dkp Posted December 17, 2009 Share Posted December 17, 2009 Let's see if my fellow Klipschians can help me solve this issue. Here's the deal: 2002 Chevy Express (full-size) Van; 1/2 ton; V-8 350 Problem: Van was blowing moderately warm air but temp guage was showing at or a hair below the 160 hash. Service engine light on (checked code-says running cooler than normal or something along those lines) What I have done: 1) Replaced thermostat (195 degree failsafe model)-afterwards van still blew moderately warm air (although it did seem a tad cooler than before the replacement but that could simply have been due to a decrease in outside air temp). Guage still reading same, just at/below the 160 hash (it does move) 2) Replaced coolant temp sensor-after change air still blew lukewarm and decreased when van was moving. Guage reading SLIGHTLY higher, barely edged above the 160 hash. 3) Replaced thermostat again (same model)-van now blowing warmer air even when moving (despite frigid MI temps). Guage now about a hash or hash-and-a-half above the 160 mark. Service engine light still on. Van will blow much warmer air even when moving. One other issue that I noticed last night is that the rear air/heat is blowing very cool air. I failed to check this air temp before/after the other changes so I cannot state for certain that this is something new. I cannot imagine what else this could be other than a thermostat. If the coolant temp sensor was bad and indicating a low temp to the guage the air would have been warm. If the guage is bad the air would also still be warm. Any ideas for me? Quote Link to comment Share on other sites More sharing options...
USNRET Posted December 17, 2009 Share Posted December 17, 2009 Blockage in the heater hose return? Are both hoses hot, not then possibly debris in the return hose quick disconnect at the manifold, this QD on some models reduces down to about pencil size or blockage in heater core. Even with a 195 thermostat if outside air temp is frigid the engine won't get up to 'normal' temp. What is past coolant temp at same OAT when the heater was working correctly? Possible water pump impeller errosion not circulating enough water thru heater core. One other thought; does changing the temp control from full hot to cold change the temp of the heater air? If not, or little, the damper door control make be leaking vacuum or inop. Quote Link to comment Share on other sites More sharing options...
dkp Posted December 17, 2009 Author Share Posted December 17, 2009 USNRET: Thanks for the info.! My good buddy who has been helping me through this is a retired navy corpsman. Thanks for your service. Ok, van has been running about 10 minutes now. High hose on driver's side is nice and warm. Lower hose on pass. side is very cool. I'm thinking you're on to something here. I'm going to take it for a drive and get things circulating and then I'll let you know. Quote Link to comment Share on other sites More sharing options...
USNRET Posted December 17, 2009 Share Posted December 17, 2009 Could also be this (heater control valve) http://www.rockauto.com/catalog/raframecatalog.php?carcode=1383926&parttype=6860&a=FRc1383926k887162http://www.rockauto.com/catalog/raframecatalog.php?carcode=1383926&parttype=6860&a=FRc1383926k887162'> Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted December 17, 2009 Share Posted December 17, 2009 OK, let's see. You keep getting a check engine light indicating engine too cold too long. That's usually a thermostat, but you've eliminated that. Your computer looks at the temperature at start up and if it doesn't raise a predetermined ammount in a predetermined time then the code is set. You are also having a heater issue HOWEVER you say you get a temperature increase while driving (more than idle RPM's). We need to find out what these two issues have in common IF they started happening at the same time. I would lean toward a coolant circulation issue. If coolant isn't moving across the sensor or heater cores, you would have both issues. Possible causes? Loose water pump belt. Loose impeller on the water pump shaft. Worn vanes on the water pump (yes, it can happen). It's possible that you have a restriction some where, but typically water pumps have bypasses that will allow some circulation, so I think I'd check that last. Carl Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted December 17, 2009 Share Posted December 17, 2009 In addition, your rear heater core is farthest from the pump and would suffer the worst from a circulation problem. Also if one core, or hose to a core was restricted, the other one should heat up. Quote Link to comment Share on other sites More sharing options...
dkp Posted December 17, 2009 Author Share Posted December 17, 2009 Just got home. Van has been running for a little over an hour now. I drove it about 15 miles (had lunch w/my mom). Got home, same deal. Upper hose connected to the radiator on the driver's side is very warm. Lower hose on pass. side is pretty cool. The warm air coming out of the vents feels about right, very nice and warm. However, back is still cool, except one vent has lukewarm air coming out. I left the van running while I had lunch and when I came out noticed that the guage read about 195 degrees. As soon as I started moving it dropped a fair amount, maybe to 172 or so, but the warm air stayed warm. I admit that I have not watched the temp guage too closely in the past so I cannot state for certain that that much of a drop is normal. Outside temp today is 23 degrees. I am going to remove the battery terminal for a half-hour or so to see if that resets the engine light. Will keep you posted and thanks for the help. Quote Link to comment Share on other sites More sharing options...
dkp Posted December 17, 2009 Author Share Posted December 17, 2009 OK, let's see. You keep getting a check engine light indicating engine too cold too long. That's usually a thermostat, but you've eliminated that. Your computer looks at the temperature at start up and if it doesn't raise a predetermined ammount in a predetermined time then the code is set. You are also having a heater issue HOWEVER you say you get a temperature increase while driving (more than idle RPM's). We need to find out what these two issues have in common IF they started happening at the same time. I would lean toward a coolant circulation issue. If coolant isn't moving across the sensor or heater cores, you would have both issues. Possible causes? Loose water pump belt. Loose impeller on the water pump shaft. Worn vanes on the water pump (yes, it can happen). It's possible that you have a restriction some where, but typically water pumps have bypasses that will allow some circulation, so I think I'd check that last. Carl Carl-I was getting a temperature decrease when driving. That issue seems to have resolved itself. Quote Link to comment Share on other sites More sharing options...
