Overheating Engine?

A stuck closed thermostat will prevent coolant flow-try without it and see what happens. Continues to overheat please go over this guide to help fix it.

https://www.2carpros.com/articles/engine-overheating-or-running-hot

Please run down this guide and report back.

I have a 99 Volkswagen Jetta that has been intermittently overheating. I have checked for fluid leaks, but found none. What are possible things that could be only working intermittently and failing at other times to cause this problem?

Electric radiator fan that doesn't turn on will cause overheating at slow speeds but not on the highway where there is plenty of air flow. Leaking head gasket can cause an air bubble in the cooling system. That could cause the thermostat to not open and allow hot coolant to flow to the radiator. Thermostats only open in the presence of hot coolant, not hot air. Your mechanic has a tool for testing at the radiator cap for a head gasket leak. Volkswagens have had some problems with the flimsy plastic water pump impeller breaking free and failing to circulate the coolant. The clue is there will also be cold air coming out of the heater.

My car started overheating yesterday while I was driving and the coolant cap blew,I noticed the coolant fans don't I already checked the fuses and there fine, when I poured coolant it drained quickly and I noticed a leaking in the middle left side of the car, my account doesn't work and the heater works when it wants to any suggestions?

put a water hose in the radiator and turn it on so you can determine where the leak is first

Is your car a mk3 or a mk4 jetta?

There is no opening on the radiator, just an upper hose and a lower hose.

There are a lot of plastic fittings on these engines... because your engine overheated, one or more of these plastic components / fittings are probably broken.

Common issues:
- the plastic coolant flange that mounts to the side of the cylinder head, it contains the thermostat
- the plastic coolant pipe that runs from the water pump to the coolant flange on the side of the head (where the thermostat is)
- the electric coolant pump sometimes break
- the plastic fittings at the heater core hoses break

Thermostat housing replacement on a mk4: Removal
www.youtube.com/watch?v=3SVYfaHHl8g

Installation:
www.youtube.com/watch?v=Q4y-s4s6ebY

Guess it's not overheating anymore....

I have a 1999 jetta VR6 that has a problem with puking out the antifreeze. I can drive it all day and not have a problem and then when I get up in the morning the antifreeze is on the ground. The temperature never gets hot. The car runs good. We were told to oil the cap on the tank, but we got a different cap and noticed that he gasket was gone on the old one. We put the new cap on and it worked really good for a week, then started again. We took the round tank off and found the gasket from the old cover in the tank and got that all out and reattached the tank and filled up with antifreeze. We let the car run for about 20 minutes and shut if off. I got up the next day and the antifreeze was on the ground again. I drove it yesterday about 60 miles and came home. I looked out about two hours later and the antifreeze was on the ground again. I am just so frustrated by this. This started last summer (2010). We would not drive the car for two days and then start it up and pull out of the driveway and shut it off and it would do it then, but never while driving it. What could be causing this problem? Please help.

Coolant leaks can occur in several places, and coolant can leak at
different times, depending on engine temperature.

Usual items that are responsible fore leaks:

- water pump
- plastic thermostat housing that is bolted to engine block under
the ignition coil pack
- radiator

When standing in front of the engine:

- If coolant is leaking on the left side, the water pump is leaking
- If coolant is leaking on the right side, the coolant flange on the
side of the engine block is leaking.

The radiator can leak at either the left or right edge, so it is
best to try and trace where the coolant is coming from, before
ordering & replacing parts.

Thomas

My Car Overheats When A/C Is On

Have an inspection of your cooling system done first. Check the level, pressure test for coolant leaks, test the thermostat, check to see that the cooling fans are coming on at the proper temperature.

Coolant was leaking from the top heater hose where it connects to the engine. I removed the hose trimmed the end and reattached it losing a small amount of coolant in the process. I topped off the coolant in the reservoir and drove about 10 minutes before the car overheated. This car had never overheated before. I also had no heat coming from the heater. I was told I may have air in the system. I decided to drain the system and replace the coolant. Jetta has no drain plug on the radiator. I removed the bottom radiator hose, drained and flushed the radiator. I replaced the hose and attempted to refill the system through the coolant bottle. Jetta radiator has no cap. The coolant would not go into the system till I removed the top radiator hose to allow air to escape. I filled till coolant came out the top hose, then reattached the hose. The car is still overheating, and no heat from heater. I was told to alternate the car between idle and 2500 rpm for 20 minutes with the coolant bottle cap off and no pressure on the system till the air bled off. I did this and the heater began blowing hot air, the heat gauge was in the normal position of 190 degrees, but the engine was so hot the oil light came on! I am at a loss as what to do next. Help?

Run it w/o the thermostat and tell me what happened this is where we start-get back soon so that we can continue. Or do below

Have it block and pressure tested-do the block first to pinpoint a combustion leaking into the cooling system or a gas analyzer to sniff for hydrocarbons at the radiator fill neck.

Pressure test: do not do a pressure test if there's leakage at the headgasket this might cause coolant into the cylinders and lock it up or bend a connecting rod if cranked thereafter. The headgasket should be repaired before doing the pressure test.

