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Thread: What are normal engine coolant temps? Need help with intermittent overheating

  1. #1
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    What are normal engine coolant temps? Need help with intermittent overheating

    Hey everyone, I have been chasing a cooling problem and I am looking for some help. Truck is 1993 K1500 TBI with vortec heads.

    1. What is considered the normal range for ECT?
    2. At what point would you stop the truck and wait for it to cool down?
    3. Could this be caused by me having the heater core hoses hooked up backwards? (I don't know for sure if they are - I just know that I guessed at what was correct when I put everything back together so I have a 50/50 shot that it is correct).


    Any input/advice is appreciated.

    AC

    Some background.
    1. Cooling setup is stock (fans, radiator, etc.)
    2. New water pump
    3. Not running AC (broken)
    4. Thermostat is stock (190 or 195, can't remember but I do know I bought an OEM rated stat)
    5. I live in Atlanta, Ga. (it is hot here).
    6. Sometimes the truck will run in stop-and-go traffic and never crack over 210.
    7. Sometimes the truck will creep into the 220's but eventually it will cool back down into the 205-210 range. This usually happens in stop and go traffic. It is worse in the afternoons when it is hottest outside but still happens some mornings when it is cool (hot and cool are relative here and ranges from 70-90 degrees).
    8. Coolant overflow tank never seems to change level or even come into play.
    9. No steam/boiling/etc is seen or heard.
    10. No coolant smells.
    11. Coolant level in the radiator tank remains consistent (I check it some mornings when everything is cold)
    12. Engine was refilled with fresh 50/50 after the rebuild was finished in May.
    13. When I first started driving and tuning the truck it would slowly build heat until it could no longer cool (greater than 230). I would have to turn it off and wait for it to cool.
    14. I have since learned that the stock TBI timing tables are nowhere near advanced enough for the vortec heads.
    15. Changing the main timing table TREMENDOUSLY helped the drive-ability and mostly helped the overheating problem.
    16. Still, the ECT will randomly creep up. For example today the ECT hit 227 on the way home in stop-and-go. This was after about 35 minutes of stop-and-go
    17. The truck runs "rougher" when it is over 210. Not sure if this is fuel or timing related.

  2. #2
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    Did you do the following or at least drill some holes in the thermostat? 1995 and earlier blocks have the thermostat bypass passage from the block directly to the water pump. Important: If you use this manifold on a 1996 and later Vortec engine (which doesn't have the bypass in the block), you must run a coolant bypass line from the manifold to the 5/8" hose nipple on the passenger's side of the water pump. Route from 3/8NPT tapped hole in front of the manifold."

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    Hey Stokes. Not sure if this applies to my situation. My block is a 1993. I do have vortec heads but I don't think that matters.

    My understanding is that the coolant bypass is done through the heater core. I could be mistaken though.

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    If you have a tbi block for sure then you should be good. I know my 93 k1500 has a rebuilt and just happens to have a vortec block with flat tappet cam. I would def put some holes in the thermostat though. I have read posts after posts stating that this has solved many problems with coolant issues.

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    Sounds easy enough. I'll make it happen. Any recommendation on hole size or number of holes?

    Also, you know anything about the heater core hookup? I'm worried mine might be connected backwards.

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    I have read that 2-3 5mm holes work, but I would def research a bit before so. Theres tons of info on it. I am not sure on the heater core, but in the morning I can take a look at my truck and see. Can post some pics if needed. Ive attached a file of Fast's go to timing table for vortec heads that should get you going in the right direction. Probably just minor tweaks from there
    Attached Files Attached Files

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    Sweet. I'll take a look. Thanks for this.

    So, what temp range do you consider normal? When do you start to get nervous?

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    My truck never gets over 190 with my thermostat. I would think anything over 220-230. What temp stat are you using?

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    From GM performance parts:
    Any small block engine, regardless of year, that uses Vortec heads, will require an external coolant bypass line from the intake manifold to the 5/8" hose nipple on the water pump (passenger’s side). Suggested routing is from the 3/8 NPSF boss on intake manifold to the water pump.

    What intake are you using? It sounds like your gonna need the bypass hose. Read through the beginning of this post. Lots of info

    https://ck5.com/forums/threads/vorte...i-need.298868/
    Last edited by Stokes1114; 06-16-2017 at 09:15 PM.

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    Getting late but excited about digging into the cooling issues and the timing tables tomorrow. I did open the zip file right quick and noticed a few things. Oh yea, I am running 16168625 and $E6.

    As far as screenshots in the jpeg file - what program is this?

    What is the equivalent table name for the PE/COT spark advance correction and is the equivalence ratio going to be something I have in my tune/BIN (this doesn't look familiar at all)?

    Same question for PE EQ ratio - I know I have PE but this table and the EQ ratio are not something in my BIN as best as I can tell.

