Thought radiator cap was cause of original problem which was idle fluctuates between 1000-1500 or 1500-2000rpm. Cap was melted, replaced radiator, flush air out of system, still idled weird, realized thermostat was stuck shut, replaced therm., ran good for a few months, but has started idling weird again... What???
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1. The radiator cap if working correctly it will release pressure in the system provided the cap you have is the correct pressure setting. If you are having a problem with pressure then replace the cap with a new radiator cap with the correct pressure setting. Do not use a cap with a pressure setting other than the original equipment pressure spec. So you do not go to the parts store and buy any radiator cap on the shelf that fits because they come with different pressure ratings and some of these will be totally unsuitable for your car.
2. If the pressure valve is stuck in the "old" cap the pressure release system will not work.
Air pockets in the cooling system can definitely cause overheating and can retard coolant flow through the system. If you are draining the radiator to replace the coolant or replacing the radiator you need to follow the correct procedures for bleeding air out of the system for that particular engine after coolant refilling. Some engines have bleeder screws on the cooling system to assist in the air bleeding procedure and some don't.
There are various causes for overheating so don't assume it will necessarily be solved by bleeding any remaining air from the cooling system and replacing the radiator cap with one that works.
Other causes can be...........
1. Faulty cooling system thermostat. (Replace the Thermostat)
2. Faulty water pump, especially if the impellers have corroded away or have disintegrated in the case of those design genius water pumps with plastic impellers. (Replace the water pump)
3. Cooling fans not working and if so the cause needs to be tracked. Check that your fans are kicking in. If the engine is overheating the fans should be running because they will switch on when the coolant reaches a specific temp and well before the coolant gets excessively hot.
4. A partial blockage in the coolant passages inside the engine but not in the radiator if you have a new one. If the coolant is not changed at the required intervals(frequently the case with many owners) or is over diluted with water you can get a build up of debris. If products like stop leak have been used in the system this can create similar problems with partial blockages inside the engine coolant passages.
5. A compression leak into the cooling system.
If you have bled air from the system and have continuous air bubbles in the cooling system I would suspect a compression leak. In that event a basic leak down test will show if you have compression gasses leaking into the cooling system and from which cylinder(s). The spark plug is removed and compressed air is forced into the cylinder via the spark plug fitting and air bubbles will show up in the coolant of there is a leak into the cooling system.
Have the problem with overheating addressed immediately. Running the engine with an overheat condition will cause expensive engine damage many times the cost of fixing the overheating issue.
Several possible causes:
Not enough coolant.
Worn out vanes on the water pump
bad sensor (is it actually too hot?)
Cooling fan not coming on.
cooling fan shroud broken.
Radiator covered or plugged.
radiator cap not holding pressure
leak in cooling system (water pump shaft seal is a common culprit and hard to spot).
replace thermostat.then bleed coolant system, this is how you do it.fill the cooling coolant system with 50 / 50 dexcool and water to raise boiling point,straight water will evaporate boil away cause engine to overheat catch fire thats why you need 50 / 50 mixture antifreeze and water.to bleed coolant system first fill coolant system until coolant stay at the full cold mark on the the coolant overflow jug,then you start engine allow it to idle,place the heater and ac control in any ac setting except max and the temperature control to the highest setting,run engine until lower hose to water pump is hot. with the engine hot run the engine speed up to 3000 rpm and allow it return to idle, repeat this 5 times. slowly open the bleed valve on the thermostat housing or look for bleed valve at the water pump heater hose.open bleed valve for 15 seconds to expel any trapped air.then top off the coolant as necessary,and when top radiator hose hot thermostat open up.keep adding cooling to overflow until coolant level stop at full cold mark dont over fill coolant.if engine seem like overheating while looking at cooling gauge turn off engine wait a while until cool off add more coolant until coolant level stay stable and dont drop any.when open radiator overflow cap use large rag over the radiator cap to keep from getting scald open radiator cap a little at a time but dont open radiator cap until engine cool down first.replace the radiator overflow cap, thermostat,and engine coolant temperature sensor and check the cooling fans fuses and relays see what happens.
you need to replace thermostat and radiator cap.look under hood around engine compartment.look for a radiator cap near radiator,add 50/50 antifreeze and water to coolant system to bring up boiling point.pure water will cause engine run hotter because water evaporate away,remove radiator pour coolant in the radiator until coolant stop dropping in the radiator now some vechicle pour coolant in the coolant overflow jug,pour coolant until coolant level stop dropping and the coolant level stay at cold full mark.start engie let idle few minutes, watch coolant level in radiator if coolant start dropping add more coolant, when coolant level stop dropping put radiator cap back on let engine idle until both top radaitor hose and bottom coolant hose get warm turn off engine wait until it get cool then take a large rag slightly open radiator just a litle at a time to keep from getting scaled.once radiator remove add more coolant if low,put radiator cap back on start the engine let it idle watch the temp gauge if temperature gauge going hot zone stop engine wait until cool then add more coolant,keep doing this until engine stop overheating going into hot zone and coolant level stop dropping,make the coolant overflow jug coolant level stay at full cold mark, dont let jug run empty if so air will get in the coolant system causing engine to overheat.
