91 Legacy, overheated, now runs bad

[Dude]

hi,
i have a 91 legacy and last week the upper radiator hose ruptured. i
didnt notice right away so it overheated. i changed the hose, topped
off the radiator (after it cooled), then it started to backfire and run
really rough the next time i drove it. when i'm up to about 35 mph it
smooths out some but still backfires. no white smoke from exhaust.. no
oil in cooland nor coolant in oil from my observation. any ideas?
thank you in advance
Dude

 

[Carl 1 Lucky Texan]

hi,
i have a 91 legacy and last week the upper radiator hose ruptured. i
didnt notice right away so it overheated. i changed the hose, topped
off the radiator (after it cooled), then it started to backfire and run
really rough the next time i drove it. when i'm up to about 35 mph it
smooths out some but still backfires. no white smoke from exhaust.. no
oil in cooland nor coolant in oil from my observation. any ideas?
thank you in advance
Dude

CEL light on? Temp. gauge normal? Had a mech. examine it? Mileage? Time
since last service? How hot did it get before the engine was shut off?

Carl

 

[Dude]

i'm not sure what the CEL light is but the vehicle has 176k miles. it
was serviced about 8 months ago. the temp gague didnt reach the red
mark but it did get pretty high. it never shut off.. it just backfires
and runs rough.
thanks for your reply

 

[Phil Marshall]

i'm not sure what the CEL light is

Check engine light

 

[Ralph E Lindberg]

hi,
i have a 91 legacy and last week the upper radiator hose ruptured. i
didnt notice right away so it overheated. i changed the hose, topped
off the radiator (after it cooled), then it started to backfire and run
really rough the next time i drove it. when i'm up to about 35 mph it
smooths out some but still backfires. no white smoke from exhaust.. no
oil in cooland nor coolant in oil from my observation. any ideas?
thank you in advance

Warped heads come right to mind

--

 

[Michael Pardee]

i'm not sure what the CEL light is but the vehicle has 176k miles. it
was serviced about 8 months ago. the temp gague didnt reach the red
mark but it did get pretty high. it never shut off.. it just backfires
and runs rough.
thanks for your reply

I fear the heads warped - it is almost inevitable for an aluminum head on an
iron block (which nearly all engines are today) when the coolant is lost.
The temperature indication is often falsely low under those conditions
because the sensor is no longer in coolant.

A good shadetree test is to start with a cold engine - start the engine,
remove the radiator cap and pinch off the tubing to the reservoir, and place
the palm of your hand over where the cap goes. If you feel a steadily rising
pressure within a couple seconds or (worse) pulsations the head(s) has/have
to come off for repair. A shop can do a hydrocarbon test on the coolant to
confirm the results before taking the big step.

Mike