Heater Core Flush (1 Viewer)

[krash]

I know there are multiple posts in regards to reverse flushing it but I can't seem to find the answer I'm looking for. My question is - Where would I hook the water hose up to reverse flush?
I'm assuming the hoses I would use are the two hoses that go into the top of the firewall after the heater T's? If that is correct , then looking down on them from the top of the engine which one is the input and which one is the output flow from the heater core?

 

[flintknapper]

For best results...flush both directions starting with a back flush.

The heater tube nearest the drivers side is the inlet, the other is the return.

 

[2001LC]

To add to that^: Upper hoses are front heater core, lowers rear heater.

I personally would never hook up a garden hose to coolant system unless absolutely necessary. Tap water introduces minerals to the coolant system, we don't want that. I use distilled water only.

I manually flush heater cores with a pump, only when concerned a foreign object may have entered it. I don't like disturbing the hose connections unless necessary. If the two plastic heater Tees have not been replaced, I do those at time of flush along with thermostat.

 

[krash]

To add to that^: Upper hoses are front heater core, lowers rear heater.

I personally would never hook up a garden hose to coolant system unless absolutely necessary. Tap water introduces minerals to the coolant system, we don't want that. I use distilled water only.

I manually flush heater cores with a pump, only when concerned a foreign object may have entered it. I don't like disturbing the hose connections unless necessary. If the two plastic heater Tees have not been replaced, I do those at time of flush along with thermostat.

So we have two heart cores in these? My problem is this - when I turn the front heater on it blows cold air when I have it set to hot temp and full blower. when the temp is set to hot and I turn the blower off I can feel hot air seeping through the vents (if that makes sense) and when I turn the blower to full again it slowly gets cold (maybe 10 seconds) - this is with any vent setting (defrost, floor, top vents etc..) the rear heater blows hot air like normal out of the two vents on the back of the center console. any ideas?

 

[nissanh]

With digital climate control, if the outside is hotter than the setting, I think the heater never turns on. I have a clogged heater. Rear blows hot withn in 3 to 4 minutes and front takes time to blow hot air. I flushed it twice and got some residue out. I am planning to use vineger (5% acetic acid) to dissolve CaCO3 build up. Will leave it there for 2 to 3 days to get all carbonates to dissolve.

 

[2001LC]

So we have two heart cores in these? My problem is this - when I turn the front heater on it blows cold air when I have it set to hot temp and full blower. when the temp is set to hot and I turn the blower off I can feel hot air seeping through the vents (if that makes sense) and when I turn the blower to full again it slowly gets cold (maybe 10 seconds) - this is with any vent setting (defrost, floor, top vents etc..) the rear heater blows hot air like normal out of the two vents on the back of the center console. any ideas?

Edited: Sorry I miss read that. I now see "rear heat blow hot" But still I'd go through this procedure.

Very likely your coolant level is low, and needs topping and burping. Try this in the morning after your engine has cool down for 6 to 8 hours. Remove radiator cap. Top radiator with Toyota coolant. 98-02 use Toyota LL (red), 03-07 use Toyota SLL (pink) (Toyota SLL use may have begun later than 03, check your owners manual). If you don't have coolant use distilled water (never tap water). Once radiator is topped, fill your reservoir about half way between marks. Do this each morning until radiator will not take any more, and reservoir hold it's level.

If radiator is full it is possible to have and air bubble in heater coolant lines. Try this: With full radiator and both heaters on max heat, drive around and stomp on brakes. Sometime just this alone will free air bubble. I'll hear a gurgle sound as bubble frees and coolant flows. Then go back to burping the next morning.

Again must cool down for 6 to 8 hours before checking and topping radiator.

 

[krash]

Edited: Sorry I miss read that. I now see "rear heat blow hot" But still I'd go through this procedure.

Very likely your coolant level is low, and needs topping and burping. Try this in the morning after your engine has cool down for 6 to 8 hours. Remove radiator cap. Top radiator with Toyota coolant. 98-02 use Toyota LL (red), 03-07 use Toyota SLL (pink) (Toyota SLL use may have begun later than 03, check your owners manual). If you don't have coolant use distilled water (never tap water). Once radiator is topped, fill your reservoir about half way between marks. Do this each morning until radiator will not take any more, and reservoir hold it's level.

If radiator is full it is possible to have and air bubble in heater coolant lines. Try this: With full radiator and both heaters on max heat, drive around and stomp on brakes. Sometime just this alone will free air bubble. I'll hear a gurgle sound as bubble frees and coolant flows. Then go back to burping the next morning.

Again must cool down for 6 to 8 hours before checking and topping radiator.

Ok, I did the burping procedure twice about a day apart at around 30 minutes each time- the first time I saw bubbles coming out and the second I didn't see anything. Over the course of the last week I've been checking the fluid under the radiator cap and it's been full each time. I have been filling the reservoir up (between low and full marks) each time I come out to look every couple days it's always back down to the low mark if not lower. I assumed it was a leak even though I don't see any liquid on the ground. So far I've went through about a 1/2 gallon maybe a little more of the red coolant.
I'll try the slam the brakes method later today.

