Hi Guys, I've been experiencing a strange problem, and wonder if any of you have seen something similar. As my engine warms up, the air that's trapped below the spark plug boots also becomes warmer and it expands. On two cylinders (1 and 3) the pressure is sufficiently strong that it pushes the rubber spark plug boot upwards. In the past this hasn't really been a problem, but I just replaced my ignition wires and the force of the "trying to escape" plug boots is now sufficiently strong that it's actually popping the plug wires (on 1 and 3) off the end of the extenders. Okay, so you're probably thinking that I should crimp the connectors on 1 and 3 a little bit to see if that stops the wires from popping off, but what I'd really like to know is why this is happening and if anybody else has experienced anything similar. It's really annoying -- thus far I've managed to lose two of the rubber boots this way. For what it's worth, it's surprising how well the engine runs with the plug wires for 1 and 3 disconnected!!!!! I suppose one fix might be to lightly glue the offending boots onto the extenders. Comments, opinions, thoughts? Thanks.
I wondered about that also, but the plugs in question are torqued correctly, and this has been a problem that I've had forever (especially on number 1).
What 2NA said, sounds like a loose spark plug. You should be able to "feel" the looseness in the extender.
Yeah, I know, it's what I thought too, but they aren't loose. Perhaps I just need to replaced the two plugs in question so that I know with certainty that they have new crush washers. This is a new one on me however -- I thought that plugs could be installed over and over again without having to worry about the crush washers ... is this not so?
Perhaps you can put your hand over the spark plug hole with boot and extender removed (but spark plug torqued in the hole), on a cold engine running and feel if there is pressure. not sure if a head gasket leak around this area will result in an air leak.
I'm assuming you have the correct boots for your model, the upside down cups that mount onto the extender. (IIRC, The red QV style boots have a small vent hole that prevents this problem.) First, eliminate spark plug sealing as a problem. In theory you should use new crush washers each time you pull the plugs out. The old style Cu sparkplug washers always needed replacing or annealing. However, if they're Al washers, I've always reused them w/o leakage problems. It's rare, but I've heard of plugs that leaked because the seal between the ceramic body & the metal base had cracked. Replacing the plugs would correct that as well.
There's a little vent hole in the rubber "umbrella" spark plug boot, or at least there's suppposed to be one. Is it there?, or is it plugged?
I had the same problem a few of years ago with my former '84 Mondial QV. I bought wires and caps from Magnacore and installed them. The caps fit very tightly on the wires and into the holes. As the engine heated up, the pressure was enough to pop the caps. The old caps fit rather loosely in the holes, so pressure wasn't a problem. I used a leather punch and put a very small hole in each of the caps and no more popping problem. There was no issue of spark plug blow-by -- new plugs, new washers, properly torqued. It was just pressure buildup because the caps fit so tightly. Consider the small hole fix. It doesn't take much of a hole to relieve the pressure.
My car's using the boots that fit deep into the hole (i.e., the boot on the left with 4 ridges around it). Because of the design, it's actually quite difficult to get a hole punch into the groove at the base of the boot. I tried before, but will give it another try. I think it's being suggested that I might be better off using the domed boots to the right ... correct? Image Unavailable, Please Login Image Unavailable, Please Login
The domed boot on the right requires the stand tube molded in the head. Unless it is a very late 77 you will need the type on the left. Punching a hole in the left ones will assure you water in the plug valley as Tex stated. Even new boots do not seal well enough to consistantly keep the water out..... deal with the SOURCE of the problem, fix the compession leakage. Its also a possibility that you already have water in the holes and it is the resulting steam that is pushing the boots out.
Well, this is what I found. I always tighten my plugs by hand, without a torque wrench. I've done this since I was a "kid" tinkering on my various motorcycles. I do this by feel and am particularly wary about the risk of damaging any of the aluminum threads in the heads. I thought the plugs were in nice and tight, but when I put a toque wrench on ... well ... that was a different story. At 14 ft lb I could not believe how much more they tightened up. In fact, I was scared that 14 ft lb was too much, so despite what the 308 owner's manual says, I backed my torque setting off to 12 ft lb. Anyway, every plug tightened up quite a bit, and needless to say, the plug boot problem has now completely disappeared. I'm curious to know how many fellow fchatters tighten their plugs by feel and how many use a torque wrench ... let's do a quick poll.
'81 308: Cylinders 1-4: Torque Wrench Cylinders 5-8: By Feel. (Cannot get a torque wrench back there unless I take off the rear deck [ain't happenin'])
I know what you mean. I was lucky enough to have my engine cover off so it was relatively easy to get a torque wrench onto them.
I tighten plugs by feel too. But I do occasionally check my feel against a torque wrench. Tighten something to the specified torque and try to mimic it by loosening and retightening the same amount (wrench angle) and double checking against the TW. Once you have the feel youll be okay. I dont see any reason a short "click style" inch pound TW wouldnt work on the front bank if your concerned about reaching proper torque. I find plenty of room working over the top of the open deck lid.
It's a little bit like having "the force"!!!! In all seriousness, I'd never checked my "by feel setting" against my torque wrench set to 14 ft lb. I was really surprised by just how "tight" 14 ft lb really is. Without this confirmation, I would never have had the courage to manually apply so much tightening torque as my gut would have told me that I was probably stripping threads.
