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Discussion Starter · #1 ·
2003 crv. Great little car we have had since 2006. Last couple years have had poor heat with setting at top. It always used to cook you out. Have flushed and back flushed the heater core and it has good flow. The hot hose is very hot and the return hose is cool with fan running full blast and temp set high. The temp of the air flow gets less as it runs. Have had hoses and valve off and no restrictions. Pulling supply hose off before the valve and running engine and rad full there is very little flow coming out of block. Flushed both directions thru both heater hose connections on engine. No change and like the heater core the flow thru looked fine on the first application of hose flush. This vehicle corroded a hole in the throttle body coolant passages that actually let coolant into the throat of the throttle body and caused symptoms of what I thought at the time was a head gskt leak. Stopped the leak with some really good head gskt leak repair, not bars leak. Finally got car home from Phoenix and discovered where the leak was and replaced the throttle body, car had shown up with surging idle that was caused by coolant getting into the idle air bypass valve and causing it to seize up. The corroded coolant passage thru the throttle body was completely blocked off by the sealer. So i was starting to think that the block seal may have caused the heater core to plug except that the lack of heat was well before the TB problem. Plus i have just flushed everything in sight. The T stat is good as the coolant gets up to temperature fine. Have looked thru all 3 heater hose pieces and the walls are good so nothing collapsing. It is odd how the return hose from core is plumbed into either the water pump or the lower T stat housing. And that the upper coolant housing that the upper rad hose connects to has a 5/8 inch hose plumbed from it to the “water pump backside under the intake manifold. Any ideas. I have been pulling wrenches and running a repair shop for almost 50 years now and am not used to being stumped. I ;understand air can be a problem so am making sure its all bled out and confirm it by feeling the steel coolant line that goes around the PCV air inlet into the cam/valve cover. Haven’t tried specifically the jacked up front to bleed air. Hopefully no one suggests a weak water pump. They either work or they don’t. In 50 years have only ever seen one water pump impeller come loose from the shaft and its symptom was major overheat.
 

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Do '03 Vs have a heater control valve? If the heater core is flowing freely, BOTH hoses should be too hot to touch for very long. The vehicle didn't cause corrosion, poor maintenance did. I've seen water pumps where the impeller fins/vanes were completely corroded away, due to poor maintenance.......no leaks, no noise and no flow either. Any corrosion anywhere that coolant flows indicates poor maintenance. Is the heater core fed with coolant from the head or the block?
 

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Discussion Starter · #3 ·
Do '03 Vs have a heater control valve? If the heater core is flowing freely, BOTH hoses should be too hot to touch for very long. The vehicle didn't cause corrosion, poor maintenance did. I've seen water pumps where the impeller fins/vanes were completely corroded away, due to poor maintenance.......no leaks, no noise and no flow either. Any corrosion anywhere that coolant flows indicates poor maintenance. Is the heater core fed with coolant from the head or the block?
Fed from end of cylinder head opposite side from the upper rad hose housing. Yes the corrosion is due to not frequent enough changes of coolant. I was mistaken, we bought it in 2008. Every couple years i drain out what i can and replace with fresh mix but i guess its not enough.
I did have a go at jacking front end up and running the motor at 2000 rpm while i dribbled in last bits of coolant. And then cracked the top edge of the upper heater core hose and ill be damned if the flow didnt improve after that. Pretty much back to the level of heat output i think i remember. Heater hoses now too hot to hold onto continuously. Before this the outlet hose was very cool and i could hold my hand on it without problems. 160 F hose i used to be able to put my hand on but not leave it there. 180 could just put hand on and off quickly.
Fingers crossed, will run it down the road tomorrow and will be good. Still. Baffles me that it could run with air in the system for several thousand km and bleed itself out.
 

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Coolant flow can be a strange opponent, that's for sure. Those pesky air bubbles can also cause similar problems with plumbing. Some years ago, I had to replace my main kitchen sink faucet. The original had two valves - hot and cold. But they pretty much quit making those long ago, so the new one had a single valve and a large lever-type handle. That thing drove me just about insane when I installed it, as it had an air bubble in it that caused a shudder every time the water was turned on. I tried everything you can think of, for years, nothing ever worked. After about five years or so, I needed to disassemble it and replace the plastic and rubber valve/seal assembly (I hate the crappy modern stuff, much preferred the good old brass internals). While I was at it, I systematically, step-by-step, bled the thing again, as I re-assembled it. Made no difference. The air bubble is still there. Sounds slightly different now, but still there. Aargh!! Not noticeable if you turn it on slowly, but when you just open up wide open, it's annoyingly there. I was visiting a friend recently, who had the same type of faucet, and it has the same issue! Who knew!? I give up.

