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Discussion Starter · #1 · (Edited)
About 15 miles after a timing belt change, the oil pressure light started flashing in my 2004 VW Passat. Coolant was also leaking. Towed back to garage and they replaced coolant tank. Drove it away and oil pressure light started flashing again. Towed it back and they replaced something else, something having to do with the oil pan maybe? There was no charge for either. Drove it away and light started flashing again. They said the sensor must be bad and to not worry, keep driving it, they would get back to me with a quote on oil pressure sensor. Took it to another garage who told me the sensor is working fine. Does anyone have any ideas as to what could have happened that would cause the oil pressure light to go off?
 

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There’s nothing they did mechanically to affect oil pressure. If you have the 4-cyl, it’s a fairly common problem to get a clogged oil pump inlet leading to low oil pressure. You have to drop the oil pan to fix it, and they definitely did not replace that for you for free.
Good next step: get oil pressure measure with a gage to confirm whether the sensor is working right.
 

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Discussion Starter · #3 · (Edited)
There’s nothing they did mechanically to affect oil pressure. If you have the 4-cyl, it’s a fairly common problem to get a clogged oil pump inlet leading to low oil pressure. You have to drop the oil pan to fix it, and they definitely did not replace that for you for free.
Good next step: get oil pressure measure with a gage to confirm whether the sensor is working right.
Thank you for replying. I will ask if the second garage used an oil pressure gauge when they checked the sensor. And will ask the original garage what they did if it didn't involve the oil pan. I thought that's what they had said but could certainly be wrong. It is an amazing coincidence that this flashing light began as I was driving away from picking the car up from its timing belt replacement. I have owned the car 13 years and never seen that light before.
 

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Oil pressure light and there was coolant leaking? Are you absolutely sure that it wasn't the coolant warning that you saw? Did the coolant warning ever come on? That's what would be expected once the coolant level in the reservoir got low enough. It's possible that the shop didn't refit a hose correctly, and if that was indeed the case, I'd be suspicious of the whole job.

Telling you that they replaced the coolant tank (no charge) and an oil pan (no charge) is in itself suspicious. Why change either without charge unless they broke them at the shop?
 

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Discussion Starter · #5 · (Edited)
Oil pressure light and there was coolant leaking? Are you absolutely sure that it wasn't the coolant warning that you saw? Did the coolant warning ever come on? That's what would be expected once the coolant level in the reservoir got low enough. It's possible that the shop didn't refit a hose correctly, and if that was indeed the case, I'd be suspicious of the whole job.

Telling you that they replaced the coolant tank (no charge) and an oil pan (no charge) is in itself suspicious. Why change either without charge unless they broke them at the shop?
Yes, there was a coolant leak AND an oil pressure light. Both right after the timing belt replacement. Red flashing genie lamp looking light. I never saw a coolant warning light, but I did see pink fluid pooling under the car. I checked the coolant level and it was normal though. I'm worried that I caused severe damage by driving it for the past two weeks with that warning light flashing. I have been using this shop for years with no issues and they are very highly recommended with nearly all 5 star reviews.
 

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You need to check with the 2nd shop if they have actual pressure reading on the oil. What engine do you have?
 

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If you have that pressure and you have been driving it for two weeks and you have not been hearing noises from the engine, things should be okay.

I also doubt they just replaced the oil pan for free. Thats a lot of work on just a guess. You wouldn't do that job without checking the oil pick up screen like Hirnbeiss said, because that is very likely the problem.
 

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Discussion Starter · #9 ·
If you have that pressure and you have been driving it for two weeks and you have not been hearing noises from the engine, things should be okay.

I also doubt they just replaced the oil pan for free. Thats a lot of work on just a guess. You wouldn't do that job without checking the oil pick up screen like Hirnbeiss said, because that is very likely the problem.
I have not heard anything strange from the engine. So that is good news. And yes it is very likely I am wrong about the oil pan. They mentioned oil pan several times when telling me what they had been working on, but I'm sure the two of you are right.
 

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You need to verify that you have sufficient oil flow and pressure. If not, the oil pickup screen would be high on my list of suspect issues.

How is the cam chain tensioner under the valve cover? Ever been replaced? How many miles on engine?

This is a 1.8 turbo engine, those were notorious for oil coking from the heat of the turbo when using conventional oil.
Make sure you are using VW spec oil that's 100% synthetic.

The two top things I would suspect are cam chain tensioner shoes and or burnt oil, especially if conventional oil has been used for any length of time.
The reason I mentioned cam chain tensioner is because conventional oil attacks the plastic shoes the cam chain rides on leading to deteriorating plastic that breaks off in little pieces and plugs up the pickup screen on the oil pump.
 

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28 psi is nearly 2 bar, I would be fine with 28psi at hot idle. Did they mention if the pressure readings were at idle or 2k rpm?
Do you know which oil they put in? It should be either 0W40 or 5W40. A thinner oil can cause lower pressure. Depending on your location, (like us down south), you can run even thicker oil if you don't have cold winters.

Investing in an in-car pressure gauge would be wise at this point.

Here are specs I found online from a great writeup:

Factory Oil Pressure Specifications:
Oil (not coolant) must be at normal operating temperature 80°C
Pressure at idling speed should be a minimum of 1.0 bar (14.5psi)
Pressure at 3000 RPM should be between 3.5 to 4.5 bar (50 to 65psi)


And here is the link. More info than I have ever seen on the subject:

 
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