Question on flushing heater core

HOW DO I DO IT? where do i find the hoses?? How do i disconnect them... blah blah..

i hate NO HEAT and its -8 now with a -40 windchill in CT!!!

I also got a new thermostat i need to install!!!! brrr
help!

its running @ like 125degrees MAX!!!

Sounds like a thermostat to me...its easy - its at the front of the intake manifold......follow the upper radiator hose to a flange with 2 bolts on it....try that first before you flush the core....if you need anything else just pm or post up....I'm in CT too so I know how cold it is !

I agree with Alex...replace the thermo and continue...my 4.3 w series...runs at about 210 on the gauge after going up to 250 or so b4 the thermostat opens...and I just replace the heater core so it heats great...I wish you well and have a good weekend... :o)

its running @ like 125degrees MAX!!!
yeah, i know how to change the thermostat, i just nned a 13mm metric long socket and the only day it was warm enuf to change i only had reg sockets, not mm's... hopefully tomorrow!

Thanks!! you have a good weekend too

I agree with the others, try the thermostat first, as the others said, follow the top hose to the t-stat housing. Be careful getting the bolts out of that aluminum intake though, you might have to use a little care to ease them out. and make sure you clean the gasket area well.
As for the core flush, you might try a chemical flush first...drain cooling system, follow directions on flush kit(you can get these kits at most parts stores).. drain again and refill with fresh 50/50 mix of antifreeze and water. If your truck is newer they use DEX-Cool antifreeze.
My blazer also runs in the 210-250 or so range..so the t-stat might be your only need.

I agree with the thermostat replacement, definately sounds like he problem. If you end up wanting to flush the heater core, all you have to do is disconnect the heater hoses at the firewall, take a hose with a nozzle, stick it in, wrap a wrag to seal it a little, spray water, watch it come out the other side. Do that a few times on each side. Blow it out with air in between switching sides. Put heater hoses back on, top back off with coolant. I have too flush alot of heater cores at the shop I work at in MI, its really easy but messy. HTH

Flush the heater core by its self, disconnect the hoses from the engine to do so. Then flush the whole cooling system and refill with new Prestone dexcool. The core in my caprice was clogged solid. It's a common on these vehicles, check out other posts there's alot. It even happened to my caprice. Dexcool doesn't last as long as they say.

thanks so much you guys! ive had the thermostat for about 2 weeks but it hasnt topped 10 degrees yet outside!!!

unfortunatley i go back to college wednesday -- at least i fixed my 4x4 before the 6" of snow coming tonight!!!

BY THE WAY :: when i bought my blazer in november it was COMPLETLEY OUT OF ANTI-FREEZE!!! idiot never checked it before me!!!

Im pampering her now, so hopefully she'll shape up!!

Thanks again, appreciated!

Does someone have instructions on how to flush the system. Oh and not the GM instructions. I'm looking for something in plain english.

I can sympathize with the heater core problem as I have just gone through 3 weeks of hell rectifying the same problem. I offer these words of wisdom and some advice:

1. Never let your coolant reservoir go dry. This will lead to a clogged heater real fast. GM has a bulletin ... 99-06-02-012D which explains the flushing procedure. It wordy but actually resonably easy to understand. Most rad shops are not aware of the bulletin. The dealer will be aware.

2. If you go for the general cooling system flush it will likely last no more than about 2-3 weeks. Mine last exactly 2 weeks. GM recommends an acid flush. It takes about 6 Hrs to performand costs about $300.

Water pumps do not like acid flushes as the neutralizer can destroy synthetic seals in the lower portion of the water pump. Mine lasted 2 days after the acid flush before it went ... back to the shop.

I must admit that the system looked real clean after the flush. The inside of the rad was a shiney metalic look after the procedure. Heat was unbearable to touch ... hot. Success or so I thought ...

3. Heater got plugged exactly one week after the acid flush so I got aggressive and took matters into my own hands. I purchased 1 5/8 heater hose and 1 3/4 heater hose. I purchased 2 brass female garden hose couplings, and 2 brass quick connects to one end of each heater hose. I also puchased an inline on/off shuttle so I can turn the water in the garden hose on or off at the hose end.

Disconnected the 2 heater hoses from the firewall of my blazer and attached the new heater hoses using the existing spring clamps. Armed with a 5 gallon pail and a garden hose from my house attached to a hot water tap, (Its -20 outside), and the on/off shuttle and quick connect assembly on the other end (car side). I connected the hose to the quick-connect of the 5/8 heater hose. The 3/4 heater hose dangles over the fender and into the plastic 5 gallon bucket. Turn on the hot water slowly using the on/off shuttle. This should back wash the heater core only.

Watch some sludge plop out followed by some dexcool and clear water. Stop here and dispose of the antifreeze responsibly. Alternating the garden hose between the 2 heater hose quick connects can forward and backward flush your heater core. (aprox 10 min job)

Once done, remove the hoses and reconnect the original heater hoses. Top up with dexcool and you are set to go. This procedure worked for me as my system had been flushed extensivly twice within 3 weeks. Any plugging would have been minimal and did not require a power core flush. I plan on doing this proccedure every few weeks until I notice no sludge buildup. It only takes 20 minutes once you have the quick connects installed on the extra hoses.

4. Some Blazer owners have flushed and converted to green antifreeze which does not have the same sludge problems. Problem with this is if there is scalling or deposits left in the bottom of the engine block after a flush, they will find there way back to the heater eventually whether the coolant is green or orange. This is the reason I stayed orange.

5. Even with orange coolant flush the system at least every 2 years.

Sorry for the long winded explanation, but I felt you might want options.

I noticed that you have asked other questions relating to this subject on another thread. I will post a reply here as it relates to this thread as well.

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: Your heater core is supplied with warm coolant that bypasses your thermostat. This comes directly from 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.

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.

Goodluck!!!