View Full Version : 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.
What is considered the normal range for ECT?
At what point would you stop the truck and wait for it to cool down?
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.
Cooling setup is stock (fans, radiator, etc.)
New water pump
Not running AC (broken)
Thermostat is stock (190 or 195, can't remember but I do know I bought an OEM rated stat)
I live in Atlanta, Ga. (it is hot here).
Sometimes the truck will run in stop-and-go traffic and never crack over 210.
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).
Coolant overflow tank never seems to change level or even come into play.
No steam/boiling/etc is seen or heard.
No coolant smells.
Coolant level in the radiator tank remains consistent (I check it some mornings when everything is cold)
Engine was refilled with fresh 50/50 after the rebuild was finished in May.
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.
I have since learned that the stock TBI timing tables are nowhere near advanced enough for the vortec heads.
Changing the main timing table TREMENDOUSLY helped the drive-ability and mostly helped the overheating problem.
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
The truck runs "rougher" when it is over 210. Not sure if this is fuel or timing related.
Stokes1114
06-17-2017, 06:20 AM
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."
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.
Stokes1114
06-17-2017, 06:38 AM
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.
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.
Stokes1114
06-17-2017, 06:50 AM
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
Sweet. I'll take a look. Thanks for this.
So, what temp range do you consider normal? When do you start to get nervous?
Stokes1114
06-17-2017, 07:02 AM
My truck never gets over 190 with my thermostat. I would think anything over 220-230. What temp stat are you using?
Stokes1114
06-17-2017, 07:12 AM
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/vortec-head-swap-what-do-i-need.298868/
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.
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.
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
1191111912
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.
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 don’t hear anything. Could be I don’t 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 don’t hear anything. Could be I don’t 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 can’t 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 “blips” 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.
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/vortec-head-swap-what-do-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.
Kitch
06-18-2017, 01:10 AM
There is some good info here on the Vortec coolant bypass
http://www.gearhead-efi.com/Fuel-Injection/showthread.php?2542-WTB-GMPP-TBI-Vortec-Intake-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.
There is some good info here on the Vortec coolant bypass
http://www.gearhead-efi.com/Fuel-Injection/showthread.php?2542-WTB-GMPP-TBI-Vortec-Intake-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.
Dude! What a great thread. Thanks for this!!
Stokes1114
06-18-2017, 01:40 AM
Just have a sec to reply, I looked at your pic and your heater core setup is identical to mine. From the back of intake it goes to the core then from core to the radiator, just below the cap. Ill have more time in a bit so Ill be back with some more info for you.
Kitch
06-18-2017, 02:21 AM
Maybe you could look at temporarily bypassing your heater core so the return goes straight back to your radiator and see if that makes any difference?
Good idea. I think I'll pull the tstat also. Get back to basics. Prove that radiator and pump work.
Fast355
06-18-2017, 06:17 AM
My 350 Vortec in my 1997 Express van ran hot until I put a 454 radiator, a HD fan clutch and a diesel mechanical fan on it. Hotest I have seen it run is 203°F and that was towing a big trailer and coming to a dead stop in rushour traffic with the A/C blasting.
My 350 Vortec in my 1997 Express van ran hot until I put a 454 radiator, a HD fan clutch and a diesel mechanical fan on it. Hotest I have seen it run is 203°F and that was towing a big trailer and coming to a dead stop in rushour traffic with the A/C blasting. I hope I don't have to go this far. Any chance the 454 rad is a bolt for my 93?
Was hoping someone could help with the other stuff too. I am really confused on the constant spark knock counts and no spark retard. Also the random blips in my log and lastly the block learn cells. Much obliged to anyone who can offer some assistance.
jim_in_dorris
06-18-2017, 05:57 PM
The spark knock count is cumulative, if it isn't continually incrementing, you are fine.
The spark knock count is cumulative, if it isn't continually incrementing, you are fine.
