QuestionQUESTION: I have a 2000 VW Jetta GL and the heater does not work at all. The car had been overheating and leaking coolant, so we replaced the thermostat and that took care of the overheating but the leak is still there. The leak is on the left side of the engine, and it looks like it is a black metal pipe nearly touching the engine block near where the upper radiator hose connects with the heater hoses. Could you tell us what this pipe is? We can't quite isolate it or find a schematic saying what it is. Also, as per the heater, we were thinking that perhaps the sensor is at fault. Is this a common problem? if not is there anything else you suggest we check?
ANSWER: First of all...How long ago was the timing belt and the water pump replaced?
The black pipe running along the front of the engine is the "conduit" used to send coolant from the water pump to the "coolant flange" on the left side(looking forward from the drivers' seat) of the engine. The coolant flange itself is the most likely culprit for the still unrepaired leak. The thermostat was a good place to start, but there are several other items in a Volkswagen cooling system that need to be looked at, that's why my first question was about the t-belt, and water pump. If you are doing the work yourself, and it sounds like you are, then you probably don't have a hoist on which to get the car up in the air, but you have to. Get a jack, AND support the car on JACK STANDS! Don't take any chances! Inspect the back of the engine, and if you are still using the recommended PINK coolant the rear/back of the engine, all the way from the mating flange of the engine to the transaxle over, and down the differential housing at the back of the transaxle will be covered with a pink "waterfall." I'm going on the assumption that this is a 2.0L gasoline engine, and not the 1.9L TDI powerplant. The engine code for the 2.0L is either "AEG," with a throttle cable to the throttle body, or (late production) "AVH," with only a bunch of wires going to the throttle body, and NO physical connection to the accelerator pedal. (The more I think about these 3 letter codes, the more I think I may have them reversed.) Nevertheless, 2.0L engines have the waterpump under the timing belt cover, and it is run by the timing belt. My recommendation is this. (1) Replace the coolant flange, and "O" rings, (one for the flange itself, sort of an oblong shape narrower at one end), (one for the ECT), and (one for the "dummy" plug in the flange, also), and, finally, there is another "O" ring for the black pipe that runs across the front of the engine that comes from the water pump. (2) Replace the water pump. They are made of steel, but they have a plastic impeller on the back that comes away from the brass piece that has "knurling" to hold the plastic in place. To know if the water pump is necessary, have a friend help you do this part. Remove the overflow hose from the top of the coolant return tank. It's the little one. Hold the opening over the opened tank, ie. take the blue screw on cap off and watch the inside of the coolant return tank. Just hold the hose over the opening while your friend pushes the accelerator up to about 2000 rpm. If there is little, or no flow, you NEED the water pump. (3) If the water pump is necessary, replace the timing belt, and the tensioner at the same time. 2 liters' are the easiest of all Volkswagens to do, but the motormount has to be removed to get the new belt on, and if you don't have a LOT of mechanical experience, take it to a professional. Once again, your local closest/best VW dealer has the people who are trained to do this. The labor to do both the flange and the water pump, t-belt, tensioner combo should be about 5 hours total, including flushing, and refilling the cooling system. Furthermore, if you were planning on doing this yourself, you need to be able to completely evacuate the cooling system to remove bubbles in cavities in the hoses, and engine block that CAN NOT be filled with a jug, and a funnel, and there is no provision for air lock release through a fitting at the top of the cooling system like there is in a Land Rover, or a Nissan. The second problem you describe about no heat from the heater sounds like you already did the coolant drain, but not the vacuum refill of the cooling system, to me.
To properly evacuate the cooling system it is necessary to have access to "shop air," if you have a 20 gallon or larger air compressor, that should be large enough, but there is a special tool, available only from, "MAC," "MATCO," "CORNWELL," or the like. You can't just buy the Volkswagen one. It is a proprietary tool, and they won't sell it to the general public.
Anyway, there is a gauge on the funnel shaped black rubber fitting that goes into the reservoir tank/return tank, and once you have the shop air hooked up, you need to let the gauge go into the green as far as your air compressor can send it...usually an atmosphere and a half or more...like 1.5 bar or more. Remove the air adapter form the funnel fitting with the valve CLOSED, or all the vacuum escapes, and you have to start over. Then place the filling hose with the filter end in the gallon jug of coolant, you will need the better part of 2 gallons to fill the system. Close the valve as you switch jugs, and open again when it is in the fresh one..., as the second jug begins to get to the bottom, pour the remaining little bit of coolant from the first into the second, and by then you should be full. The special tool is a little less than $200.00, but can be used in lots of unusual cooling systems, and can also be indispensable in tracking down leaks, because if it won't hold a vacuum, it won't hold coolant either....I think the tool name is "AIR-LIFT." I don't know if it is one word or two, and I don't know if it is hyphenated or not. I do know they are available. Once again, good luck in your quest for repair. I usually get the air out down to 1.5, to 2 bar, and then close the system completely, remove all hoses from the special tool, with the valve closed, and wait 5 minutes or so. The needle can move, but only a little tiny bit, if it is a significant amount, further diagnosis is required, and furthermore when the new flange, ECT, dummy plug, and supply tube are all installed into the new flange be certain that the mating surfaces are clean, clean, clean, and the "O" rings are generously coated with petroleum jelly to help them seal, and slide together without misalignment.
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QUESTION: okay, thank you very much. You have been more than helpful. We tested the water pump and it is fine, so it seems like I was correct in assuming that the previous owner did have it replaced along with the timing belt. We will replace the o-rings, vacuum fill the system and see what happens. Once again you have been a great help, thanks a lot.
AnswerI'm glad the water pump is good. However, I would be remiss if I didn't add that tbelt/WP replacement intervals are suggested for 105,000 miles, so if bought at 83K, you might be approaching the magic number, anyway. Look at the belt and feel for tension on the back side of the belt, if you can easily push it with one finger then it might be a good time to consider its' condition. I don't want to frighten you, or dissuade you. I only report facts from my perspective, and without being able to examine the car personally, I don't want to see you, and your friends, and helpers invest a lot of effort, and time, and resources into a repair that lives for only a short period of time. Is it possible to contact the previous owner? Just to find out for sure when the tbelt/WP were done last. No matter what, I'm glad that the information given has been of assistance, and I mean it when I say good luck in your quest for "repair."
