Seeking knowledge regarding HVAC system. initial symptom little or no heat. I have experienced this before with a 90 olds cutlass supreme. I noticed that the engine temp wasn't getting much higher tht 160 degrees so I replaced the following parts. Bought and A/C Delco water pump, thermostat and thermostat housing as well as A/C belt and fan clutch. All the parts replaced were original hence the reason ll the above got changed. Filled the cooling system, got the car up to temp and the gauge is now reading the normal temp, no leaks. Still very marginal heat so I then pulled the HVAC fuse figuring the blend door actuator needed to be reprogrammed. Still very marginal heat. So after searching the net and seeing much info coming from this forum I joined. I learned that the oem plastic quick disconnects like to fail so I plan on replacing all the hoses with the droman hoses with upgraded aluminum fittings. I figure why wait until I break down. I do have rear heat and A/C. I am under the impression that the heater cores need to be flushed and I keep hearing and reading the flush should be done in the opposite direction of flow, through the return lines. This is y question, is the supply line the black plastic fitting/hose or the white fitting/ hose???? Also does anyone know the pipe diameter of the actual heater core pipes, I ask because I plan on getting some clear vinyl hose to use for the flush. Thanks in advance. I will be asking a few more question under new threads.
04 Yukon SLT
- Thread starter 82nd Abn
- Start date
Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.
It will help us to know what you're working on (I know it's in this thread title). Consider putting some vehicle info in your forum signature so it's always there. Year, make, model, engine, etc.
Check the free www.charm.li site for detailed repair info.
Check the free www.charm.li site for detailed repair info.
Last edited:
My apologies, It is a 2004 Yukon SLT with a 5.3 liter engine with rear heat and ac. I will work on your suggestion now.
I would flush the heater core both ways.
The www.charm.li site can be helpful for all sorts of info.
The www.charm.li site can be helpful for all sorts of info.
Thanks that is what I will do. I tried to update the signature and was unable to save it. I will try again.
Excellent! The signature update worked.
If you happen to be using a phone, turn it sideways (landscape mode) to see signatures.
If you happen to be using a phone, turn it sideways (landscape mode) to see signatures.
- Joined
- Aug 2, 2018
- Posts
- 10,285
- Reaction score
- 14,892
Welcome to the Forum from NH.
Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.
I hope that you will become a participating member in the Forum's discussions.
Pics of the truck, please.
You are already receiving sage advice from the knowledgeable folks on this Forum.
There are a number of blend doors on these trucks, and I believe that your issue is a malfunctioning blend door, and not a clogged front heater core (unless you tell me that you had really, really, really deteriorated/corroded coolant, when you changed it). You need to test the operation of all of your blend doors, before you start randomly disassembling and/or flushing things, IMO.
@swathdiver can lend in his knowledge and perspective on your issue and give you some suggestions regarding troubleshooting blend door operations.
For the future:
Do you have, or have access to, a quality bi-directional scanner? If not, I recommend that you get yourself a quality bi-directional scanner to add to your tool box. Then, you will be able to read ALL trouble codes, along with a brief explanation/pointer to the source of your issue. You can test many of the truck's electronic functions with the scanner, in order to determine the source of an issue. You will also be able to reset/delete trouble codes, after taking corrective action. You will literally save thousands of dollars in diagnostic and repair costs over the life of your truck, and you will most likely recoup the cost of the scanner within 1 year.
You can fully test the operation of all blend doors with a quality bi-directional scanner.
Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.
I hope that you will become a participating member in the Forum's discussions.
Pics of the truck, please.
You are already receiving sage advice from the knowledgeable folks on this Forum.
There are a number of blend doors on these trucks, and I believe that your issue is a malfunctioning blend door, and not a clogged front heater core (unless you tell me that you had really, really, really deteriorated/corroded coolant, when you changed it). You need to test the operation of all of your blend doors, before you start randomly disassembling and/or flushing things, IMO.
@swathdiver can lend in his knowledge and perspective on your issue and give you some suggestions regarding troubleshooting blend door operations.
For the future:
Do you have, or have access to, a quality bi-directional scanner? If not, I recommend that you get yourself a quality bi-directional scanner to add to your tool box. Then, you will be able to read ALL trouble codes, along with a brief explanation/pointer to the source of your issue. You can test many of the truck's electronic functions with the scanner, in order to determine the source of an issue. You will also be able to reset/delete trouble codes, after taking corrective action. You will literally save thousands of dollars in diagnostic and repair costs over the life of your truck, and you will most likely recoup the cost of the scanner within 1 year.
You can fully test the operation of all blend doors with a quality bi-directional scanner.
WHat scanner do you recomend? I also have an 01 WJ would it have the capability to work on both vehicles? That is one heck of a nice vehicle you built!!!!!!!
I may be wrong regarding the need to flush the two heater cores but my gut is sending me in that direction. The logic? when I am not at idle more heat comes out of the vents hence why i feel it is a flow problem. Yes hen I popped the lower hose to facilitate changing the water pump the fluid had an orange tint to it and I did see some rusty water. I did pull the HVAC fuse in the hopes that the blend doors recalibrated. I heard them move(no clicking). I do want to be preemptive and change the hoses before the inevitable so while I have them off the cores will be flushed.