Most cars have an 2 electric fans on the radiator. One will run when the coolant gets hot and the other will run when there is more cooling demand OR it will run when the AC is turned on. My guess is, the second fan is not running when your AC is. Your AC system creates heat of its own. The heat is removed through the condenser (radiator-like coil) which is usually located in front of your engine radiator. Without a fan the heat is transferred into your engine radiator causing it to over heat. This would explain why it overheats while idlling and not while driving. While driving, air is flowing through the radiator and condenser. to provide the necessary cooling. In short, check to see if both fans are running when the engine is hot and the AC is turned on.
replace the radiator cap as well and perhaps the hose to the overflow tank
Air may be entering the system causing hot spots in the engine. The radiator cap works as a valve to let coolant out of a hot engine and to draw the coolant back in as the engine cools. If the cap or hose is broken then it will allow air into the system. If your do not bleed the system properly when refilling with coolant air will be trapped in the engine causing hot spots.
I had a similar problem. Replaced head gasket, but low coolant light stayed on. My problem was air in the system. A flush and fill kit may work, however, I had a local shop do a "flush and fill" and the problem remained. What I did... With vehicle running, and radiator cap off, bring engine to operating temperature. Increase rpms slightly above idle until coolant can be seen moving in radiator (thermostat open). Add small amounts of coolant, keeping the radiator level just below overflow hole in cap area. In my case, after about 15 minutes at slightly above idle rpms, a large pocket of air escaped. I topped off radiator, installed cap, and let engine cool. Problem has not returned in last six months. *Note coolant is VERY HOT, and if rpms fluctuate, coolant will expel quickly from radiator. Also, when the air pocket escaped, coolant also sprays out. Use caution to avoid being burned.
You still have air trapped in your cooling system, turn the heat to full and remove the radiator cap with engine running, Make sure you remove the radiator cap before you start the engine, once the engine has reached it's operating temperature and there is heat coming from the vents. Top off radiator till full and place the radiator cap back on with engine still running only on the first click, make sure the coolant over flow tank is at proper level and go for a test drive with the heat still on hottest setting. (roll the windows down).
Ofter test drive 5 min to 10min, with engine still running close off the radiator cap to the second click. Tank note that the cap may be to hot so use a rag and caution not to burn your self.
This should get any air in the cooling system out, any air in the system may cause the system to burst since the air will try to escape any week spot. That's why we only close the radiator cap to the first click to prevent any additional pressure that can cause a leak from the hot air.
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Solve? Although I clicked the link to solve the problem, I have no answers but am tempted to go after honda.
Same problems still occuring on my 2003 honda civic (103,000)!
-Changed thermostat's twice (180 degree; Yes, it is correctly positoned with the jiggle tab to the top and the correct side facing the engine)
-Installed new water pump
-Checked coolant level
-Changed the timing belt
-Checked for head gasket symptoms (white exhaust, corrosion in cylinders/plugs, loss of fluid, checked cylinder compression (all check out)
-Had the entire system presure tested 3 times with no visible leaks
-Run the car for 45 minutes with no visible drips/leaks
-proped the front of the car up to get air out of the system
This weekend I had spare time on my hands so I replaced the thermostat (checked the other, which according to bioling water at 180 worked as designed) I flushed the entire system, took out the radiator and had it blown out, flushed the entire system, installed new upper and lower hoses, checked the fan switch, I will be replacing the coolant with new, installing a new radiator (since they cost only 100 online and I have the hole front end off anyway, I'll be reinstalling the fans and switches, and trying it out again.
I drive about 100-450 miles between overheating, but it is very sporadic.
Still have the same heater issues- cold air when stopped and not accelerating at times. I am tempted to check the heater core next- but there is no loss of fluid from that ethier?
When I get the system back together, I'll try running the car for a few weeks without the heat on to see if that corrects the problem.
All of the steps to repairing the cooling system seem easy and cost 1/10 of getting them checked at a shop if you have the time!