Do I have a cracked head on my 4.0 1999 Ranger
Sooooooooo, about 6 months ago I started getting a rough idle in my 1999 4.0 x cab 2 wheel drive Ranger (135,000 mi). It also began to feel like a miss throughout the RPM range. I was messing around under the hood and noticed I was low on coolant so I added some and walked back around the drivers side to goof around with plugs wires, etc. I noticed coolant seeping out of the drivers side front of the engine. Well even though Im no mechanic, I decided that was a bad thing!
My brother and I replaced the head gaskets (both sides). We took our time, did a good job of cleaning surfaces, etc. I say this so that you realize we did a pretty decent job and didn't drop beer cans down the cylinders, etc. I did however cut one important corner. This vehicle is my only car, so I checked the heads as well as I could visually (laid a straight edge against them, etc.) I did not observe any cracks, warps, etc.
We got it all buttoned up and drove away. Same missfire type condition!!!! I looked at the plugs. Drivers side front or middle plug(cant remember) looked funny(right where the head had been leaking), so I replaced it.
The truck ran like a champ!!!I was very happy. I figured the plug was just previously damaged from the leak and the replacement fixed it.
Over the next month it started showing the same condition little by little, grrrrrrrr! I have a very short commute and don't drive it a lot. Check Engine light comes on. Its an o2 sensor. Downstream and yes on the drivers side. I replace it, and it runs normal. I pass my communist emissions test and over the next few weeks the miss fire/ rough idle comes back. I should also mention that every time it shows up, its much worse when the engine is cold, as it warms it smooths out but not completely.
Today I pull out all of the plugs. Passenger side look normal. All three drivers side are very clean and have a reddish hue of light rust on the treads. Especially toward the electrode end. Im starting to think the is a cracked head on the drivers side ( the side of the original leak).
I then checked the compression to see if it was lower on the drivers side. From the fire wall forward the drivers side showed 120, 130, 120. From the firewall forward the passenger side showed 150, 140, 140.
All this confirms to me that its probably a cracked head. The problem is I really dont know much about cars, diagnosis, etc. I can do brakes, oil changes, etc. but my skills are limited.
Am I barking up the right tree here?????? HELP!!!
Is there any other test I can do???
I dont want to spent two days replacing a head and not fix it!!
Thank you in advance for your help