I believe that a 5/8" ID hose should work for flushing.
Recalibrating the blend and mode doors by pulling the fuses doesn't always work well, at least in my experience. Doing the reset with a capable scanner (as recommended by @Joseph Garcia) is the preferred method.
My son and I use an Autel MaxiPRO MP808S-TS, but that one runs close to $1k (one of the reasons I got that one is that is also initializes TPMS sensors). You might need to just find someone nearby with a good scanner to see what the HVAC doors show as to commanded position vs. actual position. Check the thread that shows the owners of GM Tech 2 scanners for help with your GM:
www.tahoeyukonforum.com
The capable Autels start probably around $500 or so and would be able to handle both your vehicles, but check the specs when you do your shopping. Other brands are available so check reviews. Ivan at Pine Hollow Auto Diagnostics does occasional comparisons, so check that YouTube site (https://www.youtube.com/channel/UCn4Ifss-t3wMT6VBzQoKPUA) for video reviews.
Recalibrating the blend and mode doors by pulling the fuses doesn't always work well, at least in my experience. Doing the reset with a capable scanner (as recommended by @Joseph Garcia) is the preferred method.
My son and I use an Autel MaxiPRO MP808S-TS, but that one runs close to $1k (one of the reasons I got that one is that is also initializes TPMS sensors). You might need to just find someone nearby with a good scanner to see what the HVAC doors show as to commanded position vs. actual position. Check the thread that shows the owners of GM Tech 2 scanners for help with your GM:
Tech 2 Owners Map
There are quite a few members that have a Tech 2 and there are always people who wish they had one to use so I thought I would post this thread to try and help each other out. If you own a Tech 2 and would be willing to help out another forum member that might be local to you then post up your...
www.tahoeyukonforum.com
The capable Autels start probably around $500 or so and would be able to handle both your vehicles, but check the specs when you do your shopping. Other brands are available so check reviews. Ivan at Pine Hollow Auto Diagnostics does occasional comparisons, so check that YouTube site (https://www.youtube.com/channel/UCn4Ifss-t3wMT6VBzQoKPUA) for video reviews.
- Joined
- Aug 2, 2018
- Posts
- 10,285
- Reaction score
- 14,892
Thank you for your compliment on my truck build. Lots of money spent on it, but also lots of smiles per mile driving it. It is the street beast that I never could afford during my entire working life. I decided on a truck to mod, because at my age, if I modded a street performance car, I'd likely kill myself racing it around.
Changing out your coolant and ALL hoses and Tees is a great preventive maintenance procedure. I had one hose burst on me, as the hoses were original. Fortunately, I was very close to home and was able to limp back there.
A China knockoff Tech 2 quality bi-directional would be ideal for your truck, but it probably won't work on your WJ. As @Fless suggested, an Autel scanner would be ideal for you with multiple vehicles. The Autel scanner listed in my Signature cost about $500 from Amazon, and it will do just about anything that I could imagine for basic and advanced troubleshooting.
I am almost 62, over 100 years ago after getting out of the Army after nine years I went to college to become a commercial pilot however I had to sell my 74 stingray and my harley to pay for the last year. I vowed to one day replace both. I have had the harley since 2011 this coming year I will buy the corvette. I have cheated death 7 times mostly while in the army. I will probably spend more time turning wrenches on it and cleaning it than driving it. I am not adverse to spending money on tools rather than the cost of labor at a shop. Thank you for the suggestion!!!!! My cousin over in TN has one and swears it is the best thing since sliced bread.
Thank so much!!! I will check out that thread and see about buying a tool that will work on both. I had no clue they were capable of doing such a test. I love new gadgets!I believe that a 5/8" ID hose should work for flushing.
Recalibrating the blend and mode doors by pulling the fuses doesn't always work well, at least in my experience. Doing the reset with a capable scanner (as recommended by @Joseph Garcia) is the preferred method.
My son and I use an Autel MaxiPRO MP808S-TS, but that one runs close to $1k (one of the reasons I got that one is that is also initializes TPMS sensors). You might need to just find someone nearby with a good scanner to see what the HVAC doors show as to commanded position vs. actual position. Check the thread that shows the owners of GM Tech 2 scanners for help with your GM:
Tech 2 Owners Map
There are quite a few members that have a Tech 2 and there are always people who wish they had one to use so I thought I would post this thread to try and help each other out. If you own a Tech 2 and would be willing to help out another forum member that might be local to you then post up your...
The capable Autels start probably around $500 or so and would be able to handle both your vehicles, but check the specs when you do your shopping. Other brands are available so check reviews. Ivan at Pine Hollow Auto Diagnostics does occasional comparisons, so check that YouTube site (https://www.youtube.com/channel/UCn4Ifss-t3wMT6VBzQoKPUA) for video reviews.
