The Stovebolt Site Forums The Shop Area Engine Shop clogged 6 cyl engine coolant drain plug

hi.

looking for help on a clogged coolant drain plug on driver side of engine near the firewall.

mu question is how far 'into the engine' does that hole go before it might hit something 'solid'? does it branch off?

1957 3600.
6 cyl.

ok, so I have searched and read every thread here on stovebolt, and on other forums, about how this coolant drain plug area can get clogged. and also how critical it is for a successful engine coolant flush to get that drain open.

I have read various things that people say they have done - including giving up, or opening up the engine (which is not an option for me right now).

I have read various questions about this, but have not seen a real answer as to what are the dimensions of this drain hole? how far 'in' does it go before it hits something solid? does it branch off?

on the plus side, what I see on the end of my screwdriver after wiggling it in there is black and 'wet'. so, I am thinking if it is 'wet' I have a chance of clearing the hole since moisture is getting to the silt that is in there (kind of like a fine grade black sand).

any first hand experience would be appreciated.

thanks in advance

I had some fair results using a Garden Sprayer with a soapy water mix. Spraying into the drain holes. I did have the heads off however. You might try that with the Rad cap off. Fishing with a stiff,but bendable wire through the hole might work.

The water jacket goes all the way to the other side. Just forward of the hole you'll find a cylinder wall. A coat hanger wire works good. Scrape every where you can get with it.

Put your air nozzle against the hole-make sure the radiator cap is off-then give it a blast, alternate with inserted wire as said above, the dirt has to go somewhere, so, be aware of that.

Ed

Probing that one tiny hole won't be very effective at removing 50+ years' worth of crud that has accumulated all along the bottom of the water jacket. Even if you get coolant flowing freely from that one spot, how do you plan to handle the other areas? The only effective way to clean the water jacket is going to be by pulling the cylinder head and the freeze plugs, and doing a LOT of probing and scraping to dislodge the sediment all along the bottom of the block, not just near the drain plug.
Jerry

I just unplugged one the other day. I started out by wallering a small phillips screwdriver back in there. Then I used compressed air to finally unplug it. Once I got it to drain it kept clogging back up, so while I was continuing to flush I kept blowing compressed air back into the hole until I eventually got all the trash flushed out. I had both the freeze plugs on that side of the block knocked out at the same time. It helped aid the flushing. My block was almost half full of mud and scale. I got it all cleaned out.

thanks for all of the thoughtful replies.

but I am still not sure how 'deep' is that hole before it opens up into the engine itself? I just can't picture it.

for example, as i am scraping, about how far should I be able to get in there with a screwdriver before I hit something solid?

thanks in advance

the cylinder is right there about 1/2 to 3/4 inches. I use a coat hanger size wire and probe all over the place. Poke around until you get the clog free and then keep probing until clean water comes out. I've done several of them, and that's the only way I know how to do it with the engine in the truck and no plans to remove anything in the near future. Patience and fortitude!

If all one is able, or willing to do is clean the hole where the drain petcock is, one may as well not do anything at all. There is a huge area in the water jacket which will be packed with crud that you cannot access without tearing the engine down.
You may think that cleaning that small area to allow some water to come out is a good thing and therefore makes you feel like you have done something. I suggest that you instead would be giving yourself a false sense of security.
Since an engine which is loaded with crud likely has not been worked on for a very long time, you can just run it as is (as long as you don't have an overheating issue from a completely clogged water Jacket) until you decide to tear it down for a proper rebuild. Then you can actually clean that water jacket out.
Carl

one cannot argue with the logic behind these comments.

indeed, to do it the 'right way', and the most 'effective way', one must take apart the engine and clean it all out - the engine is 58 years old, and yes, it is dirty in there.

but sometimes, we are not able to do things the right way, even though we might want to. so, we feel that we have to try to do something that helps - even if it helps just a little. and that is my intent here - help just a little.

if I can spend some time with a hanger or screwdriver and get water flowing out of that hole I will feel that I accomplished something - even if it is just a little something that I accomplished.

if I can get water flowing out that drain hole, and flush the engine coolant from time to time (while maybe loosening up some of the other silt in there), then it is better (at least for me) than not doing anything at all.

unfortunately, I simply do not have the skills to open that engine, nor do I have the money right now.

so, I do understand that if I can indeed get it to start draining it is not the best it can be, but i can live with that for now - and that is ok.

thanks for the comments. I hope they help others as well in the future.

