When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I was in the process of changing my spark plugs when upon pulling out one of the plugs I compared old to new. The old one is shorter than the new one. Is this normal? Or did the previous owner put the wrong plugs in?
I have confirmed the new plugs are the correct ones from the dealership and I cross referenced the part number from a DIY spark plug post on here.
It's worth noting that I have had no problems with the old spark plugs I just figured now is the time to change them out.
Whatever PO had in there is the wrong plug. Be careful threading the new ones in as Carbon has likely built up on the threads and will cause you issues seating them properly. I.E they may feel tight but they are not as the threads are binding. If you happen to have metric plug chaser (like a tap), now would be good time to use it as those threads need cleaned.
Options are: Denso #4705, IKBH20TT gaped at 0.044" << these are half the cost but need the gap corrected.
Whatever PO had in there is the wrong plug. Be careful threading the new ones in as Carbon has likely built up on the threads and will cause you issues seating them properly. I.E they may feel tight but they are not as the threads are binding. If you happen to have metric plug chaser (like a tap), now would be good time to use it as those threads need cleaned.
Options are: Denso #4705, IKBH20TT gaped at 0.044" << these are half the cost but need the gap corrected.
OEM PN: 90919-01249, FK20HBR11
I have never used a thread chaser before. I looked on amazon there is quite a selection on there. Is there a specific one (size) I should be looking for?
I have never used a thread chaser before. I looked on amazon there is quite a selection on there. Is there a specific one (size) I should be looking for?
You would want the chase to be the diameter and pitch as the existing plug threads.
Looking at the denso site shows 14mm x 1.25mm pitch.
One downside about chasing these threads is the carbon removed will drop into the cylinder. This will happen regardless of the method. It should blow out the exhaust harmlessly....
One option that couldn't hurt is to have a vacuum cleaner sucking up while chasing but that hole is deep. Doubt it will help.
Lay the threads of the old plugs into the threads of the new plugs. Do they lay seamlessly together? If so, then they're the same thread and pitch; so there will not be any cross-threading. However, like others mentioned, there is the possibility of build-up on the threads within the head that will make it tough to install. Personally, I'd put anti-seize on the plug's threads and try to install one and see how it works out.
FYI, you can make a thread chaser out of a correct pitch bolt with 2 sides ground off.
Using a lube like beeswax, boelube, or even just motor oil will help avoid galls, and back up occasionally like a tap. This isn't the place to apply all the ugga-duggas you got.
I would never do this to my cylinder head but a cut off disc can make 4 nice longitudinal cutting groves in the threads that will clear debris like this. That said our high detergent friend ATF applied to the plug/bolt wouldn't be the worst thing ever during carbon busting.
The main take away here is that if you've been wrenching for while and know the feel of things binding vs things seating properly you will be fine and take the required action. If you simply apply a torque wrench and quit turning when it clicks you could be in trouble when the plugs try to remove themselves from the head from not being seated properly.
2007 is350 spark plug change help
