Not good

So I took the car out last Sunday for a drive because it was a sunny day, if you lived in No CA you would know we have been getting rain up the ying yang here, parking back home after the drive, I notice wet spots on the incline of the drive way, so went and check coolant system and all good. car has been running perfect and no F.C.. so during the week I knew I didn't have the right adapter for my Stant press. checker and after verifying with Ashia the right # for the fittings to press check the coolant system and coolant cap, I ordered them and got them in 2 days, So the next sunny day I wanted to press check both the system and cap, that was Sat. beautiful sunny day, got the car up in the air and remove the bottom panels and pressurize the coolant system to 15 psi knowing the system runs at 18.85. great it held at 15 psi for .5 hr., went ahead a test the cap, it failed by not holding at 20 psi and going down to nothing, it should have open at 20.3 and held close at 14.5 psi, it did pop at 26 psi like it should. so figure I would order a cap and put the car back together and on the ground. went to start the car and it turned over couple times (cold) like normal and heard it just start to fire and loud BAM it stopped. i thought oh crap, I removed the intake filter system and was going to bar the engine over just to check, nope it is not going to let me bar the engine over in normal rotation, so I rotated the engine in reverse and it was ok, so back in normal rotation and come to a stop at the same place. Wow... maybe this week I will remove the spark plugs and rotate to see if nothing comes out of each cyl., and then go from there. i am thinking a good chance I am going to be dropping the engine out..... anybody else got some guesses. oh well. and she was running so sweet.

Do some more diagnosis before you talk about an engine drop -a major undertaking. So the engine is locked in one direction but not the opposite direction ? Are the cylinders full of coolant ?= Intermix ? Trying to compress coolant would account for the "Bam" - Unstoppable vs.un-compressible . What is the weakest link? Rod bolt?

i do not see you getting out of this cheap unless a freak accident like a coolant leak from a hose etc some how got into the intake then a cylinder. pull the plugs and go from there...........

No, the engine won't be dropped till full diagnostics are done, I've held a ASE master tech cert. and also A&P for last 35 years. since it held coolant system press. no problem for .5 hr. is the part that is confuzzling me and has me thinking mechanical. did a small head gasket leak just let go? but it held press. maybe IMS shaft or chain just happen let go. no intermix.

Was the serpentine belt off when you turned the engine? If it was not, you may want to remove it and retest. It's possible one of the pulleys/accessoroes is locked up.

I will definitely try that, I did change the belt 2 weeks ago so it has good grip.

Well, after sitting for 2 days i went and bar the engine over and had no problem barring it over thru multiple cycles, so went ahead and try to start it up, fired up no problem, let it run and started to notice a slight miss when getting warmer, hooked up Durametric Pro, had 4 F.C. one I caused with disconnected MAF sensor disconnected, and 301 and 304 for misfire, notice I was getting water vapors mostly from driver side exhaust, shut it all down after warm up and check the oil and looks like I am making oil, up pass full a half inch. going to let it sit for couple days and drop the oil after it seperate and check for coolant, also do a compression test and leak down test. maybe pressurize the system while still together and see what hole coolant can be coming out of, also drop the pan and check for coolant trail while pressurized. oh well I needed a project.

Sorry to hear that and I have to agree it doesn't sound good at all. What year is your 996?

It is a 2004 C2 with 72,000 miles. actually I am happy its not a mechanical failure like a chain or rod, hoping head gasket failure and will pull the engine and go thru it and make sure everything it within tolerances. also take of the IMS among other things. probably never give this car up investing in my toys.

or a cracked head

I thought about that also, but everything was good till I pressure tested the coolant system and then the issue came about. never overheated or use coolant before and held engine temp even on 100 degree days in summer traffic and never went above 200 with A/C on, here today just running on 50 day, temps were climbing at 2 degree's per half minute and i shut it off once it hit 209 with all accessories off.

If you haven't already, do some searches in the forum on cracked head versus head gasket failures. The results will not be encouraging, unfortunately.

I have read that numerous time about cracking heads versus HG, then again chunking could explain the making of oil also. just have to go into it.

aka Intermix