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  • Hot but not overheating...yet.

    With warm weather finally here I noticed my engine is running hotter than usual. Not overheating but it's clear the cooling system is having issues keeping up. Driving on the highways is fine but as soon as I enter stop/go traffic the temp climbs up to 220F. The fan kicks in but it struggles to bring the temp down even when it's only 75F ambient. This doesn't bode well with the summer weather coming soon. The upper radiator hose does get hot and no part of the radiator I can reach seems to be colder than the rest save for the very bottom.

    While driving around with scannerpro I see that the max spark advance in the histograms are a little scary. It's as high as 39* in the 2000 RPM, 40&50 kpa cells. The minimum advance in the same cells were 26-28*. This seems like a lot to me although I'm not seeing any more than 1 knock counts per driving cycle and I don't feel/hear the engine pinging or detonating. The BLM's on 'most recent samples' are a little low with most at less than 120. Yet at WOT where the BLM's are at 128, the engine runs stupid rich at 10.5:1-11:1.

    The engine is pretty much as it came from the factory with 130,000 miles. While it feels on the tired side it doesn't burn oil or coolant although there is some external coolant seepage along the lim gasket. Coolant system still pressurizes. Compression is between 170-180 psi. The low BLM's with the over-rich WOT I think is just from still running the original timing chain. I haven't seen listed symptoms for TC stretch that include overheating though.

    Recent maintenance: Coolant flush in feb. at a dealership. No air coming through bleeder. Knock sensor is new. Injectors are clean and fuel pressure is good. Hosed outside of rad to clear any dirt. Straightend any bent rad/condenser fins I could find. Entire ignition system is less than a year old. Switched from the LC-1 wideband back to a narrowband. Waterpump ~1 year old.

    Any ideas on what else I can look into? I'm also tempted to drain the radiator to see if there's any sludge or sediment that comes out but I can't figure out how to open the drain valve.
    1995 Grand Am SE

  • #2
    Couple of things. One, 220 ain't hot no more. Many many GM's do not turn on fans till 226 or so if you are not using the A/C and the fans are waiting on temp. Second, at full throttle loads, the block learn will blip to 128 as she goes into open loop for acceleration enrichment mode, and being between 10 and 12 to 1 is no crime for heavily weighted gas pedal

    If you ain't rock and roll, you must be driving a Honda

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    • #3
      The radiator fan should still be able to cool the engine to the fan turn-off point and cycle between on/off as needed. What I'm saying is that mine is only capable of doing this on a cool day. It was 95F yesterday and when the fan kicked in it was struggling to keep the engine temp from getting higher.
      1995 Grand Am SE

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      • #4
        The radiator probably has obstructed tubes. Either that or the t-stat is not fully opening.

        If you ain't rock and roll, you must be driving a Honda

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        • #5
          Drained the coolant to swap the thermostat and it came out a brown-ish green. No sediments or oil that I can see. Potential headgasket seepage or just rust in the block? I'll use new coolant either way.
          1995 Grand Am SE

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          • #6
            Either the fresh coolant and/or the new thermostat seems to have improved things. The old fluid seriously looked like someone dumped some iced-tea in it. Maybe the mech who did the flush added a stop-leak additive and forgot to mention it. I'll give the system a proper hose-out when I change out the lim gasket for a 2nd time.
            1995 Grand Am SE

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            • #7
              On an older vehicle, it's not uncommon for the radiator fins to become plugged over time with bugs, dirt, grass, etc. And it happens so gradually that it can be hard to know when/if this becomes a problem. I see it all the time with heavy trucks, and dealt with it in my own '94 Corsica last summer.

              The thing wasn't overheating bad, but if I parked somewhere on a hot day and sat for a while at idle- the temp would climb and the fans would never cycle off. Long story short, I removed the radiator and could see that a lot of crud had built up on the OUTSIDE. I cleaned it thoroughly with the shop's steam cleaner and also cleaned out the a/c condenser fins. Put it back together, and the thing cools great. The gauge never goes much past the thermostat opening point even on hot days.

              One other cooling system problem that I've had with this same car involved internal sludge. I imagine you know about Dexcool's amazing ability to turn into mud if conditions deteriorate. About ten years ago- back when I first met my wife (and the '94 Corsica was HER car), the old Corsica had a nasty habit of overheating. It did ok most of the time around town and even on the highway- but if you started up a hill for any length of time (we were in Colorado), the temp would start climbing. I noticed that the coolant tank had lots of a nasty mud-like substance in it (this car did not originally come with Dexcool, but somebody had swapped it into the car). Long story, but I ended up pulling the radiator and took it to a radiator shop. He took a tank off, and it was thoroughly sludged. He cleaned out the radiator and rodded out the tubes. Put it back together, and it cooled great... well until last summer when the external fins plugged.

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              • #8
                Thankfully my car is pre-dex-cool and the previous owner didn't use it. I'm kind of kicking myself for not taking the extra two steps to yank my rad out to give it a thorough cleaning when I had the system drained. There was a collection of dead bugs between the condensor and transmission cooler. Stupid carcasses fell in-between at the top and got stuck. Adding spacers at the bottom of the cooler should prevent it.
                1995 Grand Am SE

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                • #9
                  This isn't a widely accepted procedure, but here's how I've dealt with that problem with my '94 Corsica and the wife's '01 Lumina. With both cars, after I cleaned out the radiator and condenser, I sealed gap around the perimeter between the radiator and a/c condenser with foam. I cut strips of closed-cell foam and glued them in place where it was convenient- and used spray-foam where necessary. The idea is that any air that goes through the radiator HAS to go through the condenser first. I mainly did this to improve the air conditioning by increasing airflow across the condenser (air can't be sucked in around- has to go through).

                  I got the idea from the John Deere tractors that I used to work on- they pack the area around their radiators with closed-cell foam to direct airflow and control where dirt builds up.

                  Anyhow, keeping bugs out is a secondary benefit. I covered the condenser with fiberglass window screen, which catches pretty much all the bugs and assorted crap. Rather than jamming in between the fins and getting sucked in further, they tend to stick to the screen- then dry up and fall off. Both vehicles went 9+ years before I needed to clean out the radiator/condenser fins... so I expect that with this setup, I shouldn't have to clean them out again for the rest of the vehicle's life.

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                  • #10
                    ^^ now there's an idea.... i just went through the pain of doing it on the MC...the bottom row of the condensor's fins were trashed...
                    1995 Monte Carlo LS 3100, 4T60E...for now, future plans include driving it until the wheels fall off!
                    Latest nAst1 files here!
                    Need a wiring diagram for any GM car or truck from 82-06(and 07-08 cars)? PM me!

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                    • #11
                      I like the screen idea as long as it's still getting enough air flow. It's amazing the difference between an open window with a screen, and one without. Being assigned to Ladder Trucks for the first 16 yrs of my fire career made me a ventilation expert and when using positive pressure to ventilate a structure you learn really fast how much normal everyday screens restrict the air flow. The only thing worse are those little freaking vents they put in glass block windows, lol.

                      Axe
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