HEATER CORE KEEPS PLUGGING UP

I flushed my coolant system last month and it keeps plugging up my heater core. What is the correct way of doing an entire engine flush. Do I use distilled water only? How do I get all the antifreeze out of the head?

Use a cooling system flushing additive to clean out the cooling system. Follow the product label directions, and follow up with a fresh water flush. Antifreeze concentrate should be mixed 50/50 with distilled water.

Just fill with tap water, bring it to operating temperature, drain from the radiator and block, repeat as needed. Once its running clean, fill it with 50/50 green and distilled water, let it run for a few weeks and recycle if needed. It took me around 6 cycles to get all the crud out.

What does your coolant look like? In some cases the radiator and/or heater core act like sponges and its not practical to try and flush them. As an example, one of my XJ's appears to have had Dexcool mixed with Conventional Green at some point. When I removed the thermostat and water pump, the head and block looked OK. When I first started flushing, it would turn brown just idling after a refill. After using flushing additive, and enough drains and refills, it would turn brown after 200 miles. Continuing to drain and refill I got much longer before the coolant would change. I probably did this 15 times. I still had a ring of crap under the cap and it would get into the coolant jug. Eventually the radiator failed and was replaced and I haven't had a problem since. I would have been cheaper and a helluva lot quicker to replace the radiator in the first place.

Try back flushing the heater core.



In the future, if you are flushing the cooling system, take some heater hose and make a loop from the water pump to the thermostat housing. This will help keep crap out of the heater core, if its not already clogged.

This is why i take mine into a rad shop every 5 years.I don't have a problem with it. Worth the 100 bucks to me for peace of mind.

Its a good idea to put a garden hose on the inlets and outlets, blows a lot of junk out

ehall said:

Its a good idea to put a garden hose on the inlets and outlets, blows a lot of junk out

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Just be careful of the pressure, anything over 25-30 PSI and you may damage stuff and/or pop seems. Garden hose pressure can be anywhere from around 60-150 PSI.

I've checked radiators with a pressure kit (stoppers) and air pressure before, you just soap them down and look for bubbles, like checking for a tire leak. You can see the radiator swell noticeably at a round 25 PSI, which can't be good for the seams and or seals on a radiator or a heater core.

I disconnected the heater hoses near the heater valve, blew out the coolant with fresh water, blew most of the water out with low pressure air, raised the hoses above the core and tied them up, filled with Vinegar and let it sit overnight. Flushed with fresh water the next day. Blew it out with air again, you will get much, but not all the water out. Heater worked like new. I also soaked the heater valve in vinegar overnight, the insides were pretty plugged up. I eventually had to swap in a new heater valve, my old one was leaking and really brittle from age.

What anti-freeze are you using? Many of the aftermarket anti-freezes on the store shelves are OAT, even a DexCool derivative, they are NOT to be used even if they say They work in every brand/model, mixes with any color anti-freeze. Its a totally bogus claim, and they have lost in court over it, but the court had no power in stopping them, it was just trademark court.

Use the original Green, IAT anti-freeze. If you can't find it, then HOAT should work OK, Zerex G-05 is the Chrysler HOAT. Do NOT use any OAT anti-freezes, and many of these bogus aftermarket anti-freezes are OAT but do NOT say it, they very vaguely allude to being some sort of universal anti-freeze and they are NOT.

If you don't know what has been in the cooling system, flush it thoroughly, make sure all the old coolant is out of it.

Mixing OAT, especially DexCool or its derivative, with IAT (original Green) will cause solids to form. The original Green, if you leave it in the cooling system too long (Its suppose to be changed every 2 years), or you mix it with hard water (tap water from areas with lots of minerals dissolved in the water) it will form solids as well. To many people neglected the original green anti-freeze (which is arguably still the best protecting anti-freeze) and the resulting problems is why we have 2 dozen different long life anti-freeze that have all sorts of different compatibility problems that no one can keep track of.