 

[krash]

With digital climate control, if the outside is hotter than the setting, I think the heater never turns on. I have a clogged heater. Rear blows hot withn in 3 to 4 minutes and front takes time to blow hot air. I flushed it twice and got some residue out. I am planning to use vineger (5% acetic acid) to dissolve CaCO3 build up. Will leave it there for 2 to 3 days to get all carbonates to dissolve.

I'm in Va so we haven't had any really cold days yet but I leave around 3am for work and that's when I've been trying it so it's probably 70 degrees or so lately? still no go unfortunately. I didn't know that about the digital climate control, appreciate the info

 

[2001LC]

The cabin heat will come on no matter what OAT is. If OAT higher or lower than cabin temp, it will change recirculating or fresh outside air setting automatically once fan turned on. Turning on fan powers up the HVAC system.

Make sure both front and rear heaters are set to full HOT and turn fan on HIGH for at least minute, as you drive or run engine for 10 minutes or longer once at operating temp. Again, turning on the fan powers up the HVAC systems, which will then accepts and adjust to the setting you have set. You can turn fan back off, but keep heat setting on HIGH front and rear (make sure rear heat control set to hot). You've not said what year or if a NAV or no NAV system. But I do treat both the same in that I turn fan on, to accept settings like temperature or fresh air.

Heater core failure or plug is not common in a series 100 that is properly maintain. If tap water is ever added it, this will increase likelihood of a plug or failure of cores. There're many types of coolant today, adding the wrong coolant can create a plug or jell the coolant.

You mentioned burping "around 30 minutes each time" not sure what you mean. If you mean; Just top and drive for 30 minutes, then check again next morning (8 hour cool down) that's good. The system is actually self brupping and draws coolant from reservoir as engine cools down. All we are really doing is making sure it's topped with coolant so system can do it's job. It expels coolant into reservoir as coolant expands (heats). If reservoir runs dry it may suck air into top of radiator during cool down. If air in top of radiator, then this cycling in and out of reservoir may not function properly, depending on how much air. This is why we check radiator level first. If radiator cap bad, this moving in and out of reservoir doesn't work as designed either. Old cap should be replaced. You can test a cap, but good luck finding anyone with a cap tester.

Keep burping each morning. Once your radiator is found to the top of the neck/cap in the morning (after a cool down), it usually only takes one more mornings of adding to reservoir before level holds from then on. I've only had and air bubble get stuck in a heater core once. It was after I blew out heater coolant lines with air. This once, I serendipitously stomped on the brakes WITH ENGINE AT OPERATING TEMP and air bubble released. Front Cabin heat begaim working a minute later. I did then need to start burping/topping procedure all over again.

Coolant is very sensitive to temperature. So on a cold morning with OAT of say 40F, the level in reservoir will be lower than when OAT is "say" 80 F. Even 10F will make a noticeable difference in reservoir level. For this reason I set reservoir at low line when OAT is -10 or -20 F (Whatever expected annual low for your area). But if OAT is 80 or 90F, I'll set level at halfway or even higher. When engine is at operating temp, I like to see reservoir at high mark and feel upper radiator hose hot and full/hard.

Minor coolant leaks will not always show on garage floor. Most leaks are just when engine hot and running. But if using Toyota red it will leave a pinkish dry flake (when dry) trail behind from leak.

A weak thermostat opening to much or too soon, engine will run cool and so will cabin heat. But if front cabin heat cool and rear very hot something wrong. Our cabin heat blows very hot, especially the front.

You never said why you wanted to backflush in first place. Was something not working or was this just a 2yr or 30K PM coolant flush?

Did you have heater tees hoses off and possible reconnect hoses wrong. (not easy to do, but possible? Picture are helpful)

Once coolant level set, level only varies depending on temperature. So continually adding indicates a leak. We can talk more about leaks and how to find if your sure you have one.

 

[krash]

It's a 1999 land cruiser with front/back AC and heat

You mentioned burping "around 30 minutes each time" not sure what you mean.

I read on this forum that to burp the system you take the cap off the radiator and turn the vehicle on, let it warm and air bubbles will eventually come to he top of the radiator spout if they are in the system.

Once your radiator is found to the top of the neck/cap in the morning (after a cool down)

This happens every morning I check it - the reservoir is always low though.

You never said why you wanted to backflush in first place. Was something not working or was this just a 2yr or 30K PM coolant flush?

I bought this vehicle about 3 months ago and I just noticed the heater didn't blow hot air in the front so I started researching on this site. It seemed to be one of the easiest items besides the "burping" I described above.

Did you have heater tees hoses off and possible reconnect hoses wrong. (not easy to do, but possible? Picture are helpful)

I have yet to do this I saw the "burping" and figured I'd try that first.
I'm not 100% sure what has been done to it except for what is on CARFAX. Last Carfax line item that performed maintenance.

