Verify that the FAN is working properly. Do a coolant flush and ask your VW mechanic to do an inspection on all hoses + a sanity check on the water pump, which more likely is the culprit.
Over heating
Hi Guys. First post. 2003 Jetta 2.0 engine. 175 miles. Owned car for 6 months. First couple months no issues. Then overheated (gauge all the way to red). Gas station mechanic changed a couple hoses and the thermostat/housing. Said the PO must have used a stop-leak additive. Found some gunk in the system. Car didn’t overheat for two months, then started to again.
Symptoms: can idle in park for 30-40 minutes then start to overheat. Driving, will overheat within 5 miles, to the red or near to it. Both fans come on high when the needle gets beyond one mark right of 190. Both fans come on low (when not overheating) when I turn the AC on. I have heat and AC in the cabin. The only thing that lowers the temp back to normal is putting it in park, reviving to 3k, in which case the needle goes to normal within minutes, then returns to the red upon driving just as quick.
I’ve changed the thermostat (and tested it) and the blades of the water pump were in tack. I’ve also seen water being pushed through the upper radiator hose. I’ve changed the radiator heat switch and the fan control module (I took it to the dealer and they said those parts were defective). I’m running it with VW coolant. None of this has made a difference. Also, there’s no oil in coolant, water in oil and there’s no white smoke coming from engine. The car runs great and appears to have been well cared for by the PO.
Any ideas?
Many thanks.
Symptoms: can idle in park for 30-40 minutes then start to overheat. Driving, will overheat within 5 miles, to the red or near to it. Both fans come on high when the needle gets beyond one mark right of 190. Both fans come on low (when not overheating) when I turn the AC on. I have heat and AC in the cabin. The only thing that lowers the temp back to normal is putting it in park, reviving to 3k, in which case the needle goes to normal within minutes, then returns to the red upon driving just as quick.
I’ve changed the thermostat (and tested it) and the blades of the water pump were in tack. I’ve also seen water being pushed through the upper radiator hose. I’ve changed the radiator heat switch and the fan control module (I took it to the dealer and they said those parts were defective). I’m running it with VW coolant. None of this has made a difference. Also, there’s no oil in coolant, water in oil and there’s no white smoke coming from engine. The car runs great and appears to have been well cared for by the PO.
Any ideas?
Many thanks.
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Thanks. I would assume it’s the WP although both I and the dealership tech thought it works as expected to. Other than feeling/wiggling blades (no movement) and observing the water flow into the upper hose, how else could it be checked?
Just did a more in-depth visual of the hoses. Saw this, posted below. This is a pair of hoses, one of which is coming from the place where the thermostat/water pump is (not the big radiator hose). Looks like they melted together, or, the hoses come as a set. Can anyone confirm? I’m trying to find if there’s a blockage but this looked suspicious. Many thanks.
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You need to replace those hoses that will obstruct the flow! Check the flow of the reservoir as well as this video shows. (2) VW A4: Overheating 2.0L quick checks as to why (first 3 min) - YouTube
Thanks. I’ve seen the video and I do have flow at the bowl from the return line. Can someone identify those hoses so I can order them, or can I just use any appropriate coolant hose that fits?
Thank you.
Thank you.
Nevermind my previous REPLIED, you got it.I think I just found it, although this is for a 1.8 and mine is a 2.0. On any account it appears they are connected so my hose is probably fine. View attachment 38662
Thanks for the reply and the diagram. Planning on removing every coolant hose one by one and inspecting.
I believe the MK4 hoses are “fused” And that is normal. Your hoses appear pitted and should be replaced forthwith. My experience with several Jetta 2.0’s is after about 15 years, once you replace one hose or connector you will have to replace another within weeks. I HIGHLY recommend replacing all the hoses and plastic coolant connectors at once. That will rule out blocked hoses and they may be collapsing under load-they don’t look great.
Check the Radiator Cooling Fan Control Module. It is typically under the battery tray and easier to access from under the car. MAKE SURE you get the exact part number if you replace it! There are many that will “fit” but do not work properly. I have learned this the hard way. Electric items should always be OEM, not auto zone or whoever.
ECSTuming sells , or used to, entire cooling system hose kits. I would think other good vw part suppliers do as well.
Check the Radiator Cooling Fan Control Module. It is typically under the battery tray and easier to access from under the car. MAKE SURE you get the exact part number if you replace it! There are many that will “fit” but do not work properly. I have learned this the hard way. Electric items should always be OEM, not auto zone or whoever.
ECSTuming sells , or used to, entire cooling system hose kits. I would think other good vw part suppliers do as well.
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