Where is the location of the Thermostat for a Jetta 1999 I just need to change it cause there's no more heat coming out !!! plus, the fan(rad) does not start and the temp goes high once in a while when driving and i have to slow down and wait a bit !

u probably have air in system.need bleed air out,otherwise water wont circulate and fans will not work.check you thermostat(more likely not a problem).if that dont resolve problem,you need change water pump..let me know

sounds like your temp control sensor is not working,this sensor is located on your rad has two wires coming out of it and is easy to change, if your car is running and up to temp and the fan is not powering up this is most likely your problem good luck.

Is the fan kicking on? Radiator fan! When engine gets hot, radiator fan should kick on under the hood.
If it does, then there is a blockage in the radiator preventing it from circulating the coolant to dump the heat. Get a Rad flush.

If the fan does not kick on, then check the fan fuse and relays, usually found in an electrical distribution box under the hood. Consult your owners manual for its location and specific fuses / relays.
Possible bad fan too.. but disconnect the fan at the plug in the wiring, and test supply wire for voltage, when engine is above normal temperture.

well it sounds like your coolant temp sensor is bad that is what turns your fans on and on also since you are going to loose rad fluid when you change sensor replace thermostat to simple and cheap both thermostat usally right were the upper rad hose meets engine block aka water outlet and the coolant temp sensor is located in the side of the block also cheap and easy to change


if it helps please leave 4 thumbs up

well if you have already changed thermostat there is a few other things that can cause this they are listed below
1. faulty rad cap
2. coroded water pump impeller / replace pump
3. rad fan not coming on / possible faulty coolant temp sensor will cause this

could be waterpump?
i was going to say rad fan,but if so heater would be hot.
lack of coolant will make heater core to blow cold,if engine heats up with full coolant,usually means poor or no circulation.
water pump?
run engine with full coolant,at operating temp.with rad cap off and look in rad cap hole and see if there is movement of water inside rad.
[rad fan will not come on if water is not circulating through rad water pump?]

Flush rad & change coolant & thermostat. Check operation of rad fan, & make sure it is coming on when engine reaches normal operating temperature. Be sure to bleed air out good when refilling rad/cooling system. Start engine & turn heater on when refilling & let rad fan come on & off at least 2 or 3 times before putting cap back on rad, and refill rad as needed as you do this. then fill return bottle to proper level & see what happens.

check to see that the electric fans are turning on when they are supposed to, and make sure the coolant is full and that the rad cap is good. Bad radiator caps are one of the most common overheating causes

I will normally remove rad cap when cool. Start engine, set heater in car to heat & turn on blower, if you use defrost setting, the rad fan &/or AC fan will come on, and you don't want that. Then while running with cap off, make sure coolant in rad is an inch or 2 from top of rad, and let it run. When engine gets to normal operating temperature on the gauge, you'll start to see more flow in radiator, and rad fan should come on shortly after, to cool the incoming hot liquid in the rad, that tells you the thermostat opened as it should, and the process starts again, engine coolant gets to temp, thermostat opens, hot goes to top of rad for cooling, and cooler liquid goes out the bottom to engine, etc etc. If your heater is not on while doing this, the coolant doesn't get to heater core in most cases, thus creates an airlock, or will cause level in rad to go down when it is turned on, and thus reduces amount of coolant in rad, plus airlocks in the entire system. So, let it run to the point that the rad fan comes on & off on it's own, about 3 times, while you watch the gauge, to make sure it doesn't overheat, if it does, shut it off and let it cool down & try again. if all appears good, top rad up if needed to an inch or so from top, put your cap on properly, add coolant to proper level in return bottle & try it and see what happens. Remember though, I am assuming thermostat was put in correctly, rad in good shape, fan is working properly as well as water pump doing it's job. If this method doesn't work, get back to me with results.

you need to run the car and see if the fan comes on if it does change the thermostat and gasket if it does not you need a fan sensor