I have a 2006 Honda CRV. We just replaced the radiator with a new one as a result of a deer impact. I can't get the thing to run without overheating. Little or no coolant is flowing into the radiator. The temp gauge reads hot but the radiator is barely warm. When I turn the heater on full blast it goes down to normal pretty quick and the air is really hot. I removed the thermostat and checked it in boiling water and it opens. There are no restrictions on the bottom end of the radiator. No indication of coolant issues or corrosion. Only thing I can think of is maybe one of the plastic plugs that came with the radiator was not removed and it is blocking flow or the thermostat is in an air bubble or something. I am also trying to figure out the coolant flow path. I was thinking that is was reverse flow and hot water was going into the bottom of the radiator but by studying in the diagrams in the manual it looks like hot water comes out of the engine and into the top of the radiator as normal but maybe I am wrong. Why would they put the thermostat at the bottom or cool end of the radiator?
2006 CRV can't get coolant to flow through radiator
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It IS a reverse-flow cooling system. Like others have found, it is not easy to purge air pockets out of the system....
The usual trick is to run the engine for ten minutes, then shut it down. That allows the thermostat to heat-soak and open, finally, allowing the coolant to flow.
THEN you can hold the engine at 2000 - 2500 RPM for a minute or two so that the coolant velocity removes most of the air.
Keep checking cold coolant level at the radiator cap for 5 - 10 drive cycles. It will probably continue to purge air that long.
Post back with results!
The usual trick is to run the engine for ten minutes, then shut it down. That allows the thermostat to heat-soak and open, finally, allowing the coolant to flow.
THEN you can hold the engine at 2000 - 2500 RPM for a minute or two so that the coolant velocity removes most of the air.
Keep checking cold coolant level at the radiator cap for 5 - 10 drive cycles. It will probably continue to purge air that long.
Post back with results!
We did all this and it still won't open the thermostat. So water leaves the top of the radiator and comes in through the bottom? Normally hot water goes in the top and out the bottom and I can't see how that would work with the thermostat on the bottom.
Did you install a new thermostat with the new radiator? If so, check the specs on the thermostat. It should begin to open around 170F and be fully open at 194F. If it opens when the water is boiling as you suggested in the original post, it is opening too late.
A thermostat on the bottom is referred to as a cold side thermostat. See:
www.ecoboostperformanceforum.com
A thermostat on the bottom is referred to as a cold side thermostat. See:
Hot side vs Cold side thermostat info
Hot side vs Cold side thermostat info
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running the car does not help at all I been through that experience, you got to BURP the car,, once you get teh air pocket out it will stop the overheat. it is not fun doing so.
A person sees me with a lock in hand, they asked me how to put lock in, I taken all the time in the world to help out, but yet many know how to do a simple youtube search for a simple solution. since nothing is on a 2nd gen about burping, be the first to do so when you get it done
we love helping out we do, but if stumped watch a few vids good luck and hope you resolve it,
A person sees me with a lock in hand, they asked me how to put lock in, I taken all the time in the world to help out, but yet many know how to do a simple youtube search for a simple solution. since nothing is on a 2nd gen about burping, be the first to do so when you get it done
we love helping out we do, but if stumped watch a few vids good luck and hope you resolve it,
@perryg114 you mentioned you hit a deer. Is the radiator fan turning on when the engine gets up to temp?
keep us informed of you fix.
keep us informed of you fix.
No it won't come on because there is so little water flowing into the radiator. I hot wired the fans and the radiator got cold really fast. Since the fans are controlled by a sensor at the bottom of the radiator, they never come on because the radiator is not getting hot enough.
I am going to put a thermocouple in the water when I heat it up to figure out when it opens. It could be that the thermostat is still the problem but the temp guage was just about pegged and it still did not open which you would think the water would be above 212F (boiling water) when the gauge is pegged. I still have not ruled out a plastic plug clogging things up but if that is the case it has dislodged and gone into the system. There is no plug on the bottom end. I was trying to figure out the flow path. Does the water come out of the top of the radiator or does it go in the top of the radiator. If the water comes out of the top then the plug could be in the top junction block area if it comes into the top, the plug could be in the top of the radiator.Did you install a new thermostat with the new radiator? If so, check the specs on the thermostat. It should begin to open around 170F and be fully open at 194F. If it opens when the water is boiling as you suggested in the original post, it is opening too late.
