Hot, hot day, low oil pressure - Follow up

[theoldkid]

For those of you that read my original thread, you know that I was going to try a new dual oil pressure sender, the one that mounts on the head. I tried it yesterday. Just as my mechanic who tried it originally told me, it doesn't work correctly. The low oil pressure LED flashes constantly at idle when it is installed. The p/n for this new unit is 035919561A and is rated at 0-5 bar and 1.8 bar.

I think the dual unit I actually need is rated at 0-5 bar and 0.3 bar. German Auto Parts have them for about $50.

My car only has 2 oil pressure senders. the other one is the high pressure sender mounted on the oil filter flange is p/n 056919081E, has white insulation, and is rated at 1.6 - 2.0 bar. I think this is the correct one for that location.

My setup is a little peculiar in that there is no oil cooler between the oil filter and the oil filter flange. In addition, there is no second allen bolt on the filter flangle that can be removed in order to install a second single oil pressure sender for low pressure. I thought about doing that rather than buy the more expensive dual sender, and then leave the old existing dual sender installed but connect the wire originally connected to WD on the dual sender and reconnect that wire to the second single low pressure sender. However, without a place to screw it in, that is not possible. So I will be buying a dual oil pressure sender with the low rating of 0.3 bar.

Please let me know if I am mistaken in anything I said in the above, and thanks very much.

[arek555]

I am experiencing the same problem, my oil pressure light flashes whil the car is idling if i just gently touch the gas pedal it goes away, i know the oil pressure is fine, I want to replace the dual switch as well, so your saying i would have to get the switch rated at 0-5 bar and 0.3 bar ?

[theoldkid]

I think so, but actually that is what I am trying to find out. It would also be nice to know which dual sender is for which vehicle. Very confusing, to say the least.

[theoldkid]

Anyone??

[Black_cabbie]

Did you actually measure the pressure with a reliable meter? It could be that you have a low pressure at idle.

[tolusina]

James,

It looks like you have done your homework, all looks correct.

May I add your post above to
http://reflectionsandshadows.com/cabby/dopws.html please?

Ron

[tolusina]

Eric,

Read this......
http://reflectionsandshadows.com/cabby/dopws.html

Ron

[theoldkid]

Thanks, coming from you - that is exactly the reassurance I need, and yes, please add it to your referenced html.

[theoldkid]

But I am still wondering what the heck the 035919561A dual sender is used for? It is the one that is rated at 0-5 bar and 1.8 bar.

[theoldkid]

Anyone know??

[tolusina]

James,

Quote, originally posted by theoldkid »

But I am still wondering what the heck the 035919561A dual sender is used for? It is the one that is rated at 0-5 bar and 1.8 bar.

A quiz, EH?

There were some models that didn't use the low pressure switch at all, only the high pressure switch. The 0-5 bar section of that device is the variable resistance sender for the oil pressure gauge, the 1.8 bar section is for high pressure sensing function of the Dynamic Oil Pressure Warning System.
The best I recall is that system was used on U.S. produced GTIs (sometimes considered Rabbit GTIs).

I'll be changing the reference page soon, maybe tomorrow, this bit is going in too! Thanks!

Ron

[kamzcab86]

ETKA, the VW parts catalog, says:

035919561: 0-5/0.3 bar; 2 pin, natural

035919561A: 0-5/1.8 bar; 2 pin black; for vehicles with electronic control unit (printed circ.) for oil pressure warning light

To add to the confusion, mine looks like the A" version, but has "0.3" printed on it:

Looks like ETKA may be slightly off .

[theoldkid]

Thanks for the info. It is, as you say, confusing. The single oil pressure switches are even worse. Apparently the colored insulation is related to specific pressure ratings, but I have seen black ones, white ones, brown ones, and blue ones. I wish there was a list that correlated the color to the rating. Or does the color even mean anything?

[theoldkid]

Thanks, Ron. With your help some of this is starting to make some sense.

[Moljinar]

Quote, originally posted by theoldkid »

Thanks for the info. It is, as you say, confusing. The single oil pressure switches are even worse. Apparently the colored insulation is related to specific pressure ratings, but I have seen black ones, white ones, brown ones, and blue ones. I wish there was a list that correlated the color to the rating. Or does the color even mean anything?

