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Greg Cuetara
09-20-2009, 9:42 AM
I have a '99 Chevy Blazer which has treated me very well over the last 10 years. It has about 120k and I have done almost all the regular service up to this point in time.

The Blazer has been relegated to heavier tow duty and plow duty in the winter time. I think I don't have 500 miles in the past year on the truck.

About 2 years ago I had a problem with the heat and the dealer said the heater core was shot. It is about 12 hours to replace because it is behind everything else...only about a $100 part though. The labor adds up pretty quickly and puts the fix out of reach for me right now.

I had the whole system backflushed and it seemed to fix the problem and I got heat back. I went out this weekend for a trip and didn't have any heat. Not very fun to drive a few hundred miles with no heat on a cold day and not looking forward to plowing this winter with no heat.

I was told to get the radiator flushed and that might help but not sure if it will.....I don't think I have ever had it flushed so it might be wise anyways.

I was also trying to figure out an alternative...like a 12v space heater that I could plug in while I was plowing I could turn it on to just take the chill off the air. Anyone have any suggestions for heaters or other things I can try to do which might give me heat back.

Thanks,
Greg

Stephen Reid
09-20-2009, 10:08 AM
I feel your pain!The same thing happened to me on a full size chev pick up.But my heater core was leaking and had to be replaced.Major job basicly have to unbolt the entire dash to change it out.Did it my self but it took a full weekend.If yours is not leaking I would try back flushing again and do the rad too you might have some crap in there and it will get into the heater core.Also replace your thermostat it might be stuck open.Definate cause of no heat and only a $10 part.Good pm too as they can stick shut too and overheat your engine.Good luck

Steve Rozmiarek
09-20-2009, 10:56 AM
Stephen nailed the most common problem, which is easy to check for, just see if your engine is running a consistant 190 or so, or if the temp is moving around radically, you need a thermostat. As Stephen said, cheap preventative maintinance.

Pat Germain
09-20-2009, 11:00 AM
You can often unplug a heater core yourself by removing the heater hoses from the core and connecting a garden hose. Find out which end of the core is "IN" and connect the hose to the other side. That's right, run the water through the core backwards. This will help to purge whatever is clogging the core. Be aware that in an older vehicle, doing this can also run the risk of creating a leak in the core. Also:

- It would be a very good idea to have the cooling system flushed

- When the system is flushed, the thermostat should be replaced

Nothing will work nearly as well as the onboard heater. It's worthwhile to get it fixed if you plan to keep the truck. Heat good!

Pat Germain
09-20-2009, 11:05 AM
Stephen nailed the most common problem, which is easy to check for, just see if your engine is running a consistant 190 or so, or if the temp is moving around radically, you need a thermostat. As Stephen said, cheap preventative maintinance.

Oh yeah, good point. Modern thermostats are designed to fail in the "open" position. While that's better than sticking closed and overheating the engine, it's still not good. Not only will an open thermostat keep the heater from working properly, it will cause the engine to run too cold. A cold running engine uses more fuel, doesn't perform as well, creates sludge in the crankcase, wears out prematurely and promotes rust throughout the cooling system. (When I lived in the South, many a redneck would remove the thermostat from his vehicle thinking it was good to make the engine run cold. Not surprisingly, they were blowing blue smoke out the tailpiple not long thereafter.)

It would be a good idea to replace the thermostat as your first step. Get a good NAPA thermostat. They run around $10.

Steve Schlumpf
09-20-2009, 11:07 AM
Greg - I have a 97 S10 and had problems with heat also.

Found out that there were a few years that Chevy went with some alternative type of antifreeze that eventually caused blockages in the system. I lost heat and took my truck in for service. They flushed the system. Worked for about a week. Flushed it again - worked for another week. Took it back in (not happy this time!) - they flushed the system in 3 separate stages - block, radiator and heater core - filled with fresh 'real' antifreeze and also changed out the thermostat. Has worked ever since.

Talking to the service manager during this process that Chevy had put out a service notice for all those vehicles that had this new type of antifreeze - to flush the systems and replace with the real stuff. Seeing as how you have basically the same vehicle - this would be worth considering as it took them 3 times to flush the system to get all the blockages out.

Joe Pelonio
09-20-2009, 11:19 AM
I don't know what it is about Chevy and heater cores. I have replaced 5-6 of them on various cars over the years, the worst was a 1964 Chevelle, had to remove the front fender! The others, including the '72 El Camino were pretty easy.

JC Whitney has electric heaters that will help if you don't find another solution.

