jpc647

So I'm hoping to install a new radiator in the coming weeks, and I plan to flush out the motor. But the problem is, even after repeaded spraying of the plugs, I can get either of the drain plugs out of the motor. The passenger side is obviously easier to get at, but they won't budge. I even ran the motor up to temp, and tried to remove it hot, no dice.

I'm afraid I'm going to snap the head and then be royally screwed. Are there any tricks to getting these out?

Is there a good way to flush the motor without removing these two plugs? I don't expect the motor to be overly dirty, I've had the intake off, and everything looked clean, but it wouldn't hurt. I planned on using a flush chemical, running the car a couple of hours, and draining it, then flushing the block until clear water came out.

oldcutlass

I've never removed the plugs to flush an engine in the car. I just use a Prestone flush kit and follow the directions.

olds 307 and 403

Try some heat with a propane torch, a long rachet and a good 9/16" or 14mm socket, 14mm is a tighter fit. I find I have to crawl under the car if they are really tight to loosen them off.

classicmuscle442

Use of a six point socket would help, I would soak several times and use tooth brush style wire brush to clean.

oddball

+1 heat and a really good fitting tool.

MDchanic

It'll come. Sometimes they're TIGHT.

If it's that tight, I'd try pretty hard to take it off, just to be sure that the reason it's tight isn't tons of accumulated crud right behind it.

Either way, once it's out, I'd recommend scraping and digging all around inside, everywhere you can reach, with a coat hanger or similar, to dislodge all you can.

- Eric

Ozzie

Eric is right; the crud tends to accumulate at the bottom of the water jacket. If you don't have the block drains open it just stays there. The last one I did was a 460 Ford from 1976. It had Allen plugs, and was a real task. I ended up drilling out the plugs, cleaning up the threads, and installing ball valves. Now it's possible to do a real flush & drain. It would probably help if the manufacturers would use some anti-seize on the original installation.

jpc647

Thanks for the tips. I do have a small map gas(i think) torch, but I'll have to pull the car out to do that. I've been spraying it the last couple of days. I may give it one more try tomorrow, and if it doesn't work, I'll heat up the block around the plug with the torch and see if it helps.

Thanks!

Ozzie

It's O.K. to try, but if there is coolant in the water jacket behind the place you are heating, the effect will be drastically reduced as much of the heat will be dissipated in the liquid. Heating the block and cooling the plug may cause it to release.

allyolds68

This are what are used on boats that are raw water cooled that have to be drained every year to be winterized. They never get stuck

dualquadpete

You may have to use a "long' Johnson bar handle to get enough leverage to "crack' it loose!!! Regular ratchet won't do it!!!! Had this problem with friend's 70 Cutlass with 455 in it when he visited me from West Virginia and car was running hot!!! couldn't budge it with ratchet, put Johnson bar on with 6 point socket, did the trick, flushed out "Sludge" in system with rad flush.

m371961

I put petcock drain valves in. I personally do not like hanging a ball valve out like that, but most likely not a problem.

jpc647

I finally got them out!

I kept soaking them, and even put some penetrating oil in a little cup and taped it to the block so it would sit overnight.

And they came out.

Disappointingly enough though, there's no crud in the holes. I put a coat hanger in there and nothing comes out. It's too small for my finger, but there's certainly not big chunks of debris. Seems like all the effort was for not. But at least I got them out. I'll certainly be never-seizing them to put them back in.

Although, given the cleaness of the motor, both the water jackets and what I saw with the intake off. It's either a low miles motor, or someone did a rebuild, albeit, stock. :/

MDchanic

Now you can feel secure, though.

If you want, you can put some acid in there for a few days (just to the level of the plugs) and be sure it's clean.

If not, a at least you can give it a real good flush now.

​​​​​​​- Eric

jpc647

I think I'm just going to run some water through. tomorrow looks to be in the 40's. I'll roll the car out, run the hose through it for a few minutes to make sure and button it back up.

oldcutlass

Have you tried using an engine flush, or muriatic acid?

classicmuscle442

Would you guys bypass radiator to keep rust/acid out it while flushing and remove thermostat?

MDchanic

Typically, a flush includes the radiator, as you want to reduce corrosion and obstructions there, too, but you have to tailor what you're doing to what you're doing it to.

There is no need to remove the thermostat, as you will have good coolant flow once the engine warms up.

If you are flushing or cleaning the whole system, then you should use a purpose-made cooling system flush, or maybe vinegar or citric acid, as others have described.

If you are able to isolate the block (ie: just the block, with no exposure of water pump, head gaskets, etc.), you can use a stronger acid, such as muriatic (hydrochloric), phosphoric, etc., and can leave it in place for a good long time (days, potentially).

- Eric

jpc647

Yeah, I did a flush last year with two bottles of the Prestone flush. Left it in there a few days and 350 miles.

I'm just replacing the radiator, and I wanted to remove the drain plugs in the block just for assurance. I'll run some warm water into the motor through the thermostat hole and let it drain out the drain holes, but I'm not going to install the new radiator and then reflush flush the system. Besides, it's only around 40* during the day, and it's already pretty clean. It kinda seems like a lot of work for nothing.