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    Quote Originally Posted by Stokes1114 View Post
    My truck never gets over 190 with my thermostat. I would think anything over 220-230. What temp stat are you using?
    The stat is whatever is stock. I can't remember but either 190 or 195.

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    Quote Originally Posted by Stokes1114 View Post
    I have read that 2-3 5mm holes work, but I would def research a bit before so. Theres tons of info on it. I am not sure on the heater core, but in the morning I can take a look at my truck and see. Can post some pics if needed. Ive attached a file of Fast's go to timing table for vortec heads that should get you going in the right direction. Probably just minor tweaks from there
    WIN_20170617_09_11_05_Pro.jpgWIN_20170617_09_11_17_Pro.jpg

    Some photos of how my heater core is connected. (Please don't judge the lack of wring harness loom - this truck needed a lot of love and is work in progress). The hose closest to the drivers side (on right in photo) is connected to the intake manifold. The hose on the passenger side (left in photo) is connected to the radiator just below the rad cap.
    Attached Images Attached Images

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    2 XDL Logs and adx attached. Many strange things going on. Overall I think the tune is a bit on the rich side but I am okay with that for now. Any and all feedback welcome.

    1) I am logging knock counts continuously but there is no knock retard. I donít hear anything. Could be I donít know what knock sounds like.
    2) Engine seems to be heat soaked after driving for more than ~35 minutes. Once it gets heat soaked it never passes 230 but also never drops below 215.
    3) Every now and then the computer blips.
    4) Block learn cells jumping

    1) Logging knock counts continuously but no knock retard: I have seen this in other posts but no resolution was given. I get knock counts continuously showing up on the dashboards and in the logs but I never see any knock retard. Log 18 shows counts continuously at 268 and log 18-1 shows the counts continuously at 156. I donít hear anything. Could be I donít know what knock sounds like.

    2) Overheating stuff: I drilled 3 holes at 3/16" diameter in my t-stat this morning. I don't have a bypass plug on my water pump (or I could not see it f I do). Anyways drilling holes seemed like the easiest route. Note that it is a 195 stat in the truck. Test drove the truck this afternoon at the hottest part of the day. Took a lot longer to reach operating temp (maybe 10 mins?) so I know the holes had an impact. I still ended up getting to 225 before my drive was over. It seems like after 35-40 minutes of driving the engine is heat soaked and cooling canít keep up. Laptop battery died so unfortunately this heat soak is not reflected in the logs.

    3) Computer blips: If you export the 18-1.xdl log and look at rows 30, 31, and 2134, 2135 you will see lots of odd stuff. Kind of like the computer blipped. These rows stand out because that are different than all other rows before and after them. Is this common? The following things really jumped out at me:
    See rows 30, 31, 2134, 2135. You will immediately notice they are very strange.
    Column BS - CPI/PFI Single Fire Flag set to yes (all other rows set to no and this is a scalar right? How can this change?)
    Column BO - fuel pump relay failure
    Column DF - High Knock Activity Flag set to yes
    Column GG - Spark Advance reads 451.8
    I have seen these ďblipsĒ in pretty much all of my log files since day one. Usually only one or two rows at a time. I just figured this was normal but not it occurs that I should ask the group.

    4) Block learn cells jumping and causing some driveability issues: Does anyone have a recommendation for the BLM boundaries (Loc 0x48DD and 0x48E0 in $E6 mask) for MAP and RPM for a vortec headed TBI? I think my block learn cell is fluctuating around a low load sweet spot for my truck. It seems to jump between cell 5 and 6 around 1400 RPM. Check out 8:29 to 8:45 in log 18 as an example.
    Attached Files Attached Files

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    Quote Originally Posted by Stokes1114 View Post
    From GM performance parts:
    Any small block engine, regardless of year, that uses Vortec heads, will require an external coolant bypass line from the intake manifold to the 5/8" hose nipple on the water pump (passenger’s side). Suggested routing is from the 3/8 NPSF boss on intake manifold to the water pump.

    What intake are you using? It sounds like your gonna need the bypass hose. Read through the beginning of this post. Lots of info

    https://ck5.com/forums/threads/vorte...i-need.298868/
    I am running the GMPP TBI to Vortec intake. Expensive but I needed EGR to pass emissions (glad that's over). After reading through some other posts and various other internet sources I decided to try the holes in the thermostat. It seemed simple enough and besides, I don't think my pump has the external provision for the bypass. I remember buying a new pump for a 1993 truck during the rebuild (looks like I should have bought a 1996-1998 pump).

    Stokes, if you don't mind checking the orientation of your heater core hoses I sure would appreciate it.

  15. #15
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    There is some good info here on the Vortec coolant bypass
    http://www.gearhead-efi.com/Fuel-Inj...Manifold/page2

    I run a 94 water pump because the factory coolant bypass passage now works with the hole I drilled in the Vortec head.
    Last edited by Kitch; 06-17-2017 at 03:13 PM.

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