I recently switched to Bosch Platinium plugs on my '92 460. I tightened them pretty snug (didn't use a torque wrench). After about 20K mi I started noticing what sounded like an exhaust leak. After checking around I found that several of my plugs had loosened. I re-tightened them and the noise problem was resolved. I've changed my plugs several times in the past and have never had this problem with convetional plugs. Is this a common problem with this model Bosch plugs?

 

I'm running the Bosch Platinum + plugs and they are great, never a problem

John F.

 

You need to be careful with the Bosch platinum plugs. The white ceramic insulator is thinner(and weaker) than most plugs and mechanics are finding that they break off and fall into the cylinder and do major engine damage. This most likely is from detonation. I didnt find this out until I installed a set in my E-350 RV. It's such a pain to change them Im takin the chance but runnin high octane and taking measures to make sure it doesnt ping. I'll change em in the Spring. Spark plugs coming loose is a particular problem with Fords. Go to Timesert.com and you can see special kits just for Ford plug problems. I'll do a little research and repost if I can find the exact nature of the problem.

 

T18Skyguy-Thanks a lot for the heads-up on the Bosch plugs. That's the first I've heard of it.

 

A loose spark plug is more serious than it looks. When a plug is loose it cannot transfer heat to the cylinder head the way it should. This cause's it to overheat and the plug itself becomes a source of pre-ignition and detonation. Then because it's loose, it allows the piston to suck fresh air around the plug which leans the mixture and brings on more detonation(very high heat) and has been known to burn holes in pistons and blast out the center of the plug. Note that plugs are put together with heat and thats the way they come apart too.
The reason the plugs get loose is a buildup of carbon in the threads of the head. Oxygenated fuels form 5x as much carbon as normal fuels. With people running their plugs longer extra carbon deposits in the threads are greater. Cleaning the threads(called chasing them) with a plug chaser is a good idea. A good indicator of a problem is if you cant seat the plugs with your fingers or if the gasket on the plug you removed is not completely crushed. If this problem exits, you may think you torqued the plug right but you only jammed it in the carbon. One helpful thing is try and stick to plugs that have their threads rolled not cut. NGK is good-they have plated threads. Threads that are rolled are stronger and easier on the cylinder head. Another thing you can do is after you chase the threads, put a very small amount of high temp antiseize on the first 2 threads of the plug. I cant emphasize enough that is must be a small amount-too much is worse than none at all. thats all-gotta go to bed.

 

honestly the bosch spark plugs are a lot of hype the amount of platinum that is used on them would take a microscope, and micro scale to find and measure. For platinum plugs the only true platinum are ngk, and they are pretty expensive. I have done a lot of reading and researching on them and they don't provide any performance gain, and infact may cause a slight (this is ever so slight as in you will have to have a dyno to measure it but it's there) decrease in power, the only advantage in them is that they last longer which in applications that the plugs are extremely hard to get to this is a definate advantage, but things like the splitfire, and bosch platinum plus 4 are just marketing techniques to pry more money out of your wallet. for performance stuff go look at the race teams and see what they are running, and in honestly even the ones sponsered by bosch aren't running bosch plugs, and non of them run the platinum plugs that I can see with the exception of some of the serious endurace types of racing and then only the NGKs.
I am not telling you what to do but I will tell you do a little researching on the hype, I did, and I don't run those on my race truck or for that matter on my daily driver that is gas powered I have switched to autolight racing plugs in the race engine and have absolutly no problems were as with the bosch that I tried they lasted 5 races or approx 50-60 passes and the autolights I just pulled out lasted all season (around 85 passes) and still look new, I will change them but the bosch looked like they had been burnt with a torch.

 

platinum plugs are only needed in waste spark ignition systems like the newer fords. for you regular copper core autolites or motocraft plugs will work.

 

Autolites are a good plug and will hold a gap longer than a Champion. Champions are made of softer metal which burns away quicker. There was a period of time years ago when mechanics stopped useing Champions cause of the problems. Champion then redesigned the plug but had to give them away for free to get the mechanics to start useing them again. Since were talking about plug problems, the guys with the newer 5.4's with the long reach plugs are finding that they seize and break off and the heads will sometimes have to be removed.

 

Well after reading all the points made here, I put in a new set of Bosch Platinums (single type) after cleaning the threads in the holes. Extended plug life and high operating temps (I tow heavy loads) are a major factors. The Bosch Platinums that I took out had about 50K on them and they were very clean, showing no noticable carbon deposits on the electrodes. I torqued them to about 22 Nm (manual calls for 20 Nm) taking into consideration that there was likely carbon on the face of the seats as suggested by T18Skyguy. The only unusual thing I noticed was a film of oil deposited on the ceramic base portion of the plug outside the threaded area. That might have come from the dilectric grease on the plug wires. I can't thank you all enough for the help.

 

Like Monsterbaby said Platnium plug lose power(Junk espically in fords weak igintion system). No platniums don't work better in waste spark systems, coppers just have half the life in that system. The resitence to spark is so great you can not use them in a CD iginition system. If u want a long lasting plug use iridium at 7-19 dollars a pop. I use them in all my cars. Also check your heat range. My 87 F250 calls for a heat range of 4(very hot) so I went one step colder with a 5 Part # NGK 7177 buy them from summit racing for 7 dollars.

 

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Thats great if you can afford to pay 80+ bucks each time you change your plugs.....for a racing motor i can see putting out that much coin for some...but personally i have used bosch platinums for years without any problems at all, except for one time i got 2 dead plugs right out of the box...but other than that they have worked great for my 460, and i used this truck everyday for work hauling a 16foot trailor with a ditchwitch, 2000 feet of conduit and ladders and tools on it.....now granted i change my plugs every year, not because they are bad but its just the spring maintainance i do every year....

 

I want to point out regarding my post about the Platinums breaking that it is not a common problem but it does happen on occasion.

 

SwOkcOffRoader I used to run them but for only 80 and I won't even second guess that they will run 100 thousand miles. All I can say is try NGK 2771 for 1.99 at a CSK(kragen) store. Don't tell them what you want them for, just the part number (NGK 2771). I gaurentee better throttle resonse, easier startups and possible better MPG. They don't tell you a good copper plug only last 5000 miles. The longer a copper plug last the more resistence it has. NGK has 5-6 thousand ohms. On the other hand a set of champions that I checked had 25-40 thousand ohms.