Hey all,

I'm just coming off a left-side head gasket repair and am now having different issues than I was before.

BEFORE the head job, it had a constant misfire (spark plug wire burned through), and temperature fluctuations (rapid up/down, never overheated). I replaced the gasket, bolts, and had the head machined and inspected.

It ran great after the job, for about twenty miles. Then it slowly got hot at a red light, luckily the last one before home, so I parked it.

So now, AFTER the head job, it rough idles, continuous white smoke out the exhaust (it does NOT smell like fuel unfortunately), and there's now coolant in the oil (chocolate milk color). All of this in less than 50 miles.

Did a dry compression test and got 180 pounds out of 1, 3, 4, and 6. Cylinder 2 had 165, and 5 had 140. I then did a wet compression test on 5, and the pressure shot up to 180, which tells me something is bad in the lower engine. Given the coolant mixing with oil and I assume in the exhaust, sounds to me like it's a cracked cylinder wall.

The only thing I'm not sure of is that 40 lbs less compression doesn't seem like all that much, given how much coolant smoke seems to be in the exhaust. I'm also assuming that the overheating is from coolant consumption and not a lack of power at an idle. It only seems to creep up at a red light.

At this point I've pretty much counted the Ranger as a loss, but if anyone has any insight as to what exactly might be happening, I'd at least like to know.

Thanks in advance

 

Welcome to the forum

You could put a cooling system pressure tester on the rad cap opening
Disable spark or fuel
Then crank engine over
If you get a steady pulse of high pressure then its a head gasket leak or cracked head
Pull out one spark plug at a time and repeat test
When gauge stops bouncing then last spark plug removed is the leaking cylinder, replace spark plug to confirm
If gauge just reduces bouncing a bit then keep removing spark plugs, you have more than one leak point

Crack block would be way way down on the list for a 4.0l SOHC
Wet test can temporarily seal head gasket leak, this is more likely than sealing a block leak

Blown head gasket can breach an oil passage sending lots of coolant into the oil, and coolant from a head gasket leak will run down past the rings after engine is shut off because of the higher pressure in cooling system
The fact you see white smoke from tail pipe means coolant is for sure in a cylinder, not just in the oil

In any case both heads would need to come off so depending on your situation, replacing engine with used low miler may be better option
That's a judgement call on your part

 

Thanks for the info. I'll do that coolant pressure test tomorrow, but I'll probably go ahead and pull the head as well. Isn't there a type of dye or something to check for cracks in the head? I had it machined, but I'm not sure my machinist tested it further than the surface condition.
Kind of heartening to hear it might not be the block. I've done one head already, doing two more won't be so bad, as long as I don't screw it up again if that was what happened. I like my ranger and don't want to trash it, especially because it's my only set of wheels at the moment.
I'll post what I find tomorrow.