I've had similar coolant flow issues over the years. Makes me wish for the time when heater hoses attached to pipe fittings with hose clamps, providing a convenient bleeding method when needed. But no more. A collapsed lung/tension pneumo-thorax is easier to deal with, if you believe the tv. But I have worked on cars I wound up wanting to stab.
 

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Fed from end of cylinder head opposite side from the upper rad hose housing. Yes the corrosion is due to not frequent enough changes of coolant. I was mistaken, we bought it in 2008. Every couple years i drain out what i can and replace with fresh mix but i guess its not enough.
I did have a go at jacking front end up and running the motor at 2000 rpm while i dribbled in last bits of coolant. And then cracked the top edge of the upper heater core hose and ill be damned if the flow didnt improve after that. Pretty much back to the level of heat output i think i remember. Heater hoses now too hot to hold onto continuously. Before this the outlet hose was very cool and i could hold my hand on it without problems. 160 F hose i used to be able to put my hand on but not leave it there. 180 could just put hand on and off quickly.
Fingers crossed, will run it down the road tomorrow and will be good. Still. Baffles me that it could run with air in the system for several thousand km and bleed itself out.
Does your '03 V have the cooling system pressure cap on the radiator or on the bottle???? If the pressure cap is on the radiator, frequently remove the radiator cap, COLD motor.....coolant level should always be up in the neck of the radiator. If not, add fresh 50/50 to that level, again COLD motor. If the system is simply "burping air" (no coolant leaks), dropping coolant level will eventually stop and coolant level (cold motor) will remain up in the neck of the rad, presuming all components of the cooling system are healthy.

If the pressure cap is on the bottle or the radiator, keep an eye on cold coolant level in the bottle, BUT also check cold coolant level at the radiator, if the pressure cap is on the radiator. I can't stress enough any/all coolant checks should be done only on a COLD motor.

You already know corrosion has formed in the cooling system/caused issues inside the motor and anywhere else coolant flows.

I would sleep better knowing the water pump was new/functioning 100%.

 

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Discussion Starter · #6 ·
Does your '03 V have the cooling system pressure cap on the radiator or on the bottle???? If the pressure cap is on the radiator, frequently remove the radiator cap, COLD motor.....coolant level should always be up in the neck of the radiator. If not, add fresh 50/50 to that level, again COLD motor. If the system is simply "burping air" (no coolant leaks), dropping coolant level will eventually stop and coolant level (cold motor) will remain up in the neck of the rad.

If the pressure cap is on the bottle or the radiator, keep an eye on cold coolant level in the bottle, BUT also check cold coolant level at the radiator, if the pressure cap is on the radiator. I can't stress enough any/all coolant checks should be done only on a COLD motor.

You already know corrosion has formed in the cooling system/caused issues inside the motor and anywhere else coolant flows.

I would sleep better knowing the water pump was new/functioning 100%.

Yes checking in the rad to confirm your coolant bottle return has always been something i have preached about to many people. This unit has the cap on rad. Opened it up this morning before i took it for a spin and it did have some air in top of rad. Refilled it and the bottle. Damned if it was back to not producing much heat again. Will do a jacked up rebleed again today and see what happens. Thanks for the water pump picture. Wouldn’t believe it if I hadn’t seen the pic. Did it loose the impellers from loose pump bearing? I’d spot i a new water pump if it wasn’t such a pain in the ass to change...but who knows.
Funny story. When apprenticing isn’t eh 70’s the brightest kid in the 1st year class had a question for the class as he had just done a valve grind on a customers car and couldn’t figure out how to get the coolant into the motor. He was filling the coolant recovery jug and the engine would get snapping hot. Suggested he add the coolant in the rad and he explained he couldn’t do that as the cap said “do not remove” on It. Sheesh. Book learned smart but no common sense.
 

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Approx how much coolant did you need to add?........if only a small amount, I don’t think air is your problem.......but keep checking daily, COLD motor. It shouldn’t take more than 3-4 full hot/cold cycles for coolant level to remain steady up in the neck of the rad. If you have to keep adding coolant after that, you have an air or coolant leak or both.

Were both heater hoses hot? The other half of poor heater performance is the trap door under the dash that allows more/less outside or cabin air to pass thru the heater core.

One other note.......it is impossible to re-fill a cooling system (from empty) too slowly. The slower coolant is added, less air to “burp”.
 

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How does that funnel get the air out? What happens when you remove the half full funnel/cap?.......excess coolant go everywhere, or is there a check valve? There’s no way those tiny air bubbles in those videos would cause poor flow thru a heater core.