George Lesniak
09-20-2009, 11:48 AM
Greg,

As Steve mentioned GM has been using an anti-freeze called Dexcool which has a tendency to gel and restrict the flow through the heater core. To help determine if this is the problem first look into the coolant reservoir. Are there lumps of "orange jello" in there? If so the cooling system does need to be flushed. Now, with the engine running and fully warmed-up, feel the heater hoses. is one hot and one cool? If so, the heater core is plugged. When the engine is flushed they will need to flush the heater core separately or they run the risk of sending all the contaminated coolant from the engine into the heater core and compounding the problem. make sure they use a good flush chemical, not just water, to dissolve the gelled Dexcool.

If both heater hoses are both hot, indicating flow in and out of the core, you may have a blend door or mode door issue inside the vehicle.

If the thermostat were stuck open and the engine was running at 180° instead of 220° you would still have some heat just not full heat. Try switching the temp control from full cold to full hot while holding your hand in front of the heater duct. If you feel a noticeable increase in duct temperature but it just isn't hot enough, look to the thermostat.

George

Scott T Smith
09-20-2009, 11:51 AM
Lots of good advice offered thus far. I too have swapped out several heater cores, and if yours is not leaking I would pursue other options.

In addition to the flushing, new thermostats, etc that have already been suggested, you should also check to make sure that you don't have a "heater control valve" somewhere in your system. These regulate the flow of coolant to the heater core (shutting them off so that you don't have hot water inside the car during the summer), and often times they are vacume operated. When the vacume damper goes bad, the valve won't open... Also, sometimes they will corrode shut.

Based upon your description of the truck, if a replacement valve is too expensive you can either bypass it or put in a manual valve (like all of my tractors have). Open it at the beginning of winter, and shut it in the spring.

Brent Leonard
09-20-2009, 5:26 PM
Harbor Freight has an inexpensive 12v electric heat/fan.

Until you can FIX the problem, the 12v heater will work and get you by.
Be smart in regard to fires and leaving the heater unattended.

Scott T Smith
09-20-2009, 5:46 PM
Greg,

As Steve mentioned GM has been using an anti-freeze called Dexcool which has a tendency to gel and restrict the flow through the heater core. To help determine if this is the problem first look into the coolant reservoir. Are there lumps of "orange jello" in there? If so the cooling system does need to be flushed. Now, with the engine running and fully warmed-up, feel the heater hoses. is one hot and one cool? If so, the heater core is plugged. When the engine is flushed they will need to flush the heater core separately or they run the risk of sending all the contaminated coolant from the engine into the heater core and compounding the problem. make sure they use a good flush chemical, not just water, to dissolve the gelled Dexcool.

If both heater hoses are both hot, indicating flow in and out of the core, you may have a blend door or mode door issue inside the vehicle.

If the thermostat were stuck open and the engine was running at 180° instead of 220° you would still have some heat just not full heat. Try switching the temp control from full cold to full hot while holding your hand in front of the heater duct. If you feel a noticeable increase in duct temperature but it just isn't hot enough, look to the thermostat.

George


It's always nice when a professional chimes in! Good advice, George.

Scott

Greg Cuetara
09-20-2009, 9:09 PM
wow. Thanks for all the advice. I kept checking the temp in the truck yesterday and it was a steady 200-210 all day. That is just about right in the middle of the dial.

I tried switching it between hot and cold and there is a difference but no heat...it is cold just not as cold.

I just did a google search for dexcool and it looks like there was a class-action lawsuit over it that it really screwed up a lot of vehicles....mostly the gmc jimmy, chevy blazer and s10 pickup. That was before bankrupcy so I assume I can't get anything right now.

I guess it is off to the dealer to get everything flushed. Hopefully it doesn't cost me too much.

Greg

George Lesniak
09-20-2009, 10:28 PM
wow. Thanks for all the advice. I kept checking the temp in the truck yesterday and it was a steady 200-210 all day. That is just about right in the middle of the dial.

I tried switching it between hot and cold and there is a difference but no heat...it is cold just not as cold.

I just did a google search for dexcool and it looks like there was a class-action lawsuit over it that it really screwed up a lot of vehicles....mostly the gmc jimmy, chevy blazer and s10 pickup. That was before bankrupcy so I assume I can't get anything right now.

I guess it is off to the dealer to get everything flushed. Hopefully it doesn't cost me too much.

Greg

Greg,

You can easily do this yourself, it's not hard. Just head off to a quality parts store like, I don't know, CARQUEST, and get a flush kit and chemical. It shouldn't be more than $10-$15. Run the chemical in the cooling system for a good 30 minutes or so and flush it out with a garden hose. Make sure to flush through the heater core in both directions.

George

Paul Ryan
09-20-2009, 10:50 PM
Greg,

You can easily do this yourself, it's not hard. Just head off to a quality parts store like, I don't know, CARQUEST, and get a flush kit and chemical. It shouldn't be more than $10-$15. Run the chemical in the cooling system for a good 30 minutes or so and flush it out with a garden hose. Make sure to flush through the heater core in both directions.