12/19/2017 @192,645
Antifreeze/coolant flushed/changed
Antifreeze/coolant checked
heater hoses(s) replaced
radiator hose clamp replaced
power steering hose(s)/line(s) replaced
Power steering fluid flushed/changed

It now has a 194k miles on it

 

[2001LC]

Leaving cap off 30 minutes while engine running, I supposed may be helpful. May get in a little more coolant than just squeezing radiator hose to force fluid as FSM recommends. But either way I always finds needs more added after cool down. Often it takes me three cool down cycles.

"Most" any work done at Toyota, history is online. You can also drill down in parts list at toyota.com/owners. Unfortunately not all work is available, sometimes even when done at Toyota. But between carfax and Toyota we often get a really good picture.

Either shop found leaks or PO had hoses replaced as a PM. The clamp was very likely a leak issue. Leaks are important to know about. Reason being. If to low for too long overheating may have been issue. Overheating may blow head gaskets and or wraps heads sometimes. This can lead to coolant leaks along heads gasket. These may or may not be internal (into cylinders).

If sure you're losing coolant, the hunt begins. I start with engine cover and undershield off. Look at front and rear water bypass joints were they bolt to heads (all points), and water bypass pipes & hoses (in front of timing belt cover). Look at all side of radiator, most common if front seam at top where plastic top mates to aluminium cooling fins body.

Next inspect head gasket. All the way around including under intake manifold in valley. Mirrors are helpfuls as is a borescopes.

How does oil look? Not like milk shake I hope.

Youtube has many ways illustrated to check if combustion gasses in coolant system.

What is your skill level i.e: experienced mechanic, shadetree mechanic, DIYer, take to shop most time or something in between?

 

[krash]

"Most" any work done at Toyota, history is online. You can also drill down in parts list at toyota.com/owners. Unfortunately not all work is available, sometimes even when done at Toyota. But between carfax and Toyota we often get a really good picture.

I had no idea about this site - created an account and logged in - looks like in 2015
01/03/2015
AC HEAT DIAG
AC HEAT DIAG ~|~C/S: HEAT DOES
NOT WORK SLOWLY COMES OUT ~|~
~|~REPLACED THERMOSTAT AND GASKET

f sure you're losing coolant, the hunt begins. I start with engine cover and undershield off. Look at front and rear water bypass joints were they bolt to heads (all points), and water bypass pipes & hoses (in front of timing belt cover). Look at all side of radiator, most common if front seam at top where plastic top mates to aluminium cooling fins body.
Next inspect head gasket. All the way around including under intake manifold in valley.

​

I'll start finding out what these things are and start looking.

Oil looked fine and as for my skill level - Up until about a week ago I had no idea what a heater core was or that one even existed. I sold my 2017 TRD Offroad and bought this truck for $7k thinking I would use it to learn and get the satisfaction of fixing it myself. It's been interesting so far.

I really appreciate your experience and help - thank you

Steven

 

[2001LC]

Ok, well I realized now I didn't even mention looking for coolant in PS (passenger side) footwell (heater core is above foot well). Coolant has a sweet smell that if leaking from front heater core, I'd think you'd smell it. Even a leak in engine compartment can be smelt from cabin while driving.

Can you post a picture of your coolant temperature gauge after engine warmed up. They don't move much with temp change, but if running cool or hot we may see that on gauge. Hooking up to the tech stream of you vehicle, you could see actual temperature. But if you don't have a scan gauge, Mini VCI, bluetooth OBD-II, ect. to connect, you can use IR temperature gun and shoot beam onto housing of thermostat. You'll want to see a temperature around 185 f. This tells us if your thermostat is at least holding a proper temp.
Rear heater blowing very hot, is good indication your reaching operating temp. But is it very hot?

If you've top coolant at radiator and reservoir 5 time after a full cool down (8 hours) and still it keeps needing more coolant, you've likely a leak. But there is situation where air doesn't properly bleed out (burp) and you may just be getting a little more air out each time.

1. The most common is a thermostat installed wrong. Thermostat has a jiggle valve, which must be oriented up (at top). Very easy to pull and take a look.
2. Air bubble in heater core is one we've cover.
3. Something plugging heater core or a line could also trap air or just not allow coolant flow. Back flushing can be revealing!

These may help:
Be very careful removing hoses not to move metal piping. The one coming from rear water (V this one) bypass joint often will leak if moved

 

[ikellymo]

For anyone wanting a visual - red is inlet to heater core, and blue is outlet, as measured with IR gun.

 

[Jack90210]

Old thread here but I wanted to add a data point for future reference.

My '07 LX470 cooling system had been reasonably well-maintained (coolant changed maybe every 5 years) and I had recently done a coolant drain/fill when my original radiator split its top at 191K miles.

In the process of replacing it I also drained the block and replaced nearly every hose with new OEM. Since the system was fully drained and open it was a good time to flush the two heater cores; I set up a pump sprayer and connected tubing to an old heater hose to facilitate a low-pressure flush with distilled water.

Result: nothing to report. My cores were totally clean. I was concerned that there might be a few small bits of old crumbled heater tee, but there was nothing. No satisfying black goo and no particulate.

I'm glad that I did the flush, but it wasn't necessary for anything except peace of mind. If I had neglected the system, I may very well have had different results.

PS: Going forward I'll be doing a radiator drain/fill every two years.