My opinion is, using a funnel like that is a really good way to fill the cooling system TOO FAST, thus trapping more air. I’m talking about re-filling the cooling system by a quart, or less, at a time. Yes it is slow, but less air will be trapped. 4 banger cooling systems don’t hold much coolant.

When coolant level reaches just below the neck of the rad (no funnel), or appears in the pressurized bottle, stop adding coolant. Start the motor, let it idle, put the heater on max IF there is a heater control valve. No heater control valve, no need to set heater to max. Watch the coolant level while the motor idles, burps and comes up to operating temp. Keep the coolant level visible in either the radiator or pressurized bottle. It’s pretty simple and you don’t need a $30 funnel with all sorts of plastic pieces.

Please note that I am saying pressurized bottle.......you can not fill the cooling system thru a non-pressurized bottle. If your system has a non-pressurized bottle, the cooling system is re-filled at the radiator cap on the radiator........even though the radiator cap may say “Do Not Remove”.?
 

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How does that funnel get the air out? What happens when you remove the half full funnel/cap?.......excess coolant go everywhere, or is there a check valve? There’s no way those tiny air bubbles in those videos would cause poor flow thru a heater core.

My opinion is, using a funnel like that is a really good way to fill the cooling system TOO FAST, thus trapping more air. I’m talking about re-filling the cooling system by a quart, or less, at a time. Yes it is slow, but less air will be trapped. 4 banger cooling systems don’t hold much coolant.

When coolant level reaches just below the neck of the rad (no funnel), or appears in the pressurized bottle, stop adding coolant. Start the motor, let it idle, put the heater on max IF there is a heater control valve. No heater control valve, no need to set heater to max. Watch the coolant level while the motor idles, burps and comes up to operating temp. Keep the coolant level visible in either the radiator or pressurized bottle. It’s pretty simple and you don’t need a $30 funnel with all sorts of plastic pieces.

Please note that I am saying pressurized bottle.......you can not fill the cooling system thru a non-pressurized bottle. If your system has a non-pressurized bottle, the cooling system is re-filled at the radiator cap on the radiator........even though the radiator cap may say “Do Not Remove”.?
during the thermostat opening and closing while performing a cooling system bleed the level goes up and down so that funnel keeps coolant in the radiator and or pressure tank if its that design with out making a mess so after replacing a cooling system part or opening the system, with the engine still off hook up this funnel and the proper adapter and fill it up until it stops taking anymore coolant then turn on the heat and start the engine and stick a gas pedal depresser, snow brush whatever works on the gas to hold the rpm at 2500 and let it run for about 5 minutes keeping the funnel 1/2 full then shut the engine off for 2 minutes then start it if it still has no heat repeat the 5 and 2 until it has heat ,the main thing is if it don't have heat its not flowing yet that means it has air trapped and by doing the heat soak it will eventually open the thermostat if you keep running with no flow no heat it will boil and make a mess shooting geyser coming up out of the funnel so anyway then after you see no more air bubbles shut the engine off squeeze the upper hose to raise the level in the funnel then stick the plastic stick down in the funnel and lift the funnel, the stick plugs it from leaking, then put that in the overflow tank or another container and remove the adapter and put the radiator cap on it works every time no mess no boiling coolant causing more air pockets or possible inadvertent engine damage ,note if it already has heat the heat soak method is usually not needed if the temperature stays under 200F some cars like Volkswagen have a very delicate plastic impeller and will melt, but its not necessary on some designs these Hondas usually do need the heat soak method , the funnel just simplifies the job I know its not a must and cost effective if you are only using it once or twice,at harbor freight they are 1/2 that price
 

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he explained he couldn’t do that as the cap said “do not remove” on It.
Reminds me of an Aggie joke. News report: "This just in - When a passing motorist on Hwy. 6 became concerned and notified police, they found a returning student, dead in his car. He had apparently been sitting there, parked on the shoulder, for several days, in front of a sign that said DO NOT PASS."

The competition for Darwin Awards is much stiffer these days.
 

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How does coolant level go up and down. How do you run the motor at 2500 rpm for 5 minutes and have no heat? How can coolant not be flowing yet?.........the instant the motor starts, the water pump is spinning, thus pushing coolant instantly in a loop thru the block, then to/thru the head (and heater core), over, over and over again, block/head, block/head, etc. Why do you need to keep stopping/starting the motor?......doing so just slows down the burping process. Horizontal flow rads burp a little slower than vertical flow rads. The radiator is not added into the flow loop until the tstat begins to open.

