1986 Volkswagen Jetta Sedan - Oil light on and overheats

Jetta 2 1.8 overheats new radiator new oil pump water pump new cylinder head
thermostat all new sensors. the oil light comes on when engine overheats.

Yeah, you’ve got loads of problems. I can’t help without more details. Why does the engine overheat? Or what did you THINK was the reason? What did you do to diagnose it? Is that why you’ve changed all that stuff?

Does it overheat at all time? At idle? On the freeway? Is the cooling fan running?

Have you checked for weak/bad ground connections between your battery and engine block? This was common in '80’s VWs. I had that problem with my '83 GTI, added a cable to improve the connection.

Other than the oil light and the gauge what evidence is there that it’s actually overheating?
This could be an electrical gremlin.

More info is needed. Overheats in town, on the hghway, or both?

Are you the one who replaced the oil pump in an attempt to turn the oil light off? No matter, that will never work. Logic dictates that if the oil pump is worn out then everything following the oil pump is also worn out.

I think what needs to be done at this point is to run a compression test and an oil pressure test with an extrnal manual gauge. I have a feeling that the engine is dying and there is no sense throwing more and more parts at a losing battle.


My suggestion is, since you already spent more in parts and time than this thing is worth, is to get it properly diagnosed. Then decide if the additional parts and labor is worth the cost and effort.

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Yep… What @ok4450 said…

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Something did cross my mind this morning but to avoid further guessing it’s going to take input from you. This means details about the problem. Full of oil? How are you determining that the engine is overheating? Gauge reading only or boiliing over? Etc, etc.

I do not remember details as this is ancient history but this era of VW used what was called the Dynamic Oil Pressure System and the Dynamic Temperature System. When the key is first turned on the gauges will peg out and then the warning light will flash. Properly working, they should drop back to normal but there were issues with this system. Pray it’s an electronic glitch and not a mechanical one.

For what it’s worth, a VW dealer I worked for sold a VW demonstrator to a lady and the car had 400 miles on it. She left and came back shortly with a complaint of temp gauge pegged out. The salesman told her it was the Dynamic System and it was all fine. It was not fine I found later.
No idea how but someone had poked a large hole in a heater hose and it was losing coolant badly. She never made it home. It was towed in and the engine was absolutely barbecued. Probably the worst case I’ve ever seen. Half of the exhaust valves were missing their heads due to hot corrosive engine coolant taking them off and the head itself was missing chunks between the valve seats.

The salesman got canned immediately.

OP has left the building…