Can I use PB Blaster to loosen spark plugs

Last Saturday I went to replace my spark plugs. When I got to #3 I found that I would have need far to much torque to get the plug out. I would have had to use a breaker bar. It started to make that noise, if you know what I mean, the noise of something is going to break. So I just put the coil back on and moved forward.

The same thing happened to #4 and so I moved on.

#5 hose went fine.

I am thinking of giving another attempt but this time I'll spray some penetrant down the hole and leave it soak for a while.

Good idea? I'm really not into having the threads come out with the plug or breaking the plug.

IF I am on a dangerous path, I'd rather just let those two remain in place and just keep the two overly expensive Volvo spark plugs rest in the cabinet.

This might be due to an engine overheat, did that on an old 740 , after blowing steam the plugs were very difficult to extract. Do it slowly, let the penetrant work.

I had the same issue here when I first got my 850.

The others are right, avoid the breaker bar.. very risky to get too aggressive.
If you can budge the plug, work it back and forth to help a small amount
of Mystery Oil (my favorite) penetrate better. Don't over-do it with the
penetrating oil, you only need a little for the threads, and more just makes a mess.

In my case, I needed to cleanup/retap the sparkplug holes, which brings up
another problem of not wanting metal chips in the cylinder/valves etc.
I was lucky to borrow a real tap from a local garage,
(there's another thread cleaner gizmo cheapo tool that I saw at another garage, that is a piece of junk.)
I put a lot of wheel brg. grease on the tap to catch the chips, and it worked OK.
If there were any chips in there, I suppose they were small enough to
blow out the exhaust.

I used Never-Seez on the new plugs, and that worked fine.
I needed to retap the threads for the plug cover too, those steel Torx head
screws were also seized up in the aluminum head, they need Never-Seez too.

Later I used that same tap to cleanup the threads for the O2 sensors, so that's
a good tool to have!

Good luck, Bill

PS: While you have the Mystery oil out, put some on the thermostat cover screws,
there's another problem location with steel screws in aluminum.

You use MMO as a penetrant. Never used it for that but used it in engines.

Just thinking out loud here but I could imagine liquid nitrogen maybe shrinking that plug - also some kind of long-term vibration/jackhammer force might 'break' the connection between the two metals. Maybe a little solenoid attached to a spark plug socket jackhammering for a few days with that penetrating fluid seeping in.

Hi again,

Is the plug completely frozen in place?
I'd forget liquid nitrogen.

There's elements of judgement and risk with problems like this.
Did you try the overnight MMO soak and it still wont budge?

You could try a 3/8 Breaker bar and give it some medium sharp taps with a medium
ball peen hammer. If it moves a little, tap it back. See if you can
get some easy motion back and forth. put it where its free the most and give a
few drops of MMO, then go at it again. What's wrong is the threads are Galled,
and you have just what I had. You'll need to tap the plug holes afterwards.

Just hope you don't snap off the plugs in the head. That's ugly, but so is where you are now, since there was never any anti seize grease applied.

Have at it, Bill

I have not done anything except spray PB blaster in there and that was weeks ago. The risk / reward is not good. A lot of risk with minimal reward.

Both plugs did start to turn, just a bit (not even an 1/8 turn) but they both reached a point that they stopped. I then tightened them back in and left it alone.

BIgger fish to fix like the geartronic rocker that broke and now if you just touch the shifter the shaft will slip over into manual shift. It is ok as long as nothing touches the shifter.

It is a $12 item and 1.5 > 2 hours labor.

"... I could imagine liquid nitrogen maybe shrinking that plug..."

Man, you read my mind. I just couldn't think of an easy source. My dermatologist came to mind. He has a handy-dandy spray can of it ready to attack me every time I go in for a check-up.
--
Current rides: 2005 Volvo S80 2.5T, 2003 Volvo V70 2.4NA, 1973 Volvo 1800ES (getting ever closer to road worthiness)

Yes I've tried everything and MMO is my favorite. One time I soaked the rings
in a Toyota that was sitting around for a long time and became a huge oil guzzler.
a 24 hr soak fixed the stuck rings and it went back to normal.

MMO and Never-Seez are your friends. :-)

From a Paul Brand newspaper article:
"By the way, Frost also suggests a trick that may remove the old spark plug without damage. Apply a good penetrant like Deep Creep and run the engine up to full temperature before trying to unscrew the plug. The aluminum cylinder head will expand more than the steel body of the spark plug. If you're lucky, the plug may come out without significant damage to the threads in the cylinder head."

But, if the head is really hot, the aluminum will be softer and easier to destroy. So, pour a bunch of penetrant in the plug hole, run the engine, let it cool, check the level of the penetrant and let it sit overnight...
--
Keeping it running is better than buying new

I agree with warming up the engine and that should allow the penetrant to seep down. I also agree that removing a plug from an engine is a no no. I never do such a thing and I am so anal about it I only change the plugs in an aluminum head only after the car sat overnight.

Did you ever get that spark plug out of your Tardis?
--
Keeping it running is better than buying new

Go ahead and dump a bunch of PBBlaster in the hole, it will not hurt anything. Sounds like the PO didn't use any anti-sieze, and the plugs were in there over 50K miles.

I agree, using a breaker bar is not a good idea.
--
Keeping it running is better than buying new

I don't see where it would hurt to try. I just don't know how well the penetrant will be able to seep past the seal and down and into the threads. Maybe if you let it soak for a couple days through a few engine temperature cycles. If you were already able to loosen them even a couple degrees, you might find it helps to tighten them just a very very tiny bit like only about 1/2" out at the end of the breaker bar, then loosen about the same amount. Work the breaker back and forth the tiniest bit until it loosens enough to start increasing the counterclockwise stroke.
--
Current rides: 2005 Volvo S80 2.5T, 2003 Volvo V70 2.4NA, 1973 Volvo 1800ES (fixed the ignition - now back to the brakes again)

The day I was working on the car I tried the re-tighten trick but it didn't work.

When trying to remove it reached a point that turning wasn't happening and I really didn't want to use a breaker bar.

Never had any plugs that were this tight. I think the previous plug installer didn't understand correctly torquing the plugs.