[Rup91]

Hello All!

After procrastinating for over a year and a half, I finally completed the dreaded spark plug swap. To my surprise, it was a lot easier than my friend’s E60 M5. My vehicle had been VERY sluggish lately and I realized that the spark plugs in place had probably around 40-50k miles. So on this very cool Houston day, I decide to swap them out. Most plugs seemed fine, however I did have 2 that literally had no gap, they were welded? together. I did also notice that on the passenger side, I had 2 heavily corroded coil packs and on the driver side just 1.

Now I have no knowledge as to how coil packs work, I just know that they are essential to the car. My question is, why are some heavily corroded and others very lightly corroded? Did something drip in there?

Given that my car is about to hit 65,000 miles, should I replace the corroded ones or just bite the bullet and replace them all? I put it all back together and she’s purring perfect. Performance is back, and she’s snappy as ever. If I do need to replace them, oem or aftermarket? I’m running stock with just aftermarket eventuri intakes; I intend to keep it this way. If I replace just the corroded ones, is it risky to mix aftermarket coil packs with oem? Any advice is appreciated!

[shawnhayes]

If these were from under the coolant tank, you have the dreaded (and occasionally motor fatal) coolant tank leak.

If that is the case, replace the tank IMMEDIATELY. More antifreeze dripping on there occasionally kills the engine.

Shawn

[Rup91]

Originally Posted by shawnhayes

If these were from under the coolant tank, you have the dreaded (and occasionally motor fatal) coolant tank leak.

If that is the case, replace the tank IMMEDIATELY. More antifreeze dripping on there occasionally kills the engine.

Shawn

I've already been a victim of that. There was a little bit of dried coolant that I noticed when I swapped them. What is interesting is that the opposite side had more corrosion than under the expansion tank side.

[shawnhayes]

Originally Posted by Rup91

I've already been a victim of that. There was a little bit of dried coolant that I noticed when I swapped them. What is interesting is that the opposite side had more corrosion than under the expansion tank side.

I have not. My understanding is that the expansion tank leak STARTS with the ones under it, and more can get the coolant on them. How in the heck it could make it from one side to the other is beyond me over a hot v, but that's what I'm told.

Maybe leftover from the failure?

Shawn

[hookson]

Maybe someone didn’t add coolant carefully enough and spilled it on those cylinders

[pbonsalb]

The coils have protective boots over the cavities they go in so theoretically they should not get wet. But in reality, they can. Could be condensation, could be water done how got past while washing the engine. I would not worry about a little surface rust on the coil bodies, but coils are relatively cheap so replace them if it makes you feel better.

What I found most interesting in the OP’s report was that the plug gap had diminished. It should get bigger. But the plugs seem to have something on them and I don’t know how to read it. Were they changed at 37k as scheduled?

[Oz M5]

"Very cool Houston Day"... I'm detecting a little sarcasm 😎.

[Rup91]

Originally Posted by pbonsalb

The coils have protective boots over the cavities they go in so theoretically they should not get wet. But in reality, they can. Could be condensation, could be water done how got past while washing the engine. I would not worry about a little surface rust on the coil bodies, but coils are relatively cheap so replace them if it makes you feel better.

What I found most interesting in the OP’s report was that the plug gap had diminished. It should get bigger. But the plugs seem to have something on them and I don’t know how to read it. Were they changed at 37k as scheduled?

I doubt they were changed at 37k miles. I bought it used with 40k miles, BMW dealer did not replace them based on the carfax.

I didn't realize how cheap these coils are. I will be replacing them with Dinan coil packs.

[hookson]

Originally Posted by Rup91

I doubt they were changed at 37k miles. I bought it used with 40k miles, BMW dealer did not replace them based on the carfax.

I didn't realize how cheap these coils are. I will be replacing them with Dinan coil packs.

I am thinking about them too. Although don’t have any reports of them on F90.

[shawnhayes]

Originally Posted by pbonsalb

What I found most interesting in the OP’s report was that the plug gap had diminished. It should get bigger. But the plugs seem to have something on them and I don’t know how to read it. Were they changed at 37k as scheduled?

Gap is closed by rust. Generally requires water in the cylinder to do it.

Shawn