Overheating/knocking problems. 95 SE 2.3L

[NiiickMuse]

My car started overheating just this week. It happened a couple days after I got an oil change at wal mart...I noticed however that if I revd it in neutral when it was overheating the gauge would go down quite quickly. So..the next day I went to go get my girlfriend who lives about a half hour away, 1 hour round trip. Car didn't overheat once.

So, anyway...a couple days ago I was takin one of my friends home and my car started grinding and knocking when I reved it in neutral...and it was overheating like mad. Typical symptoms as I have read, no leaks at all, just overflowing through the cap, which happened the first time it overheated also. I checked my water pump and thermostat, they are both fine...I even bought new ones to put in before I looked as I was sure this was the problem. Anyway..as I was driving home it began knocking really bad and I was really afraid to keep driving it, but I was only a few minutes from home, so i drove about 20 mph the whole way home..and woke my brother up because it was so loud.

I checked my oil and it was fine...

I read about replacing the cap, and you shouldn't put it on too tight etc. Could this be the thing causing the overheating? If not I don't know what else it could be..there's no leaks at all anywhere..

Also, I can't really describe the sound the engine was making incredibly well, and I can't drive the car at all or start it until I get it back together...I was just curious if anyone had any ideas or advice at all for me..I'm thinking about getting a new car, but I'd obviously like to keep this one if at all possible as I'm getting an apartment in a week..blah blah blah.

I'll post a video of the car's engine making the noise in a few days, hopefully I'll have it together by then. Thanks for any help guys, I really appreciate it.

Car has about 127k miles on it btw...never had any problems with it until now..bought it used when it had 118k miles. It was in really good shape.

[rixGAphx]

During the first 'overheat' episode, coolant came out of the pressure cap?
How much coolant did you have to replace?

Your waterpump may have failed.
It's cam driven somehow, I'm not famliar with the 4-cyls but that's what I've read.

Personally, I'm thinking you DID (and still do) have a leak, you just haven't noticed where, yet.
I'm thinking your system was pretty low on coolant when the first episode occured, and the low level was what caused it.

The exteme knocking and poor power are symptomatic of a HIGHLY overheated cylinderhead, one that has no liquid flowing thru it to cool the metal. The metal is so hot on the insides of the combusstion chamber that the air-fuel mixture ignites as it's being compressed, even before the spark fires.

I don't know what you've taken apart so far.
But I would do a compression test to check for blown headgasket, which often results from a warped head (the warpage coming from the extreme overtemps that also caused the knocking).
A head job may also be in your future :(

And definitely pressure-test the cooling system; use some UV dye and a blacklight to determine leakage location.

Hope this helps,
-Rick

PS:
When the head overheated, it was so hot that it scorched (and destroyed) the oil that dripped off the valve train and flowed across it.
For a while there, your head was actually 'oil-cooled'.
Net result is you need another oil change, since that scorching was equivalent to several thousand miles of normal driving.

[NiiickMuse]

Yes, the first time it overheated coolant came out. I had to refill bout half of it, and it was pretty much boiling.

There is no leak at all..I checked the car everyday even prior to this for leaks..and there is still no leak anywhere.

[Matt95GT]

Sounds like the symptoms of when a Quad 4 water pump goes bad. Is the sound a whine/groan coming from lower passenger side?