I have a 97' 4Runner ... when I turn on my heater initially hot air comes out but gradually cools down ... I took the truck in (scheduled PM) to have the timing belt replaced, I also had the water pump,thermostat and all the other belts replaced. I still have the heat issue! The only thing left is the heater core, but I have no symptoms of a bad core (no leak,no smell, no foggy windows) ..... is it possible that it's something else????
Does the temp gauge fluctuate?
It might be as simple as being low on coolant. When the engine is cold, check your coolant over-flow tank level and remove the radiator cap and check the level in that.
I'm certain it's not the heater core.
Flash .... Thanks for your reply ..... when I had the Timing belt/water pump/termostat done the system was filled with fresh antifreeze ... it seems to take longer for the truck to get hot but the guage stay's dead center once it does .... ... when the engine is cold the radiator appears to be full, but the over flow tank is empty?
Flash .... Thanks for your reply ..... when I had the Timing belt/water pump/termostat done the system was filled with fresh antifreeze ... it seems to take longer for the truck to get hot but the guage stay's dead center once it does .... ... when the engine is cold the radiator appears to be full, but the over flow tank is empty?
OK Tom, that makes sense. Again, when the engine is cold, remove the radiator cap, top off the antifreeze and then fill the over-flow tank to the "cold" level and recheck after the engine is warm/hot.
The level in the over-flow tank should be at the hot level when "hot", if not top off.
Any air in the system will give you the results you are mentioning....
Good luck!
OK, With the engine cold, the radiatior was full, the overflow tank wasnt exactly empty (had about 2 inches in it) I filled the overflow to the 'F' .. ran the engine .... no change.. engine guage comes up to temp, HOT air comes out but then gradually cools off (within 30 seconds) , it never gets 'cold' but still not good ..... if I shut off the fan, wait a min then turn it back on it is HOT again! When the engine is hot both levels are good and top radiator hose is hot (as it should be) .........
When the engine is at operating temp (hot), check the temp of the heater hoses going into the heater core (at the firewall). With the heater control set at "heat" and blower motor set at "low", the temp of both hoses should be very close to the same. You can do this by feel but be careful as you don't want to get get burnt by the hose temp.
Also, check the temp of the upper radiator hose with the engine at normal operating temp...again be careful.
If the temp of the upper radiator hose is not at or about the t-stat rating (around 190 degrees) then you might have a weak or defective t-stat.
The temp of the heater hose (input side) should be very close to the temp of the upper radiator hose.
Then, turn the fan speed up and see if the temp is still somewhat the same in both heater hoses.
OK, I let the engine warm up ... I can wrap my hand around the top radiator hose and hold it there, it's hot, but no where near hot enough to burn me ... it was hard to tell if the hoses going into the firewall were the same temp as the radiator hose, but again they were not hot enough to burn me ... Maybe I got a new defective thermostat? (or the mechanic didnt really change it??)
Tom, do you have the bill of sale? If so, does it state a new t-stat was replaced? Like you said though, you never know.
How long did you drive the truck before you checked temp at the upper radiator hose?
I'd drive it at least 5 miles (depending on outside temp) and then check. On a 195* t-stat you shouldn't be able to hold your hand there for very long.
And that's the t-stat you should have installed....a 195* that is.
I ran the truck at least 10 miles it was about 33 today ...... heat ran 'warm' the entire time on low ..... I don't have an official 'receipt' from the mechanic as it was a 'cash' deal, but my best friend has been taking all of his cars to this guy for years .. he even uses him for his business vehicles ..so I trusted him .... ... so I guess I either go back to him .. or try my luck somewhere else ... I just don't trust these F's ... Thanx for your help !!
Tom, I probably do a t-stat....I've seen them defective, brand new right out of the box.
Make sure all air is bled out of the system afterwards.
Good luck!
Tom, as you can imagine it's rather hard to diagnose over the "net" so I'm just giving advise and suggestions on the obvious things.
Giving you ideas and then having you follow through with them is the only way I can help but I also don't want you throwing money into it uselessly.
Does your tech have an Laser Temp Gun? This uses 2 laser beams directed at an object to detect temperature. This would be very useful in diagnosing your problem. It can check the temp of the radiator hose coming out of the t-stat housing, the temp of the lower radiator hose and the temp's at the heater hose's going into and out of the heater core.
The temps need to be checked to fully diagnose this problem.
Good luck!
No, he doent have a temp gun. He spoke with his buddy @ Toyota ... the Toyota guy had him #1 check the duct damper/diverter under the dash, it was operating like it should #2 he bypassed the heater control valve on the input side of the core ..same symptom .... So it comes down to the water pump or the heater core .. I had this issue prior to having the water pump changed, so I'm ruling the pump out ..... Sooooo I'm going to have him flush the core, ($50..)hopefully that will do it .... if not, I guess I'll have to dress warm while driving! Spring is right around the corner!!
Radiator and heater core tube plugging due to mineral deposits and coolant gelling is possible if aftermarket antifreeze, tap water or coolant additives were ever used in the system. Independent shops use aftermarket water pumps, thermostats, thermostat gaskets and coolant so ultimately the source of your "insufficient heater core heating" problem will be traced to aftermarket parts or fluids the former owner or an independent shop used to service your vehicle.
Of course, no shop would admit this and they might also say "a heater core is subject to plugging after 10 years no matter what coolant mixture was used" so don't expect any financial reimbursement for the trouble they caused you.
To avoid future trouble of this nature, use the parts and fluids Toyota installed in your vehicle before it left the factory; i.e. a toyota brand 180 degree thermostat and thermostat gasket, toyota water pump, toyota red long life antifreeze and distilled water.
Well, I thought I'd post the solution to my 'no heat' issue ... AIR ..... I took the truck to my guy who does all of my tire/brake/suspension work .. he blew out the heater core out with AIR (he said it was an 'old trick') ..... it's fixed ..... it's blowin heat like a &*$ of a (*&*%$ .... ... now it's time to focus on the boat ! Wooo Hooo
1997 4Runner heat issues
Maybe I got a new defective thermostat? (or the mechanic didnt really change it??) 
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