The upper hose is pretty solid during run time. I haven't really noticed how it is with the vehicle off, honestly it never crossed my mind. I'll check that in the morning.
CK5
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Engine not reaching operating temp
- Thread starter Slade001
- Start date
The upper hose is pretty solid during run time. I haven't really noticed how it is with the vehicle off, honestly it never crossed my mind. I'll check that in the morning.
I went ahead and checked the service manual, instead of guessing. I suppose it might be good for that? 
Unfortunately, it's slightly more than useless in this issue. The procedure is (on a cold engine) to use a temperature sensitive "crayon" that melts at 188*. Mark the thermostat housing with it. Remove radiator cap. Start engine and warm up at a fast idle. Watch for coolant flow prior to the mark on thermostat housing melting. If coolant flows before it opens, the thermostat is faulty.
If it's not faulty "it's something else". Ok, not a direct quote, but that is where the diagnosis ends....problem not thermostat.
Unfortunately, it's slightly more than useless in this issue. The procedure is (on a cold engine) to use a temperature sensitive "crayon" that melts at 188*. Mark the thermostat housing with it. Remove radiator cap. Start engine and warm up at a fast idle. Watch for coolant flow prior to the mark on thermostat housing melting. If coolant flows before it opens, the thermostat is faulty.
If it's not faulty "it's something else". Ok, not a direct quote, but that is where the diagnosis ends....problem not thermostat.
Where do I get a temperature sensitive "crayon"?
Welding supply places should have em. They get used when pre-heating...keep warming the part up til the crayon melts then weld. Not sure I've ever seen a 188 F temp crayon though.
Honestly, with two Delco's having been swapped on, I posted that simply to inject what GM's test procedure is for overcooling, vs. what you should really do.
I don't think it's a bad idea to test necessarily, but if a 188* crayon is hard to find, it might be a bit low on my testing priority list.
Do you have a scan/datalogging tool of any type? If the CTS is working properly (on cold engine prior to first start of day, or after sitting 8 hours or so IMO, does it read ambient air temp?), you should be able to watch the coolant temp come up, and watch for coolant for flow at the same time.
A mechanical gauge would do the same thing of course, assuming it's calibrated right, and in a spot that is pretty near the temp the thermostat sees.
I don't think it's a bad idea to test necessarily, but if a 188* crayon is hard to find, it might be a bit low on my testing priority list.
Do you have a scan/datalogging tool of any type? If the CTS is working properly (on cold engine prior to first start of day, or after sitting 8 hours or so IMO, does it read ambient air temp?), you should be able to watch the coolant temp come up, and watch for coolant for flow at the same time.
A mechanical gauge would do the same thing of course, assuming it's calibrated right, and in a spot that is pretty near the temp the thermostat sees.
Actually I JUST checked the upper hose. I let the truck idle for about 1/2 an hour while I was walking the dog and its NOT firm at all. Very little pressure collapses it. I checked the temp gauge on the dash, it read about 150-160. Ambient temp here is about 10 to 15. The cooling fan was surging. Am I correct that as a thermostatically controlled clutch, it should NOT be doing anything but free wheeling prior to "operating temp"? Maybe I DO have either a bad CTS or fan clutch. 
Any other thoughts are whole heartedly welcome.
Any other thoughts are whole heartedly welcome.
The system should be pressurized as it warms up (on mine, as soon as it starts the hoses firm up regardless of temp FWIW). That's what the radiator cap does. I can't believe a cap would cause an issue with underheating, but do you have a spare one around you can throw on just for fun? Regardless of the cap it should still get hot, but you'd expect to see it start dumping into the overflow if radiator is full and it's getting near operating temp if the cap was not sealing.
I wouldn't use the temp gauge on the dash for precision (although they normally are pretty good), but as a guide, perhaps. It should be freewheeling after a few seconds of running. But since they normally stay "locked up" when cold for a few seconds, odd operation may just be related to the cold ambient temps? You normally see a substantial amount of liquid on the hub of the clutch if it's leaking. Service Manual says if you can't turn the fan by hand with the engine off and cold, the clutch is bad.
CTS has nothing to do with the gauge, and the thermostat is the ONLY thing that controls minimum engine temp. Just for clarification, both the Delco t-stats were 195* as well, right? I know you said 195*, but you've had three, just making sure.
I wouldn't use the temp gauge on the dash for precision (although they normally are pretty good), but as a guide, perhaps. It should be freewheeling after a few seconds of running. But since they normally stay "locked up" when cold for a few seconds, odd operation may just be related to the cold ambient temps? You normally see a substantial amount of liquid on the hub of the clutch if it's leaking. Service Manual says if you can't turn the fan by hand with the engine off and cold, the clutch is bad.
