Overheated & Ruined My Engine?

My thermostat went bad and I drove the 2001 Suburban 1500 4WD until it
boiled, choked and stopped. It started again, but now the ride is
rough. Compression tests done..."in normal range", mechanic's say
"nothing wrong". Yes there is, it is like riding on a gravel road.
Possibly scalded a piston? Don't trust rebuilds, trying to find new
engine. Any suggestions before I spend $5500 on a new GM engine?

has the thermostat been changed, and if so, does the engine run at the
proper temps?
if it does, is it smoking, and if so what color?
is it keeping the proper amount of coolant, or is it leaking, or
dissapearing?
if cooling system is fine, tune it up.

187 wrote:
> has the thermostat been changed, and if so, does the engine run at the
> proper temps?
> if it does, is it smoking, and if so what color?
> is it keeping the proper amount of coolant, or is it leaking, or
> dissapearing?
> if cooling system is fine, tune it up.

Thermostat been changed, engine runs at proper temps. No smoking.
Keeping coolant, compression test "within normal limits. Plugs were
changed at my request. Car still "shudders". Very slight, but there.
Also, has reduced engine power.

Three questions off the top of my head:

What does an engine-vacuum gauge tell you while the problem is
occurring?

Was the compression test held for a time on each cylinder to watch for
bleed-down, and if so, what does *that* reading look like on each one?

Those two are looking for something mechanically damaged, like a
marginal gasket or a warped head. But as long as you're underhood: is
On-Board Diagnostics II showing any trouble codes? (As if you'd
cooked a sensor somewhere? )

Free bonus question, assuming this is port fuel injected: are the
injectors all happy?

Also: any exhaust gases in the coolant? any coolant in the oil?

Now for the good news: from the symptoms you described, and most
importantly the things others mentioned that you considered and
cleared, I am not really guessing that you ruined the engine; we're
probably looking for more subtle things. Close escape!

--Joe

im not sure on that engine if it has coil packs, or a distributor, but if
it has coil packs, check the cam and crank sensors, if it has a
distributor, check it, and your timing.
also make sure your firing order is correct, and that you don't have any
vaccum leaks.
matt

Hope you changed the oil after it got so hot!!!

Dumass wrote:
> My thermostat went bad and I drove the 2001 Suburban 1500 4WD until it
> boiled, choked and stopped. It started again, but now the ride is
> rough. Compression tests done..."in normal range", mechanic's say
> "nothing wrong". Yes there is, it is like riding on a gravel road.
> Possibly scalded a piston? Don't trust rebuilds, trying to find new
> engine. Any suggestions before I spend $5500 on a new GM engine?