dkp Posted December 17, 2009 Author Share Posted December 17, 2009 In addition, your rear heater core is farthest from the pump and would suffer the worst from a circulation problem. Also if one core, or hose to a core was restricted, the other one should heat up. I'm thinking the issues with the front and rear are distinct from one another. We had an issue with the rear heat/cooling some time ago and had to have some work done. If memory serves, I believe he simply flushed it out but I may be way off on that. I'm going to take it in this afternoon to have the rear hear issue addressed. I'm thinking it may have some air in the line back there which would be more difficult to get out. Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted December 17, 2009 Share Posted December 17, 2009 OK, let's see. You keep getting a check engine light indicating engine too cold too long. That's usually a thermostat, but you've eliminated that. Your computer looks at the temperature at start up and if it doesn't raise a predetermined ammount in a predetermined time then the code is set. You are also having a heater issue HOWEVER you say you get a temperature increase while driving (more than idle RPM's). We need to find out what these two issues have in common IF they started happening at the same time. I would lean toward a coolant circulation issue. If coolant isn't moving across the sensor or heater cores, you would have both issues. Possible causes? Loose water pump belt. Loose impeller on the water pump shaft. Worn vanes on the water pump (yes, it can happen). It's possible that you have a restriction some where, but typically water pumps have bypasses that will allow some circulation, so I think I'd check that last. Carl Carl-I was getting a temperature decrease when driving. That issue seems to have resolved itself. I meant that you were getting an increase in heater temp, not engine temp. I wasn't clear. I still believe the engine too cold too long is the root symptom. Find that issue and the rest may be fixed. Any stoppage in the radiator or heater core will not cause this issue. If anything, just the opposite. Quote Link to comment Share on other sites More sharing options...
USNRET Posted December 17, 2009 Share Posted December 17, 2009 Upper hose connected to the radiator on the driver's side is very warm. Lower hose on pass. side is pretty cool. These are the radiator to engine feed and return hoses, not the heater hoses. The water leaves the radiator from the bottome and circulates thru the engine (and heater) and then returns to the radiator thru the upper hose/ I suspect water pump as one issue. Quote Link to comment Share on other sites More sharing options...
JL Sargent Posted December 17, 2009 Share Posted December 17, 2009 First off, I drive a 1Ton Chevy van with the same motor. I have never had a problem with it being too cold and all kinds of trouble keeping it down to 195 ! Engine too cold at 165 F. You have a 195 stat and it should be close to that. A simple contact or IR thermometer can verify actual engine temp. Try another temp. measuring method and find out your real temperature. Water pump problems are indicated by a motor thats TOO HOT not too cold. Is the thermostat installed backwards? Your air handler is controlled by vacuum. These van type vehicles are prone to get hot and cut these vacuum lines. This will make the air handler not work properly and therefore not deliver heating/cooling air to the cabin. Inspect the air handler control vacuum line from the carb to the air handler control in your dash. Quote Link to comment Share on other sites More sharing options...
JJkizak Posted December 17, 2009 Share Posted December 17, 2009 Check the little tiny hole in the thermostat---it should be facing up. It will not work properly if the hole is not facing up. Also bleed the cold hoses as sometimes air pockets develope and they are murder to try and bust them out, especially after the rear system was flushed. Next the air conditioning system has a control solenoid valve that will shut off the coolant flow to the heater core when the AC system is activated.This valve may be stuck. If your coolant temperature is actually running at 160 the computer will not get out of the start up mode (rich) and you will be chucking gas out the window. Also check to see that your lower radiator hose to the coolant pump isn't collapsing when running. Lastly, You pissed somebody off who is a "Voodo" professional and he has a pin stuck in a model of your vehicle to get back at you. The most likely scenario is an "air pocket". If your desparate put on a set of 4 tube headers, I garuntee your engine will run hot. JJK Quote Link to comment Share on other sites More sharing options...
mark1101 Posted December 18, 2009 Share Posted December 18, 2009 Are you running the correct "mix" of antifreeze to water? If you are running pure antifreeze that may be the problem. Quote Link to comment Share on other sites More sharing options...
dkp Posted December 19, 2009 Author Share Posted December 19, 2009 Evidently third times a charm. We changed out the thermostat again this time using a Delco product. I'm pretty sure it wasn't the thermostat itself but rather the gasket that was creating these issues. The gasket has a groove on the inside that seats the thermostat. Unfortunately, we didn't realize this and had simply been placing the gasket on top of the thermostat. I'm guessing that our method of installation did not provide a good seal and coolant was then bypassing the thermostat. So we changed both the brand of product being used and put the gasket on the right way and things are working properly now. I took the van in to get the rear heater core flushed out and will be picking it up this morning. Thanks for all of the help. I posted this on two automotive forums before posting here and my Klipsch buddies came through first! Nice job, guys!! Quote Link to comment Share on other sites More sharing options...
JL Sargent Posted December 19, 2009 Share Posted December 19, 2009 Do what? I hope you learned a valuable lesson. Don't drink beer while replacing the thermostat gasket. Quote Link to comment Share on other sites More sharing options...
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