the drain hole?

How about Drain-O? Just kiddin...

[Patrick H.]

Re: 1969 L36 Engine Coolant Drain

You'll probably just need to wiggle something around for a while and it will open up.
I used brass plugs when I replaced them on my driver cars. No problems rusting in place now.

[Terry M.]

Re: 1969 L36 Engine Coolant Drain

Joe is absolutely right about the tool needed for this task. Snap-on's motto is: "There IS a difference." and there is. I found a NEW Snap-on socket helped a lot. Sockets do wear and the fit is lost. IIRC I was able to use a flex impact 6-point socket on the left side with an extension and the 1/2-inch impact. All those parts have to be new or relatively new for the impacts to work. The flex socket and extension each have some play that diminishes the effectiveness of the impact. So in this case less is better. You may need to remove the engine mount to get good access. As difficult as that is, it will be worth your time to do it.

Bend the coat hanger about an inch or two from the end so it works toward the front and rear and top of the coolant cavity. You really want to get that crud (highly technical term there) out because it will make hot spots in your cylinder case.

[Michael C.]

Re: 1969 L36 Engine Coolant Drain

Thanks for the specifics Terry. I see on the Snap-on website that they have a "Socket, Impact, Shallow, Swivel, 9/16", 6-Point" as shown in the attached. Is that what you used? Hopefully I can find a good one I can borrow. Lists for $49.75. Ugh! Sears shows one for $36.99, made by SK.

The thought of having to remove the engine mount entered my mind and I shuttered. I remember the dealer replacing the mounts due to a "recall" when the car was only a year or so old. I believe they're somewhat bulkier than the original. All the more fun.

[Terry M.]

Re: 1969 L36 Engine Coolant Drain

Thanks for the specifics Terry. I see on the Snap-on website that they have a "Socket, Impact, Shallow, Swivel, 9/16", 6-Point" as shown in the attached. Is that what you used? Hopefully I can find a good one I can borrow. Lists for $49.75. Ugh! Sears shows one for $36.99, made by SK.

The thought of having to remove the engine mount entered my mind and I shuttered. I remember the dealer replacing the mounts due to a "recall" when the car was only a year or so old. I believe they're somewhat bulkier than the original. All the more fun.

Yes, the image you posted is the tool I used. As you can see the diameter is a little bulky; thus the suggestion of the possible need to remove the engine mount. The straighter shot you can get to the plug the better your chances.

[Patrick H.]

Re: 1969 L36 Engine Coolant Drain

If you don't have excessive amount of concerns regarding the engine paint you can use a bit of heat as well to try and get out the plug. That worked for me on one occasion.

[Michael C.]

Re: 1969 L36 Engine Coolant Drain

Well guys, I'm about to throw in the towel. I've not been able to get a flow of coolant/water from the right side drain. I've dug out about a teaspoon of BLACK crud/gunk/paste, but no liquid - other than a few drops overnight. Getting desperate, I was able to rig some air hose fittings to the drain hole to apply a bit of air pressure. I could hear a little gurgling in the block, and the water at the thermostat opening would move a little, but still no flow. The black stuff is about the consistency of thickened toothpaste or chunky peanut butter (with black peanuts). When I originally drained the radiator for removal there were no signs of oil. Any ideas?

Given the fact that I can clear this blockage, and the likelihood that the black mystery crud is blocking coolant passages, and the fact that my first attempts to remove the left side drain plug had bombed, I'm leaning heavily towards towing the car to a highly regarded shop.

[Joe T.]

Re: 1969 L36 Engine Coolant Drain

I know this is an old thread, but if you haven't corrected the problem yet, why not put a commercial flush product in and run the engine up to operating temp with the plug out and the cap on? That pressure and heat may push out what ever is stuck in there? regarrds...joe