Thanks Jim. Good to know. Is it normal to have a few knock counts at startup?
steveo
06-18-2017, 07:33 PM
Was hoping someone could help with the other stuff too. I am really confused on the constant spark knock counts and no spark retard. Also the random blips in my log and lastly the block learn cells. Much obliged to anyone who can offer some assistance.
the knock senor is a microphone
the knock sensor is connected to a circuit that converts analog acoustic waveforms to "knock events" if they are a certain pitch and amplitude that the filter thinks might be knock
the ecm recieves these events. it then computes knock retard from those events based on your calibration. you have some software control of this behavior, including attack and decay.
the knock count itself is just a total of knock events, like an odometer, and is only for datalogging, the ecm doesnt use it for anything (just like you dont look at your odometer to see how fast you're going)
a knock count may cause zero retard if your tune doesnt allow kr in that condition, for example if your max timing retard vs rpm is zero, or your min coolant temp for kr isnt reached yet.
also other things may cause knock retard depending on your ecm's program
the knock senor is a microphone
the knock sensor is connected to a circuit that converts analog acoustic waveforms to "knock events" if they are a certain pitch and amplitude that the filter thinks might be knock
the ecm recieves these events. it then computes knock retard from those events based on your calibration. you have some software control of this behavior, including attack and decay.
the knock count itself is just a total of knock events, like an odometer, and is only for datalogging, the ecm doesnt use it for anything (just like you dont look at your odometer to see how fast you're going)
a knock count may cause zero retard if your tune doesnt allow kr in that condition, for example if your max timing retard vs rpm is zero, or your min coolant temp for kr isnt reached yet.
also other things may cause knock retard depending on your ecm's program
This is much clearer now. I understand microphones, frequency/pitch and amplitude a lot better than EFI so I get this.
My tune started with a read of the stock BIN so the knock retard settings should be whatever GM put in there. I haven't changed them. It seems that I am getting a few knock counts at startup but none while driving so I'll stop worrying about the knock.
On to the block learn cells. Is there a recommended setup here or do most people leave this set the way GM has it?
steveo
06-19-2017, 06:48 AM
knock counts on startup are 100% normal.
you want decent blm coverage. in a 3x3 grid you want low/medium/high load and low/medium/high rpm. you dont need coverage where power enrichment takes over. this can change as your engine build produces different ranges of map and rpm. the idea is you don't want high load corrupting low load memory, etc.
Fast355
06-19-2017, 08:21 AM
I would consider finding a GMT400 Tahoe or Suburban and getting the larger radiator mounting brackets and fan shroud before trying to fit the 454 radiator. Perhaps even grabbing the radiator. You would be surprised how many newer radiators and other parts are in junked vehicles. Those vehicles have a 34" wide radiator with a double wide core. I went to the 454 radiator in my Express because it already had the biggest small block radiator offered for that application in it. Those SUVs also had a larger plastic fan with about 11 blades on it.
is the water pump the same as before you made head changes? some pumps are made to pump in reverse. could be the radiator starting to clog to. fan clutch weak fan shrould not fitting .
Updating thread in case someone else has a similar problem and finds themselves here.
After drilling 3 holes of 3/16" diameter into my tstat my overheating problems have disappeared. Note that it now takes at least 10 minutes for the truck to get to operating temperatures and this may be problematic in the winter. Also I will be adding an aftermarket water temp gauge because the gauge on the dash has proven itself to be unreliable.
My setup is a 1993 TBI block with vortec heads, General Motors Performance Parts (GMPP) TBI to vortec intake, TBI water pump (without a bypass connection), and 195 degree stat.
Analysis: I was not getting bypass flow around the thermostat to prevent localized hotspots. Adding the 3 holes in my tstat allows for enough coolant to always flow from radiator, through the water pump, through block, through heads, out of the intake manifold, through the holes into the tstat, and back into the radiator.