A thermostat on the bottom is referred to as a cold side thermostat. See:
Hot side vs Cold side thermostat info
Hot side vs Cold side thermostat info
@perryg114 If your radiator fan does not come on it sounds like the relay or temp sensor that commands it is damaged. I would concentrate at this area.
You can use an OBD scanner to monitor engine temps.
I can tell you from experience, the reading (which is NOT the dash gauge reading) won't budge even after 30 minutes of idling. The fans will NOT come on even with everything else working as it should. Its just the air bubble.
Letting the t-stat open after a period of heat-soaking does it every time for me...perhaps you could tell by monitoring the bottom hose temp with a non-contact pyrometer.
++++++++++++
In a reverse-flow radiator, the water goes IN on the bottom, and OUT at the top.
I can tell you from experience, the reading (which is NOT the dash gauge reading) won't budge even after 30 minutes of idling. The fans will NOT come on even with everything else working as it should. Its just the air bubble.
Letting the t-stat open after a period of heat-soaking does it every time for me...perhaps you could tell by monitoring the bottom hose temp with a non-contact pyrometer.
++++++++++++
In a reverse-flow radiator, the water goes IN on the bottom, and OUT at the top.
This is what we did. Even with all the air out there was very little flow through the radiator.
Ok, checked thermostat and it is opening at the proper temperature. So there is a temperature number on the ODBII buss? I have not hacked into that one yet. I have a scanguage II maybe that will display the temperature. The engine was running at about 200F according to my IR thermometer thing. Dash gauge was just about pegged. I removed the top hose and no plastic plug appears to be in there blocking anything. Only thing that may have caused issues is that the antifreeze was too strong. It may have never got hot enough to boil. So I guess there is an air bubble in the system that must be in that thermostat housing. There is supposed to be a bypass loop that keeps that thermostat housing full of water even if the thermostat is closed. There is a tiny bleed hole in it that should have eventually let the air out after sitting overnight. I will dilute the antifreeze 50-50 and try again. This is a crappy design. I am not impressed with Honda. This is one we inherited from my folks. Only has about 60k on it. I wish we had left the dented radiator in it now.
There is an ECT sensor in the cylinder head that you can read on a scan tool. ECT to PCM to instrument cluster CPU to temp gauge. The temp gauge does not linearly reflect what the ECT reads, in my personal experience, anywhere from ECT 194-227F on my CRV and the gauge cluster needle doesn’t move at all.
Post #8 from this Acura forum reflects my understanding of the flow of coolant
www.clubrsx.com
My understanding is that on a cold engine the coolant will circulate in the bypass loop until the thermostat begins to open. When the thermostat is partially open, coolant will circulate in the bypass loop and also flow through the radiator. When the thermostat is fully open, it mostly blocks the bypass loop and flow is almost all through the radiator.
I believe some German car manufacturer invented it (BMW? or Mercedes?) and Honda copied it. It has something to do with more even heating of the head and block resulting in better fuel efficiency, less emissions.
Post #8 from this Acura forum reflects my understanding of the flow of coolant
Coolant flow direction
Which direction does coolant flow to the radiator? I'm doing a custom build and need to know where to plumb in bleed lines, so it matters. One theory says the thermostat regulates letting cool water returning from the radiator back into the block, and the other theory is that it lets hot water...
www.clubrsx.com
My understanding is that on a cold engine the coolant will circulate in the bypass loop until the thermostat begins to open. When the thermostat is partially open, coolant will circulate in the bypass loop and also flow through the radiator. When the thermostat is fully open, it mostly blocks the bypass loop and flow is almost all through the radiator.
I believe some German car manufacturer invented it (BMW? or Mercedes?) and Honda copied it. It has something to do with more even heating of the head and block resulting in better fuel efficiency, less emissions.
Are you saying you did not use 50/50 antifreeze to begin with?
I thought there was more water in the system. I was going to measure it once I got it back together. They never make it easy to drain the block. I did flush with water but evidently did not dilute the stuff in the block enough. Usually, the block is mostly water after flushing and I add pure to get close to 50-50. I don't buy 50-50 because you are buying water. I do put in 50-50 when I am sure the block is drained.
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