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Overheating Engine?

Tiny
FRANKHV
  • MEMBER
  • 1999 VOLKSWAGEN JETTA
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 140 MILES
Just replaced the waterpump and timing belt, bent exhaust valves and head gasket and thermostat. Car runs again but still overheating!

99 Jetta 2.0L, w/AEG engine, automatic.

The new waterpump has a metal impeller, old one had a plastic one. Car warms up and gauge goes to 190degrees after car runs for awhile and then car shuts off (I'm assuming because computer sensed a max temp for engine?) Anyways, what gives here? I did add about a gallon of antifreeze and I see no leaks.

The upper radiator hose is hot but the lower one, which comes from the thermostat is basically cold - not even warm.

I also changed out the thermostat while replacing the waterpump and I installed it the right way - spring side toward engine.

I did open the drain at the lower hose - coolant comes out fast then slows way down. Each time I do this it repeats - fast then slow to a trickle. Is there a valve somewhere else to purge air out of the system?

As I said, the water pump is new w/metal impeller. Before I installed the timing belt I turned it and it spun w/out any resistance.

Would a stuck thermostat prevent coolant from circulating in this car?
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Saturday, June 25th, 2011 AT 9:45 PM

31 Replies

Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
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.
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Saturday, June 25th, 2011 AT 10:39 PM
Tiny
DIXIEMOMOF3
  • MEMBER
  • 1 POST
  • 1999 VOLKSWAGEN JETTA
  • 4 CYL
  • FWD
  • MANUAL
  • 168 MILES
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?
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Monday, July 27th, 2020 AT 4:32 PM (Merged)
Tiny
CARADIODOC
  • MECHANIC
  • 33,916 POSTS
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.
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Monday, July 27th, 2020 AT 4:32 PM (Merged)
Tiny
JUANB
  • MEMBER
  • 1 POST
  • 1999 VOLKSWAGEN JETTA
  • 2.8L
  • VR6
  • FWD
  • AUTOMATIC
  • 169,000 MILES
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?
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Monday, July 27th, 2020 AT 4:32 PM (Merged)
Tiny
KNOWLEDGE IS POWER
  • MECHANIC
  • 1,136 POSTS
Put a water hose in the radiator and turn it on so you can determine where the leak is first
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Monday, July 27th, 2020 AT 4:32 PM (Merged)
Tiny
EXOVCDS
  • MECHANIC
  • 1,883 POSTS
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
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Monday, July 27th, 2020 AT 4:32 PM (Merged)
Tiny
EXOVCDS
  • MECHANIC
  • 1,883 POSTS
Guess it's not overheating anymore.
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Monday, July 27th, 2020 AT 4:32 PM (Merged)
Tiny
KIM5611
  • MEMBER
  • 1 POST
  • 1999 VOLKSWAGEN JETTA
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 122,000 MILES
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.
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Monday, July 27th, 2020 AT 4:32 PM (Merged)
Tiny
EXOVCDS
  • MECHANIC
  • 1,883 POSTS
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
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Monday, July 27th, 2020 AT 4:32 PM (Merged)
Tiny
DOCRONI1
  • MEMBER
  • 1 POST
  • 1998 VOLKSWAGEN JETTA
  • 128,000 MILES
My Car Overheats When A/C Is On
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Monday, July 27th, 2020 AT 4:33 PM (Merged)
Tiny
F4I_GUY
  • MECHANIC
  • 3,302 POSTS
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.
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Monday, July 27th, 2020 AT 4:33 PM (Merged)
Tiny
MLHOPE
  • MEMBER
  • 2 POSTS
  • 1997 VOLKSWAGEN JETTA
  • 4 CYL
  • 2WD
  • MANUAL
  • 121,000 MILES
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?
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Monday, July 27th, 2020 AT 4:33 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
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.
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Monday, July 27th, 2020 AT 4:33 PM (Merged)
Tiny
MLHOPE
  • MEMBER
  • 2 POSTS
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.
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Monday, July 27th, 2020 AT 4:33 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
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.


https://www.2carpros.com/forum/automotive_pictures/12900_thermostat_bleedhole_1.jpg

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Monday, July 27th, 2020 AT 4:33 PM (Merged)
Tiny
EDDIE133
  • MEMBER
  • 1 POST
  • 1994 VOLKSWAGEN JETTA
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?
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Monday, July 27th, 2020 AT 4:33 PM (Merged)
Tiny
TREES
  • MEMBER
  • 14 POSTS
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.
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Monday, July 27th, 2020 AT 4:33 PM (Merged)
Tiny
TLAQUILELE
  • MEMBER
  • 1 POST
  • 1993 VOLKSWAGEN JETTA
  • 4 CYL
  • FWD
  • MANUAL
  • 170,000 MILES
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.
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Monday, July 27th, 2020 AT 4:33 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
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.
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Monday, July 27th, 2020 AT 4:33 PM (Merged)
Tiny
KYNANB1
  • MEMBER
  • 2 POSTS
  • 1992 VOLKSWAGEN JETTA
  • 4 CYL
  • FWD
  • MANUAL
  • 140,000 MILES
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?
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Monday, July 27th, 2020 AT 4:34 PM (Merged)

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