How do have a post as long as #10 and no punctuation?
 

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Discussion Starter · #13 ·
Reminds me of an Aggie joke. News report: "This just in - When a passing motorist on Hwy. 6 became concerned and notified police, they found a returning student, dead in his car. He had apparently been sitting there, parked on the shoulder, for several days, in front of a sign that said DO NOT PASS."

The competition for Darwin Awards is much stiffer these days.
That’s a great idea. Just ordered one. Thanks.
How does that funnel get the air out? What happens when you remove the half full funnel/cap?.......excess coolant go everywhere, or is there a check valve? There’s no way those tiny air bubbles in those videos would cause poor flow thru a heater core.

My opinion is, using a funnel like that is a really good way to fill the cooling system TOO FAST, thus trapping more air. I’m talking about re-filling the cooling system by a quart, or less, at a time. Yes it is slow, but less air will be trapped. 4 banger cooling systems don’t hold much coolant.

When coolant level reaches just below the neck of the rad (no funnel), or appears in the pressurized bottle, stop adding coolant. Start the motor, let it idle, put the heater on max IF there is a heater control valve. No heater control valve, no need to set heater to max. Watch the coolant level while the motor idles, burps and comes up to operating temp. Keep the coolant level visible in either the radiator or pressurized bottle. It’s pretty simple and you don’t need a $30 funnel with all sorts of plastic pieces.

Please note that I am saying pressurized bottle.......you can not fill the cooling system thru a non-pressurized bottle. If your system has a non-pressurized bottle, the cooling system is re-filled at the radiator cap on the radiator........even though the radiator cap may say “Do Not Remove”.?
im thinking this is to be used with the front end jacked up. More diligent bleeding has helped as i now have heat. Woohoo.
 

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I'm reasonability sure the top of radiator OR the pressurized bottle are the highest points in the cooling system. Trapped air will always migrate to the highest point as coolant/air flow throughout the cooling system. The air will be held at the highest point as coolant continues to flow/circulate round and round thru a healthy cooling system.

Checking coolant level every day for a week, COLD motor, after a cooling system drain/refill is very important as it is virtually impossible to illuminate all air by lifting the front of the vehicle or using a funnel. It takes repeated heat/cool cycles over time to eliminate all air from the system. Filling the cooling system and slamming the hood closed for a month or two is a good way have a partially filled cooling system.

Both pressurized bottles and non-pressurized bottles will always have/hold air. The bottle, is where the air that has been removed from the coolant, is trapped/held. The top of the radiator should never have air in it, once the system has completely burped after repeated heat/cool cycles.
 

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How does coolant level go up and down. How do you run the motor at 2500 rpm for 5 minutes and have no heat? How can coolant not be flowing yet?.........the instant the motor starts, the water pump is spinning, thus pushing coolant instantly in a loop thru the block, then to/thru the head (and heater core), over, over and over again, block/head, block/head, etc. Why do you need to keep stopping/starting the motor?......doing so just slows down the burping process. Horizontal flow rads burp a little slower than vertical flow rads. The radiator is not added into the flow loop until the tstat begins to open.

How do have a post as long as #10 and no punctuation?
just telling how it's done in the real world,thats how you get all the air out ,on customers cars I cant keep adding coolant a couple of days later works every time on hundreds of [email protected]
 

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I'm speaking from 55 years of real world experience regarding draining/flushing/re-filling cooling various cooling systems.

Coolant level will drop as air is removed. It does not go both up and down while the system is being re-filled. To each his own on the funnel. I've never re-filled a cooling system from a gallon jug.....quart, or less, at a time (motor off) until coolant appears in the bottle or the neck of the rad. Start the motor, let it idle, turn the heater on IF the system has a heater control valve and continue to add coolant as the level drops in the rad or pressurized bottle. Check coolant level in the bottle and/or radiator (COLD motor) for several heat/cool cycles......until the coolant level remains steady when the motor is cold.

My way, my results, my opinion, no funnel and has never failed me yet, including this past spring doing a drain/re-fill on our '09 RAV4. YRMV.
 

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Good video.......that part about checking coolant level for a week or two after re-filling was good advice as well.

Since it was not in the video (maybe I missed it), when re-starting the motor, make sure the a/c is OFF as a/c ON runs the radiator efans. Also, when turning the heater ON, set temp to MAX and blower speed to MIN (motor will heat up faster). Again, my thinking is, you can not re-fill coolant too slowly, A very slow re-fill minimizes air in the system, especially if you are re-filling the cooling system thru a pressurized recovery bottle.
 
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