If the block and pressure test passes check the following: ,Pressure test the Rad. cap,Clogged radiator,air lock in the cooling system ,Fan clutch,Radiator electrical fan,collaspe hoses,water pump.

To access the thermostat, it is necessary to remove the power steering unit and fan belt. I would rather not do this. When I removed the heater hose and replaced it, I introduced air into the system. My research tells me Jetta is notorious for this problem, but finding fixes is difficult. Lets assume the problem is air in the system. how do I get it out? Jetta has no drain plug and no radiator cap...

When refilling the cooling system, air can become trapped under the thermostat. This will form a steam pocket that prevents the thermostat from opening and may cause the engine to overheat. Some cooling systems have one or more bleeder valves that can be opened to vent air from the system while refilling the system. If your cooling system does not have a bleeder valve, you can drill a small hole in the thermostat as shown. This will allow air to escape past the thermostat so it is not trapped inside the engine block. Some thermostats come with a similar feature called a "jiggle valve." There is a small hole in the thermostat with a pin that allows air to escape.

Engine Cooling problem
1994 Volkswagen Jetta 4 cyl Front Wheel Drive Manual

my jetta with a 2.0 engine overheats,has no heat and the coolant fans will not kick on?

First thing would be to check coolant levels, then for air bubbles. I'm thinking you have a leak somewhere in your system. Rent a pressure tester (after filling up your coolant) and check for leaks. The fans aren't coming on because they are not sensing any of the overheated coolant.

I had a overheating problem and already change water pump,thermostah,fan switch in radiator,and flushed the cooling sistem,fans start working but stil is overheating,a friend of mine toll me, about a air burble inside the head,how can i fixed? thank you.

Try bleeding the cooling system.

Always bleed air from cooling system after replacing coolant. Set heater for maximum heat. Remove radiator cap. Loosen drain plug and remove drain bolt (if equipped) from engine block. Drain coolant reservoir. Fill coolant reservoir to MAX mark with 50/50 water-coolant mixture. Loosen bleed bolt and fill radiator up to base of filler neck. Close bleed bolt when coolant flows out without bubbles. Tighten bleed bolt. With radiator cap removed, start and operate engine to normal operating temperature. Add coolant if necessary and check for leaks.

My 1992 VW Jetta is overheating and there is hot steam coming from the air vents when the heater and air system is off. whats wrong with my car?

I would say that the heater core has failed, a cooling system pressure test will prove this one way or the other.

mark (mhpautos)

Thanks Mark I kind of felt it was but wanted a reassured answer.

While driving I noticed the temperature gauge was reading very high, so I pulled over and coolant was coming out of the expansioin bottle. I removed the stat. and topped up with water. It continued to overheat.
When I got home, I ran it until it overheated and noticed that the cooling fan only kicked in as coolant started to come out of the expansion bottle. So I replaced the thermal switch. Drained and flushed the system - all appears clear. Refilled system - ran it two/three times heat up - cool down to get rid of air pockets. Took it on the road maybe 5/6 miles stopped and let it running, it was bubbling slightly not bad thought it might be air. Returned home and let it cool down. Topped up when cool - 2pts. Now runs fine maintains proper running temp while driving but once I stop the engine coolant starts coming out of the expansion bottle. I've disconnected the overflow piipe to the top of the expansion bottle and got someone to bring the engine up to 3000rpm and coolant squirts out. I was told that this wouldn't happen if my water pump wasn't working. Help!!! I'm at my wits end. The model is a VW Vento a variation of the Jetta that VW brought out over here in Europe. It's got a 1.4ltr engine.

Have it checked for a blown head gasket.I have seen many vehicles that would be fine until they were driven then they would get hot and spit out coolant and even overheat if still driven.Especially if it is using coolant (low without spitting any out). Your local shop should be able to do a chemical test for you to see if there is any exhaust present in the cooling system for a reasonable price, the test isnt 100%, but it is real close

Heater problem
1991 Volkswagen Jetta 6 cyl All Wheel Drive Automatic unknow miles

My car has overheated a couple times and is at the point where it might overheat again. When I see the the thermostat go up I crank up the heat causing the thermostat to back to normal.

I don't know much about cars but I know the thermostat has been changed.

Any ideas on what's wrong?

Thanks

Because you have overheated the vehicle the thermostat is now no good, what I would do is have the thermostat removed and drive it and see if it continues to overheat, since you have to replace it anyway. You may have a bad water pump or plugged radiator, but to start our diagnosis, lets start by removing the thermostat and see if the problem continues.

I am having the same problem it keeps overheating.

I have removed the thermostat and it still overheats

what do I check next???

the only thing I can think of now is you have a blown head gasket, remove your spark plugs and let me know if any of them are wet.

plugs are not wet, what do I check next?

OK, is the radiator fan coming on when it gets hot? if it is, you are going to have to go to your local parts store preferably Harbor freight, and purchase a infrared temperature gauge so you can check the temperature on the upper radiator hose and the lower radiator hose to make sure you are getting flow through the radiator, and let me know.

How is the coolant level?

Before you do anything invasive, such as paying for a head gasket, try a full rad flush. Or just topping up the antifreeze or adding some water wetter.