CTS has nothing to do with the gauge, and the thermostat is the ONLY thing that controls minimum engine temp. Just for clarification, both the Delco t-stats were 195* as well, right? I know you said 195*, but you've had three, just making sure.
Yes, all 3 thermostats were 195º. I don't have a spare cap at the moment. I can get one in the morning and see if that makes a difference. The cap that I have on there is a "locking tab" type. It hasn't popped and there is fluid in the overflow.
I was thinking the CTS, due to the fact that the SES keeps coming on with the coolant temp code.
Thanks for all your help Dorian.
I was thinking the CTS, due to the fact that the SES keeps coming on with the coolant temp code.
Thanks for all your help Dorian.
You are getting a low coolant temp code, and your factory gauge is reflecting that the temp is low as well, so unless the CTS and temp sender both incorrectly read low for some reason (although possible, not at all likely IMO), those two reflecting low, plus your interior heat being inadequate all point to an actual low temp issue. At least IMO.
I don't suggest throwing parts at problems, especially something like a cap at an underheating motor, but it's up to you. I don't see at all how the cap should keep the temp from coming up, but the sole purpose of the cap is to keep pressure in the motor, and it's apparently not doing that.
I suppose you could remove the overflow hose from the coolant recovery tank, and plug that with a screw or something, see if it starts pressurizing the system then, although I suspect a screw won't hold anywhere near what the cooling system is capable of producing. I'd not want it pointing at me when/if it let go.
I don't suggest throwing parts at problems, especially something like a cap at an underheating motor, but it's up to you. I don't see at all how the cap should keep the temp from coming up, but the sole purpose of the cap is to keep pressure in the motor, and it's apparently not doing that.
I suppose you could remove the overflow hose from the coolant recovery tank, and plug that with a screw or something, see if it starts pressurizing the system then, although I suspect a screw won't hold anywhere near what the cooling system is capable of producing. I'd not want it pointing at me when/if it let go.
I'm at a loss as to where to go from here. I've read as many forums and articles about this problem as I could find and followed all the advice I thought feasible.
I originally changed the radiator because it seemed to be the original. It was leaking. The heater core return port had been "glued" back on by the PO.
I originally changed the CTS because I read that it being bad could account for a rough running engine and the low temp.
I agree throwing parts at the problem isn't the solution, but what's the next step?
I originally changed the radiator because it seemed to be the original. It was leaking. The heater core return port had been "glued" back on by the PO.
I originally changed the CTS because I read that it being bad could account for a rough running engine and the low temp.
I agree throwing parts at the problem isn't the solution, but what's the next step?
If it were me, I'd plug the overflow and see what happens with pressure. If it blows out the screw in short order (cap should hold whatever it says, 15/16PSI?) then the cap is bad and it won't hurt to replace it.
Another thought...what shape is the "seat" for the thermostat on the intake and thermostat housing in, and does it clamp the thermostat in pretty good? If the edges of the thermostat don't seal, then coolant is just going to bypass it.
In doing a bit of google searching, I read where someone had clamped the upper hose flat to see if restricting the flow solved the issue (as a test, not solution), and I also read that you can try to feel the upper hose for heat when the thermostat is supposed to be closed, but that sounds pretty imprecise to me. At least it's free.
With even Delco going Chinese now, its going to be harder and harder to say Delco=works correctly unfortunately.
Another thought...what shape is the "seat" for the thermostat on the intake and thermostat housing in, and does it clamp the thermostat in pretty good? If the edges of the thermostat don't seal, then coolant is just going to bypass it.
In doing a bit of google searching, I read where someone had clamped the upper hose flat to see if restricting the flow solved the issue (as a test, not solution), and I also read that you can try to feel the upper hose for heat when the thermostat is supposed to be closed, but that sounds pretty imprecise to me. At least it's free.
With even Delco going Chinese now, its going to be harder and harder to say Delco=works correctly unfortunately.
Don't know about the condition of the seat. The last 2 times that I changed the thermostat I was in such a rush to get it in and stop the coolant from running all over, I didn't have time to look.
I'll try plugging the overflow hose tomorrow when I have more time.
Thanks again for everything.
I'll try plugging the overflow hose tomorrow when I have more time.
Thanks again for everything.
Two things I's do at this point.