George

I 2nd George's recommendations. It is not hard to flush your cooling systems. But be sure to take the hoses off the heater core and flush with hot water if you can, it will loosen up any left over crap that is in there that the chemical loosened up. I suspect you will get some heat after that, good luck. While you are at it, clean out your over flow so you don't get that garbage back in the system.

Chris Damm
09-21-2009, 8:27 AM
Is your coolant level high enough. Low coolant levels will cause the heater problem you are having. DAMHIK

Greg Cuetara
09-21-2009, 12:26 PM
I will say that I am mechanically inclined but not so much with cars. $15 bucks is going to be much better than going to a shop to get it done...yet another project I don't have time for right now :)

Chris I did check my coolant level and it is the orange stuff...didn't see any clumps in it but i could barely see it. It was at the bottom of the plastic reservoir. I questioned the dealer about this once and he said that it was at the correct level but who knows if that is right or not.

Again thanks. I will looking into seeing if I can flush it out myself.
Greg

Chris Damm
09-22-2009, 8:19 AM
Check the level in the radiator. The line between the radiator and plastic reservoir is easily plugged.

Pat Germain
09-22-2009, 8:35 AM
The effectiveness of a home cooling system flush is limited. It will keep a functioning system functioning. But it may not solve this problem; especially considering it involves the troubled GM antifreeze.

Some shops will simply connect a large bottle of coolant to the truck and start it. As the water pump turns, it sucks in the new coolant and pushes out the old coolant. This replaces the coolant, but not much else.

A good coolant system flush uses a pressurized machine. The coolant is drained and the truck is connected to the machine. The machine pumps a chemical solution back and forth through the entire cooling system with significant pressure.

I suspect the latter method will be required to get the heater core working again. And, most importantly, keep it working! So, if it's in the budget, I would recommend having a professional system flush. It will be money well spent come mid-December. You don't want to have to mess with your cooling system again when it's below freezing outside. :)

George Lesniak
09-22-2009, 10:17 AM
The effectiveness of a home cooling system flush is limited. It will keep a functioning system functioning. But it may not solve this problem; especially considering it involves the troubled GM antifreeze.

Some shops will simply connect a large bottle of coolant to the truck and start it. As the water pump turns, it sucks in the new coolant and pushes out the old coolant. This replaces the coolant, but not much else.

A good coolant system flush uses a pressurized machine. The coolant is drained and the truck is connected to the machine. The machine pumps a chemical solution back and forth through the entire cooling system with significant pressure.

I suspect the latter method will be required to get the heater core working again. And, most importantly, keep it working! So, if it's in the budget, I would recommend having a professional system flush. It will be money well spent come mid-December. You don't want to have to mess with your cooling system again when it's below freezing outside. :)

I'm sorry Pat but I must disagree with a few points you make. First, the "professional" cooling system flush machines come in two categories: with internal pump and without. The machines with an internal pump are either air powered or have an on-board electric pump, neither of which will typically exceed 12-15 psi. (normal cooling system pressure) The machines without an on-board pump are powered my water pressure, just like using a hose, but have a regulator to step the pressure down to less than 15 psi. The real benefit of the professional units is the flush chemical which is almost always more potent than what is available to the retail consumer. The flush chemical is added to the vehicle cooling system, never to the flush machine, and the engine is run circulating the chemical throughout the cooling system. The machine is only used to exchange the dirty coolant for new clean coolant. Also, no professional cooling system flush machine can flush "back and forth", they either flush in the normal direction of coolant flow or reverse flow; which is preferred for contaminant removal. Either way, the machine pumps in new coolant to force the old coolant out. When the coolant returning to the machine is clean the service is done, leaving gelled Dexcool in the cooling system unless the service is repeated several times. Very rarely is a flush machine successful at removing gelled Dexcool from a heater core. The technician almost always has to flush the core manually with a water hose and sometimes with the aid of air pressure, alternating with and against the normal flow of coolant until most of the debris is removed. One real benefit to the DIY method is, by installing the flushing tee into the heater core the user can direct the flow of coolant in either direction, kind of like the "back and forth" method you described. Professional machines have moved away from the heater hose tee and toward the radiator hose making the service more of an exchange than a flush.