Not only are the ratings different but some are normally open contacts and some are normally closed.

[theoldkid]

Oh, no, not another complication! And just when I thought I was getting a handle on the subject.

[Moljinar]

Well, at least they're consistent. If a black one is normally closed then all the black ones will be, etc.

[theoldkid]

I think you are correct. Today I finally got around to testing the pressure with a good testing gauge. I removed the oil pressure dual switch at the head and connected my testing gauge there.

With the transmission in park and the engine hot (I let it run at various RPMs for about 15 minutes to get the engine hot), here are the results:

idle (about 800 RPM) ---- 0.5 to 1.0 Bar
1000 RPM ---- 1.0 Bar
1500 RPM ---- 1.5 Bar
2000 RPM ---- 2.0 Bar
2500 RPM ---- 2.8 Bar
3000 RPM ---- 2.8 Bar
3500 RPM ---- 3.0 Bar
4000 RPM ---- 3.0 Bar
4500 RPM ---- 3.0 Bar
5000 RPM ---- 3.0 Bar

Then I immediately removed the oil pressure tester and screwed in a new dual Oil pressure tester rated at 0 - 5 Bar and 0.3 Bar. After starting the engine back up the VDO oil pressure gauge agreed with the oil pressure tester readings, and of course the idiot light blinked at idle.

As I mentioned in an earlier thread, the engine has a new oil pump, new main bearings, and the correct oil filter. It has 20W50 oil.

Do I have a serious problem, or is the idle speed just too low? I can rev the engine up to 1000 rpm and the oil pressure is within specs and the idiot light does not blink.

Thanks for your response.

[theoldkid]

Just took a closer look at my idle RPM. It is way down in the 500 to 600 range. No wonder the idiot light blinks!

[Moljinar]

Didn't I suggest turning up the idle in another thread?

[theoldkid]

You sure did.

I just noticed that all I have to do to stop the blinking idiot light at idle is to increase the idle RPM about 100 (to around 900). Is doing this as simple as adjusting the adjusting screw that pushes against the throttle linkage? See picture below.

[tolusina]

Quote, originally posted by theoldkid »

You sure did. I just noticed that all I have to do to stop the blinking idiot light at idle is to increase the idle RPM about 100 (to around 900). Is doing this as simple as adjusting the adjusting screw that pushes against the throttle linkage? See picture below.

NONONO!!!!
That's the absolute wrong place to adjust idle!!
Let's get the stop screw back where it belongs, then adjust idle speed.

Loosen the lock nut, back the screw off until the screw visibly clears the throttle arm and the throttle plate closes completely. The throttle plate is likely to bind in this position, we don't want that, a sticking throttle is miserable to drive, the throttle plate and throttle body will soon wear grooves into each other.
Turn the screw back in until it just makes contact with the throttle arm, turn it just farther enough so the throttle plate doesn't stick in the bore, should be no more than 1/8 of a turn. Tighten the lock nut securely, never mess with it again.
__________
Reach around to the back side of the throttle body, 90° from your pic, on the vertical face, find the 7 mm screw. That's the adjustable idle air bypass, the one with the often mentioned o-ring. If it's real free to turn, take the screw out at the hardware store, carry it in and find a suitable o-ring replacement. Turn the screw in to decrease idle speed, out to increase. Best to unplug the idle boost valve(s) while adjusting for your optimum 850 to 900 rpm.

[theoldkid]

Thanks very much. As usual, you saved my butt!!

[theoldkid]

Follow up on the follow up.

I did as you said. Put the setting for the stop screw back where it belongs and tightened the lock nut.

Then I got out my 7 MM box wrench and adjusted the REAL idle adjustment screw at the rear of the throttle body so that idle speed is now about 900 to 950 RPM. The screw did not feel loose, so I didn't replace the o-ring.

I took the car out on the freeway to get it really warmed up, and then got off the freeway. At every traffic stop the RPM was where it should be (900 to 950), and no more blinking oil pressure light.

Thanks to you and many other great participants in this forum, my problem seems to be solved.

[tolusina]