As to why the holes in the tstat were needed....... I can tell you it worked and it got rid of my overheating problems. Overall I think it was a combination of many factors including my timing tables being waaaaay off from what is needed for a vortec head on a TBI setup. Here is what I have gathered as to why this worked. The TBI trucks have continuous bypass flow (with the idea being the closed thermostat is what is bypassed) that is internal to the pump, block, and heads. So with the thermostat closed the flow path would be from rad, through a dedicated passage in the water pump, through dedicated passages in the block, through dedicated passages in the heads, out of the heads into the "common" coolant passages in the intake manifold, out of the manifold and through heater core, and finally back into radiator (this back into the radiator part here is where flow returns "after" the closed thermostat thus bypassing the closed thermostat). From what I can tell the TBI trucks do not have a heater control valve so with the stock heads there is always flow bypassing around the closed thermostat through the heater core. It does not seem to matter what way the heater core is connected but if your heater core was clogged you may see overheating problems. My trouble arose when I added the vortec heads - these heads block the passage of coolant from the block to the manifold. Apparently the vortec can be drilled out to allow for it but if you are reading this it is probably too late for you. Your best (easiest) bet is to drill holes in your stat. I may add the newer (1996 and later) water pump with the bypass connection at a later time but for right now I am going to stick with my current setup.
I will try to remember to come back and update this thread with how annoying the long warmup times are when the weather turns cold.
Hope this helps someone else out there one day. Thanks,
AC
More updates:
1) What is considered the normal range for ECT? No consensus. Probably 190-205 depending on your thermostat rating.
2) At what point would you stop the truck and wait for it to cool down? No consensus. I have set my personal number at 229 or greater - as long as there was no audible boiling or overflow. If there was boiling or overflow I would immediately stop the truck.
3) Could this be caused by me having the heater core hoses hooked up backwards? No. It does not matter how the heater core is connected on a 1993 TBI truck. There is not a heater control valve and there is no flow restriction in the heater core. My particular problem was that vortec heads were blocking internal coolant passages that allowed for coolant to bypass around the thermostat. The small amount of bypass flow is needed to prevent local hot spots in the cylinder heads.
Even more updates:
1) Logging knock counts continuously but no knock retard: I was not logging knock counts continuously. The knock counter is cumulative - like your odometer. Jim and steveo explained this well (see above)
3) Computer blips: No answer yet.
4) Block learn cells jumping and causing some drive-ability issues: This can be tuned out. Once I resolve this issue for my setup I will come back and post it here.
Thanks,
AC
lionelhutz
06-23-2017, 07:53 AM
People call it a bypass but it's not a bypass for the thermostat to let coolant flow past the thermostat into the radiator. It is a path that allows coolant to circulate in the block and heads with the thermostat closed.
In a typical installation the heater hoses are connected to the intake beside the thermostat and to the port on the side of the water pump. This allows coolant to circulate in the block just fine with the thermostat closed. The water path is from the pump into the block, up into the heads, forward into the front intake coolant crossover, out to the heater core and then back into the pump.
I don't know the heater configuration on your application though. Is it one hose to the intake and the other hose to the radiator? That configuration should still cause flow in this path - pump to block to heads to intake to heater to radiator to pump.
In both cases, the heater hose is likely connected to the passenger side of the intake but this just means the coolant flows from the drivers head to the hose passing by the thermostat so it detects the coolant temperature.
If the heater is configured so the hoses go to the water pump port and the radiator then that would not allow coolant to circulate in the block. I can't see the heater working very well either though since it would be using coolant from the radiator and not right from the engine.
Your description of the internal block passageway is wrong. The coolant flows down from the head into the block and then into the pump, not the other way around. When the pump pushes the coolant into the block then heads and finally up to the intake, the passage lets some of that coolant flow back to the pump.
In your particular engine you might have been getting a little air at the thermostat when cold so it wasn't detecting the hot coolant as quickly when the engine was started.
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