This past couple of weeks, my heat has stopped working in my 98 Blazer. does anybody have an idea what it may be? And it is -2F in Massachussetts right now!

This past couple of weeks, my heat has stopped working in my 98 Blazer. does anybody have an idea what it may be? And it is -2F in Massachussetts right now!


Ooooh I might be able to help you!

I've had the same problem, my heat will not work, however, watch your engine temperature guage. When it gets to 3/4 max, turn your heat off and on, or turn your car off and on. Your heat should kick in and your engine temperature will drop below half.

This is a problem I've been experience on my Blazer, not a problem, but a huge nuisance. There might be an easier way, but most of the time I can just turn the heat off, then turn it back on 5 seconds later.

Had the same problem with my 99 Blazer. Had the Heater core flushed. Heat will now blow you out of the truck. :)

Have the heater core flushed. The dexicool builds up and starts to block stuff. When mine was flushed big chunks came out. It's a known issue with blazer's. Maybe check the thermostat too. That's only $7-8 to replace.

when you are flushing your heater core, do you use just a simple garden hose or should the water be somewhat pressurized?

Can some give me the details on flushing the heating core?

garden hose works fine

in my 98 blazer my heat would run u out of the damn thing when i bought it but now it will freeze you out of the truck. any ideas???? it was sudden not slow i don't believe the core clogged that quick.... i have the computer climate control system

Check your fluid level and then try flushing the core. It is an easy fast cheap process and it worked for me.

After driving to my local Napa Store and getting a new thermostat for my 1998 Chevy Blazer that had no heat even though it was heating up and staying at about 180f. I came home and put it in my garage, my brother is a mechanic and that is what we do for a living is repair cars, Took about 10 mins to get the two bolts out on the top remove the old one and put the new one in. After about 25mins of messing around with the back bolt trying to get it to go in as it kept fetching up, i just gave it some more leverage and tightened it up. that started it and it had heat so i figured it was fixed, me and the old lady went to walmart and the heat started blowing ice, it is currently 8 degrees out. so I came back, dropped her off at the house, and went back to the garage with it, I removed both heater lines off the heater core on the firewall, and took a short piece of heater hose, and the air line, and sent 120psi of air through the core for about 10mins, big chunks of hard DEX-COOL came out, I than put both lines back on and re clamped, and started the engine, the heat will now LITERALLY cook me out.. i recommed you blow out the heater core with either a garden hose or do as i did with an air line

I had this problem last winter. My brother was able to blow out the line with high pressure air and gobs of dex-cool did come out. It worked great for a couple of months and then he had to do it again and then one more time. I haven't had the problem this winter.

I did the garden hose method. Worked perfectly!

Here is a posting I made in a similar thread. It should help diagnose and provide some solutions and answers.

1. How do I tell if my heater core is plugged?
Answer: with the car running warm feel the heater hoses as they enter the firewall. The 3/4 hose (thicker of the 2), will be warm/hot. The 5/8 hose (smaller one) will be almost ice cold. Also while holding the 3/4 hose apply as much pressure as you can between finger and thumb. With your other hand rev the engine by turning the throttle coupling and you will feel the hose expand under pressure if the core is plugged. You can try the same thing on the smaller of the 2 hoses. When the engine is reved you might feel the hose trying to collapse.

2. How much does it cost to change a heater core.
Answer: A lot. Probably $600 or more as the recommended procedure calls for the complete removal of you dash and all the electrical components, radio, air conditioning, air bags etc. The dash must come completely out of the vehicle. I know this sounds extreme but I cannot see any other way. Be carefull if you attempt this yourself as airbags can deploy if not properly disconnected?

3. How do I know if it is my thermostats fault?
Answer: Simple answer, It isn't!!! Your heater core is supplied with warm coolant that bypasses your thermostat. This comes directly from your engine block and circultates directly to your water pump even when your thermostat is closed. Even if it were stuck open you would get some heat out. Because of your heater there will always be some coolant cycling through your system even when the thermostat is closed. This coolant will not however pass through your radiator.
No heat is not usually caused by a faulty thermostat.

Also, Blazers with Dexcool do not have a summer or winter thermostat. There is only one kind of temperature range as dexcool only operates properly within this range.

4. Is my heater core leaking?
Answer: Visible signs of coolant inside the SUV. Smell possibly, Most likley is a fog that appears on you window leaving a nasty film when your defroster is on.

5. Why is your coolant down a gallon?
Answer: This could be signs of a leak in the system. How does your exaust look. Does it look funny or white. Do you have the occassional hard time starting the vehicle. This could be a sign of a leaky head gasket. GM installs stop leak at the factory to avoid this, so this is the less likely culprit. Next examine all hoses. Pay particular attention to the hose which connects on the underside of the water pump. This may leak a little and be less obvious. Important: Try squeezing the upper rad hose where it goes into the radiator when the engine is warm and running. There should be 15 pounds of pressure at all times when the engine is running. If the hose squeezes easily there is definately a leak.

There may be a faulty radiator cap. If the cap will not hold pressure, then the dexcool will boil at a lower temperature (actually lower than operating temp). Over a period of time this wll lead to a lot of coolant loss and a plugged heater.

Lastly check the water pump with the engine running and a full rad of coolant. Look under the car with a flashlight and pay attention to the back plate on the water pump. If it is leaking you will likely see drips forming here.

Remember, dexcool is to be added with the engine cool and not running. Releaseing the cap with the engine warm and running will only lead to instantaneous coolant boiling over and loss. Make sure the reservoir is full.

My recomendation is to have your system flushed. This is because you have been driving for some time with low coolant. Read the GM bulletin on the problem as they are not kidding around with sludge buildup. At the very least have the heater power flushed and the sytem flushed. This will cost aprox $100 to $150. If the heater plugs again after this, read my previous post on how to backflush the heater yourself. Only use this procedure if the heater has been recently power flushed as it will not remove a major blockage.

Note: A previous posting to one of you threads recommends reversing the in and out feeds to your heater core. DO NOT DO THIS!!!
This is dumb for the following reasons.
1. Hoses are a different size. If you try to squeeze a 5/8 hose onto a 3/4 fitting you may be successfull but, if the 3/4 pipe weld onto the core is weak you will break it off. Then it will cost $$$ to fix as for sure you will need a new core. These welds are not meant for major jerking around. A heater hose should slide on or off easily with no effort at all.

2. allowing the sludge back into the system will only allow it to circulate until it finds its way into the other side of the heater core. It will, guaranteed, end up there eventually and your efforts will be for nothing.

Lastly, If you have recently had a flush, or a new water pump installed, bits of crap may be still coming loose inside the cooling system. I've had this happen and have had to backflush my heater core using the garden hose method several times. I started having to do this about every 3-4 days. Now things have settled down a bit and the back flush is necessary about every 3 weeks. I believe (this part is gut feeling) that if I flush the entire system again it will only loosen more larger chunks of crap and lead to more heater problems. I am content to do the small flushes until they are no longer necessary. I've noticed the bits of crap getting smaller and less as the flushes go on. I'll probably only have to do 1 or 2 more ... I hope.

Goodluck!!!