1. If you have an IR temp gun, the kind with a laser you can read temperatures at T stat etc...
https://www.google.com/search?q=inf...ADA&ved=0CAgQ_AUoAA&biw=1344&bih=771&dpr=1.25
2. or pull T stat and boil it and see when it opens... I use my IR heat gun for temps on this too though... can use a cooking temp gauge like one you stick in a turkey.
Have seen 195 T stats open at 180 and also seen them stick open a little bit when supposed to close... non were AC delco but there's some controversy as to the quality of AC parts now as AC was sold and... well who knows?
Do you have a cable to data log with TunerPro RT? If so what does that temp say the engine is running when warmed up? Mine with a 195 T stat runs between 195 and 200*f.
1. If you have an IR temp gun, the kind with a laser you can read temperatures at T stat etc...
https://www.google.com/search?q=inf...ADA&ved=0CAgQ_AUoAA&biw=1344&bih=771&dpr=1.25
2. or pull T stat and boil it and see when it opens... I use my IR heat gun for temps on this too though... can use a cooking temp gauge like one you stick in a turkey.
Have seen 195 T stats open at 180 and also seen them stick open a little bit when supposed to close... non were AC delco but there's some controversy as to the quality of AC parts now as AC was sold and... well who knows?
Do you have a cable to data log with TunerPro RT? If so what does that temp say the engine is running when warmed up? Mine with a 195 T stat runs between 195 and 200*f.
Drain some anti freeze into a clean bucket, to lower level so you can reuse it. Then you will only spill a small amount when removing the T stat.
If your not building pressure? Something is wrong with cap or you have a leak. But I don't see this having anything to do with low temps.
black dawg
1/2 ton status
What does the ecm need to see to set that code?
My tbi 350 wont get up to t stat temp in 10 deg weather unless you work it some. I have messed with stats and nothing has helped. I have decided that it is normal (for mine anyway) and plan on changing the heater core to try and get better heat.
The cooling system probably wont pressurize much if at all in those temps if the fan clutch is cycling.
I have never seen code 15 set even with stuck open stats in 0 deg weather, usually gets set from bad sensor, or ecm grounds at intake.
My tbi 350 wont get up to t stat temp in 10 deg weather unless you work it some. I have messed with stats and nothing has helped. I have decided that it is normal (for mine anyway) and plan on changing the heater core to try and get better heat.
The cooling system probably wont pressurize much if at all in those temps if the fan clutch is cycling.
I have never seen code 15 set even with stuck open stats in 0 deg weather, usually gets set from bad sensor, or ecm grounds at intake.
Error Code 15 can set even if there is nothing wrong!
Code 15 will set if
1. Engine runs for 30 seconds
2. Engine tempresture is less then -22*f for 3 seconds.
So it can set at cold start if outside ambient temps are below -22*f when first started...
Now if you clear the code when temps are above -22*f it should not come back. If it does? The CTS sensor is faulty... which will make it run extremely rich all the time.
If code 15 will only set with the engine -22*f, and the ambient temp is not below that, then there are a few things going on.
The engine temp needs to be verified with a proven accurate temp measuring device. If the engine is actually running at or near rated t-stat temp, your gauge is wrong, and the CTS is bad.
If a PO glued radiator hoses, it's possible/likely the heater core is garbage and part of the reason for no heat, IF the engine is actually getting up to temp.
IIRC, there was a thread not too long ago here(?) about some aftermarket heater cores causing issues because they were made wrong, and allow cold air around the heater core, instead of being forced through it. Keep that in mind as well.
The engine temp needs to be verified with a proven accurate temp measuring device. If the engine is actually running at or near rated t-stat temp, your gauge is wrong, and the CTS is bad.
If a PO glued radiator hoses, it's possible/likely the heater core is garbage and part of the reason for no heat, IF the engine is actually getting up to temp.
IIRC, there was a thread not too long ago here(?) about some aftermarket heater cores causing issues because they were made wrong, and allow cold air around the heater core, instead of being forced through it. Keep that in mind as well.
That code could be old as well? Didn't he have a bad CTS? Usually when the CTS goes bad it reads -40*c and the person is complaining of RICH, Black Smoke, bad running, bad MPG etc...
When my CTS was bad it'd start cold, then after a few minutes puke black smoke and die...unable to re-start til it was cold again.
What is this with setting a code when ambient is below -22 F? Not that we get that cold that often, but probably at least twice a year...so I can expect a SES light and a code set when it does get that cold?
What is this with setting a code when ambient is below -22 F? Not that we get that cold that often, but probably at least twice a year...so I can expect a SES light and a code set when it does get that cold?
