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I service 15 chevy ventures for the local taxi company in town and have become stumped with this one van that has given me trouble over the past few days. At this time I’m doing trying anything I can on my time as I feel bad I’m taking so long to probably figure out a simple issue.
I am servicing this 03 venture with a 3.4 liter motor, dual zone heater, non digital controls, 270000 miles. the vehicle came in blowing warm air, more cold than hot actually. I figured had thought well maybe it was a thermostat and figured that was an easy job as I’ve done so many of them before and cheap as we didnt know the history of this vehicle and when it was last done.
I replaced the thermostat and bled the system with the two bleeders on both sides of the intake until I got a steady stream of fluid and no more air bubbles. Still had just warm air.
I checked the temperature gauge and it was fine and for giggles tested the coolant temp sensor with the multimeter to make sure it was working properly and it was .
I then pressure checked the system and saw no leaks and it held proper pressure not dropping over time at about 20lbs.
I checked the cabin filters and there was none, so I put in 2 new ones, still warm air.
Checked heat at both heater hoses going to the heater core, both were the same temperature at around 142 degrees based off my heat gun reading
I made sure the controls were working properly as in making sure when I switched from defrost to vents and feet ect and all switched as I moved the control. To me this would say the blend door is working fine.
I proceeded to take vehicle for a test drive to see if when I went around corners I would get heat indicating an air pocket in the system and nothing no change.
I flushed the cooing system to the best of my ability without using special products just water and replaced the coolant with 50/50 good to -34 on my tester.
I then tried bleeding system again this time with the front of the vehicle tilted way up on the lift to force the coolant all the way back with chalks under the back wheels as added safety. I did this for about 20 minutes until the car was fully warmed up and then bled with the 2 bleeders on either side of the intake until a steady stream of fluid only came out.
I then topped off the fluid and checked for heat again and nothing but warm air. At times it did seem like I had hotter air than from previous attempts but when I moved the control to say feet only from defrost I would lose whatever hotter air I had and it was back to only warm. This could be just me imagining things maybe im just hopeful or maybe it was a bit warmer who knows lol.
I have never had any issue like this prior and last year when I did 2 of the same ones thermostats it solved this issue and didnt have any bleeding the system problems. I’m not quite sure where to go on this and dont feel like replacing parts that dont need to be replaced. The vehicle has never overheated so I dont think it has to do with a waterpump as it’s not showing any symptoms, nor do I think it’s a plugged radiator for the same reasons even though they may be a bit old and or have some crud in them.
Any thoughts would be great.
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Wow, you’ve done everything. I have purchased bad thermostats out of the box. Maybe replace it with a new one or test the old one in hot water just for kicks? Perhaps it isn’t quite opening all the way…
yeah this one is baffling me. I have even watched youtube videos just to see if what others are doing with these vehicles as far as the cooling system goes and nothing that I already havent done. And as I said I work on these things all the time and never ran into this issue before.
I was thinking well maybe it could be the actual blend door motor aka actuator but it’s switching per control change and the door itself is obviously opening and closing as when I change from cold to hot it does change temp but not to hot just to warm unlike a few weeks ago when they said it was extremely hot for them and then it went to warm only, not even enough to keep the windows defrosted when it’s 10 below up here in maine.
Some have said the resistor could be going bad but I’ve never have seen this as a problem with those symptoms have you?
I had a thermostat go bad and no heat. Checking it against a good one in a pan warming on a stove, the bad thermostat opened first but not by much. Anyway, that was enough to kill the heat.
Another possibility on a vehicle with that many miles is the gasket on the blend door has disintegrated letting cold air bypass the door. See any rubber clunks on the floorboards?
I personally did not see anything on the floor but these things are kept very clean for the customers so if there was anything it was probably vacuumed up before it came to me. I will try another thermostat I guess but I dread doing it again. I say they are easy but thats just cause I’ve done them so many times they are still a bitch pardon my french lol
What was the temperature of the heater hose like in relation to the other coolant hoses on the vehicle? 142F isn’t what I would describe as hot, usually hot is around 180F and cheaper laser thermometers lose accuracy over distance as area they are reading gets larger the further away.
Anyways, Gut that sucker up to operating temp and using a thermometer (not a temp gun) measure the temperature coming out the vent on both sides set to full hot and the fan at about 3/4 as turning it on full will skew the results. Also GMs with dual zone are sometimes helped along the bleeding process by alternating the individual heat controls from full hot to full cold a few times.
Then confirm that you do indeed have some sort of temperature modulation on both sides separately to see if there is any difference from side to side. on like adjustments you should get similar readings. On full hot you should get over 140F coming out the vents, anything lower than 120F and it won’t keep up on a cold day. Unfortuantely this is one of those times that being a number meiser is required as temperature can be subjective and I wouldn’t worry about the difference between the different modes unless you aren’t getting complete switching.
At this point if you still don’t have sufficient heat output and the heater core does not seem clogged you will have to investigate whatever controls the temperature, whether it’s manual or electric and confirming their operation. Odds are though if it still had Dexcool in it the core might be plugged, maybe not even the whole thing. You can always try hooking the heater hoses up backwards.
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