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rough idle after overheating
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furthur67
New User
Jun 2, 2008, 3:54 PM
Post #1 of 6
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rough idle after overheating
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'91 Ford Mustang 2.3L 150,000 miles
The car overheated, the water didn't seem to be flowing and was backing out of the overflow, etc., so I checked the thermostat. It came out in 2 pieces, without the copper actuator (which I never found). I replaced the thermostat with a new one and it overheated again. I checked the new thermostat by boiling it in water and it didn't open. I bought a 2nd new thermostat and checked in boiling water and it opened (I also checked the 1st new one again at the same time and it still did not open). I ran the car with no thermostat for 45 min. and it didn't overheat, but idles very rough. We took it for a test drive, it drives well at higher speeds but still idles very rough. Could this be a sign of damage from overheating (valves, lifters, etc.) or could some fuel sensor been affected making it run rich?
Thanks
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jun 3, 2008, 2:47 PM
Post #2 of 6
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Re: rough idle after overheating
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arggh! Would be nice to get the missing peice out. How big does it look in new one compared to what's missing in the original?
If overheated enough and sometimes things happen anyway it could have hurt the head gasket, head or unknown at this time. Missing part in engine isn't helping with diagnosing this
T
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furthur67
New User
Jun 3, 2008, 3:43 PM
Post #3 of 6
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Re: rough idle after overheating
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The piece is 1/2" dia. x 1" long, same as old one presumably. It's possible that I dropped it and it landed on a pulley or something and it fell off while driving. That's my hope anyway! It seems more unlikely that it fell in, being that water flows toward the radiator, although I still have some worries about it.
What would some symptoms of head or head gasket damage be? The oil looks good.
Thanks for the reply.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jun 4, 2008, 2:19 AM
Post #4 of 6
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Re: rough idle after overheating
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Notes and guesses on this: It overheated to begin with and that's a problem in any car. Chicken and Egg scene now as what caused it first and what is the problem now??
Ok: The first thermostat probably did fail if it physically broke there's no telling now what its problem was or that the car overheated so bad it started to ruin things - head gasket is a weak area and is strongly in the possible section now with what I see here.
1. Overheated and now still does and now has rough idle. Will run cool with no thermostat and not with now know good replacement with parts from original possibly still in engine. Note: Flow probably isn't enough to push metal parts along wherever those parts went.
Note again: Thermostat out means water pump can pump coolant directly out of end of engine to radiator and return cooled liquid back quickly which doesn't allow for the mixing of all the coolant in far reaches of the engine so it could be overheating where the sensor isn't sensing - that also causes metal parts to expand unevenly and can ruin a head gasket! Arggh - Word of the day here....
2. You found a new thermostat that wouldn't open in boiling water - wow! Not common but happens....
**** What I think is happening now is that the head gasket is allowing air (combustion gasses) into the cooling system which makes is a bubbly mess which really can't cool well but when unobstructed gets enough flow to at least fool the system as with no thermostat in it. Any time engine is hot or pressures up from bubbles - either from actually boiling or added gasses it will blow out to recovery tank and even over that to ground.
3. Now it doesn't idle well which suggests that a cylinder (hmmm - perhaps the one with a possible compression loss thru head gasket to cooling system??) Head gasket seal oil, air, compression coolant ---- everything from each other and can fail in any direction IE water in oil, oil in water or leak outside engine and more fun.
{{Ever go to a block party and someone "blows a gasket" and you never know just what their behavior will be?}}
Ok: I'd pressure test the cooling system and watch out as it might fill a cylinder with coolant and lock if you try to start it. Take plugs out and check for evidence of whatever and crank with them out if wet with anything and move on to a compression test.
If the radiator isn't in good shape that could have been the problem to begin with - check that out and flush the system. Fan must work properly too and could have been the problem.
Test out to verify as a head gasket job is enough aggrevation to avoid doing if not needed. If found to be a fault now send out the head to machine shop to "shave and inspect it"
The missing parts don't make this much fun and there's no telling if they will continue to haunt it or could be harmlessly in some place that you may not find - that's a thorn in the diag that may never be pinned down.
My guess on that is they will be ok if not found - guess only.
Diagnos a lot for this. It's a 91 Escort and if you aren't up for this job yourself this could be huge bucks for a car that old,
T
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furthur67
New User
Jun 4, 2008, 4:27 AM
Post #5 of 6
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Re: rough idle after overheating
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Wow, it will take me a while to parse through this reply... I'll have to wait until I get home from work. I was worried about the head gasket because it doesn't seem to have proper compression to me, but I know very little.
The radiator was leaking a couple of months ago and stop leak took care of that. Does the stop leak ever cause a problem with an old radiator?
Thanks for the in depth opinion, it is very much appreciated!
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jun 4, 2008, 4:56 AM
Post #6 of 6
(16095 views)
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Re: rough idle after overheating
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Smile - I'm well known for being so "verbos" !!
Stop leak: It can work but will aggrevate the heat transfer ability of the system at large and be the cause of inadequate cooling - hence overheat which then causes the hair loss of more problems. Old doesn't equal bad for a radiator, its condition just needs to be checked out and the leak should be fixed or the radiator replaced if bad enough, won't flush out, or corroded. If it works at all that isn't the issue at hand right now but on the list ever growing. Head gasket could change, lower compression on one or more cylinders.......
T
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