Check to see is water circulating top and bottom hose should feel the same temp, if not change thermostat.
SOURCE: VW Passsat - 98 -
First check the coolant overflow and add a little water if low (if you have antifreeze then a pint of water will not dilute it enough to matter).
Go to a parts store that will plug in and read the OBD II codes for free (autozone among others). My dealer change $50 just to read the codes. BTW you can buy a simple VW code reader for $50! ABS system will give specific codes as to what is wrong. Coolant warning light is usually either low coolant in resevoir or overheating. If the coolant light comes on when you first start up, it's probably just low coolant level. My wifes 98 Passat and my 2005 Jetta TDI both did this for a slightly low coolant with no detectable leak.
If you have to add coolant more than once, you may have a small internal leak (read in the cylinder head) which you will not be able to find. A Mechanic can do a pressure leak down test to find out. This is one of the 2 times in 35 years where I used Barr's Stop Leak on our 98 Passat with 120K miles for this slow internal leak symptom ... it's 20K miles later and I have not had to add coolant since the Barrs. I generally hate these fix it in a can type products, since many of them are snake oil, but Barrs can work without side effect in some cases. I have it from a reliable source that the manufacturers use a smiliar substance on new engines now that most cylinder heads are aluminum, but I have no way to verify.
good luck
..ajm
SOURCE: 2001 VW PASSAT OVERHEATING
they changed the thermostat, water pump, flush it down, timing belt, but still overheating my VW passat 2001, what is the problem
SOURCE: 04' Passat Overheating
Hi!
It
appears we have an Air lock scenario and you will need to perform a
system Bleed.
Park
the vehicle on level ground, when cold remove coolant filler cap,
start engine and leave to idle, turn heater on full and blower to
max. When engine reaches operating temperature watch and listen near
coolant filler, keep clear as gurgling and hopefully a boil over
should occur. Top up with very warm coolant and wait as it may do it
again.
Check
for heat inside vehicle if warm replace coolant cap but keep an eye
on temperature gauge as the ~Air lock may have moved on from heater
matrix/core so proceedure needs to be carried out again from COLD.
If
persistent boil ups/over attention must made in the cylinder head
or
gasket area, or possibly water pump?
Please
press the Blue button to appraise my FREE Efforts, Thank You!
Paul
'W' U.K.
SOURCE: oil in water resovour vw 2002 passat
This is probably a head gasket problem and not an oil cooler problem.
The oil cooler is fairly easy to test.
Remove the cooler from the engine but do not disconnect cooling lines and then pressurize the cooling system. You can use a radiator test tool to put pressure on the cooling system and look for leaks. If it leaks, replace it.
You may also be able to bypass the oil cooler altogether if it leaks.
The head gasket is another story.
Get a 1/4" pipe to spark plug fitting and put a male air coupling fitting in it.
Then you can charge the cylinders with air from your compressor.
Make sure each cylinder that you test is at top dead center so that the valves are closed.
If air bubbles into your coolant, you found your problem.
If air leaks out your intake you have a bad intake valve
If air leaks out your exhaust you have a bad exhaust valve etc.
If you find this useful, please take the time to rate it.
Tim
Overheating can seriously damage a car's engine if left unchecked. Although overheating simply means that a car's engine temperature exceeds normal operating temperatures, the causes of overheating are varied. What follows is a brief list of some of the most common causes of engine overheating.
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