George

Paul Ryan
09-22-2009, 3:59 PM
I'm sorry Pat but I must disagree with a few points you make. First, the "professional" cooling system flush machines come in two categories: with internal pump and without. The machines with an internal pump are either air powered or have an on-board electric pump, neither of which will typically exceed 12-15 psi. (normal cooling system pressure) The machines without an on-board pump are powered my water pressure, just like using a hose, but have a regulator to step the pressure down to less than 15 psi. The real benefit of the professional units is the flush chemical which is almost always more potent than what is available to the retail consumer. The flush chemical is added to the vehicle cooling system, never to the flush machine, and the engine is run circulating the chemical throughout the cooling system. The machine is only used to exchange the dirty coolant for new clean coolant. Also, no professional cooling system flush machine can flush "back and forth", they either flush in the normal direction of coolant flow or reverse flow; which is preferred for contaminant removal. Either way, the machine pumps in new coolant to force the old coolant out. When the coolant returning to the machine is clean the service is done, leaving gelled Dexcool in the cooling system unless the service is repeated several times. Very rarely is a flush machine successful at removing gelled Dexcool from a heater core. The technician almost always has to flush the core manually with a water hose and sometimes with the aid of air pressure, alternating with and against the normal flow of coolant until most of the debris is removed. One real benefit to the DIY method is, by installing the flushing tee into the heater core the user can direct the flow of coolant in either direction, kind of like the "back and forth" method you described. Professional machines have moved away from the heater hose tee and toward the radiator hose making the service more of an exchange than a flush.

George

George said it best. The professional coolant flushers are basically a coolant exchanger. What does the removal of the crud in the system is the chemical. The best thing to do is to put the chemical in your cooling system and drive it for 25-50 miles. Let it get good and mixed in there an loosen up the crap. But as George stated more than likely to get heat to come out of your heater core you will need to flush it maually. Pull both hoses and flush hot water both directions and blow compressed air in there to, that should get heat going again. But if you don't flush out the rest of the system that crap will end up in the heater core again. By the way when you drain your system don't use the drain cock at the bottom of the radiator. The hole is too small and can clog with the crap that comes out. The best method it to pull your bottom hose off the radiator, but be prepared the coolant will be hot, where gloves and, a jacket to protect your arms.

If you are mechanically inclinded at all you can save yourself $100+ by flushing the system yourself. The only thing the professional machines do, is save us mechanics time when you bring the vehicle to us.

Pat Germain
09-22-2009, 7:00 PM
I'm sorry Pat but I must disagree with a few points you make.

Well, serves me right for listening to Pat Goss on "Motorweek". I typically flush the cooling system on my vehicles myself. Once again, when I assume a pro can do a much better job, it's probably not the case.

Greg Cuetara
11-21-2009, 5:37 PM
Folks. Thank you to everyone and their advice. I was finally able to flush my cooling system and radiator today. I had a friend come over and help...guess I thought that two people who know nothing about cars is better than one. Anyways It took us over an hour to finally find and get the radiator drain open and drain the whole system. We installed the prestone flush kit and backflushed the heater core then put in the prestone solution to break down and clean out the radiator. Ran the car for 10 minutes and then flushed the system again. Put in regular prestone antifreeze / coolant 50/50 mix and it seems like I now have heat. I just hope that it stays or I will be flushing the system again. I hooked the garden hose up to the washer outlet so that i was putting hot water into the engine rather than cold water typically coming out of the tap.

So now my only question is how much coolant do I need to put back in? I was able to put in 1 gallon of coolant. About 90% of that directly into the radiator and the rest into the reservoir. If I read the book correctly it says the coolant system takes 11.7 quarts which comes out to almost 3 gallons. Do I just need to run the truck for a while to burp the system and keep adding coolant until I get to the 11 quarts?

Thanks again much better to spend $20 and an afternoon rather than $500 in the shop.

Greg

Tom Godley
11-21-2009, 8:05 PM
You normally want a 50/50 mix.

After a flush all you are going to have in the system is water.

I normally open the drain (if it has one) and remove enough water so I can put in the total amount of coolant into the system and then fill it the rest of the way with water. That way I know I have the 50/50 mix

Make sure you save some antifreeze for the overflow tank so it is 50/50 -- don't risk filling it with plain water on a cold night -- it can take a long time for that water to mix into the system.

And yes often you must top off the system after it runs for a while.

Greg Cuetara
11-21-2009, 8:07 PM
Tom, thanks. I used a 50/50 prestone mix. I figured it was just easier to use the premixed stuff and the fact that my dad gave it to me helped out a bit.

Greg

Paul Ryan
11-21-2009, 8:36 PM
Greg,

If you only got 1 gallon of premixed in more than likely you have a air bubble in the system. There are 2 ways to remove it. Gently take off the upper hose (or either right or left if it is side by side) and fill the system untill coolant comes out the hose. Then run it with the radiator cap off until the t-state opens, upper rad hose will get hot, and then top it off and fill the over flow half. Or drive it and top off the over flow if it drops. The latter doesn't work as often and the air bubble maybe stay in the system. No there is a possibility you have straight water in the system now after the flush. I would but about 1/4 gallon straight anti freeze in to mixed with the water. If you dont have water in the system it will just strenghten your mix.