Gene

Gene,

You (and Deve) are correct.

Also, you understand the limitations of your techniques.

They are worth a try. If it does not work, you have to "dig deeper".

Future readers of this thread will understand that Carl and HrL and others are correct, IF the engine apart and variety of holes in the block are accessible.

Without seeing the truck or engine I can not say for certain how easy the access to the core plugs along the side of the block would be.

Though one should be able to remove those core plugs without removing the engine from the truck making it easier to clean out the water jacket.

Still not as effective as removing the engine and taking it apart and having the block boiled out.
Jeffrey

At least two plugs on manifold side - not easy to work around the exhaust manifold/pipes

At least one at the rear of the block - blocked by firewall (this/these are critical for a good clean interior

maybe one at front of block? - if so, it may be accessible

The earlier (1955nd and earlier) water pump can be removed to get at those holes in the front of the block - these are very small holes compared to 1955 and later blocks (with the water pump in the "wrong" position for good radiator cooling.

Yep thats right Tim. It is rarely a perfect world when you find this problem. Now that I have rebuilt these things countless times I just make sure the engine shop is clear about cleaning it out at rebuild time. When it's in the truck, a wire poking around is the most efficient/aggravating means to do it. It may not get it all, but it's far better than nothing.

When my engine shop prepped/tested my 1954 Hydra-Matic's 235 block, they called me so I could inspect the block cooling passages and inspect the (crack prone) 848 head.

With my other 235 block, I had to painstakingly try to clean out cooling passages via coolant drain-port, small water pump holes, and a few accessible block casting holes.

I may have missed it, but has anyone said anything about your radiator? I would recommend that you get that cleaned out as well. This topic came up not too long ago and someone was talking about a muriatic acid mixture. It sounded like something that was a little risky, but possible if done right. I am not going to sign up to try it, but is there anything else that could act as a solvent without damaging anything to clean the passages?

One of the reasons I am in the middle of rebuilding two engines right now is cracked heads and clogged radiators from sitting too long.

Gene, since the timing isn't right for you to tear down the engine at this time, and you aren't having overheating problems, and if you don't use the truck as a daily driver, you can get away with running it as is until its time to tear it down to make it like new. Poking a wire in the drain hole until something moist comes out will make you feel better. At one point for 18 years, I was in your shoes and vowed not to do anything until I did everything to it. Just keep an eye on the engine temperature gauge. Most of them don't run hotter than the "0" on the 180 mark.
Carl

If your block is full of crud - you need to get it all cleaned out. Remove the intake and exhaust manifold, knock out the freeze plugs on the side of the block and in the front under the water pump and get a garden hose with a good spray nozzle on it and a piece of wire coat hanger and wash it out. It's a very simple task - but you have to remove all of those parts in order to do it effectively. You cannot do it via the drain hole on the back of the block.

Gene, all comments made by others and you are completely correct. What is not known is how much crud is in the block.

I recently worked on a 235 that had been well taken care of for its entire life. When I flushed the system while the engine was still in the truck, the back plug was clogged. I did a little tinkering with a coat hanger and it began to flow freely almost immediately without any more black stuff in the mix as I finished the flushing.

If your engine was maintained throughout its life and flushed regularly including pulling the back plug, you might not have the deep crud build-up that others have experienced. You might be lucky!

As others have done, I changed out the back plug to a petcock to make draining easier in the future.

I use a shade tree mechanic's approach when flushing a block. You want to avoid getting any of the crud into the radiator or the heater core. Remove the radiator hoses and the heater hoses at the block/water pump. Remove the back plug. Pull the heater hose fittings from the thermostat housing and the water pump and plug with threaded plugs. Remove the thermostat. Insert your garden hose into the upper radiator hose fitting and pack it tight with a wet rag. (Keep this packed tight during the process to keep pressure in the system.) Turn your garden hose on full blast. Turn it on and off to pulse it. Occasionally kink the hose to let it build up pressure and then unkink it to surge water through the system. After doing this for a while, plug the lower radiator hose connection at the water pump with an expansion plug (a couple bucks from the plumbing section at Home Depot). Repeat the process with just the back plug removed. Then pull the expansion plug and let the system drain. Turn the engine over to let the water pump spit out any crud in the impeller before reattaching the heater hose and the lower radiator hose.

It is easier to do this with two people...one handling the hose and one keeping the hose in the thermostat housing with the rag packed tight.

A deep clean by pulling the freeze plugs would certainly be more thorough.

Good luck,

Matt