# low o.p. when hot. FRESH 1.6 n/a diesel



## jellowsubmarine (Aug 24, 2011)

New motor, profesionally built and balanced, 1500 miles. Bored with new pistons, pump everything. 

The o.p. is high, as should be, until a good heat soak, then drops to almost 0 when hot. Dello 400 10x40 I beleive, changed twice. MkI VDO oil temp/pressure/volt gauge console, new sending units. Anyone experiance a VDO O.E. oil presure gauge tweak when hot? 

The plastic piece that goes around the oil pump pickup did come back in a box of old parts with the new motor?:what: Do kits have new units? Would that even have effect on HOT only o.p.? 

???????????? TIA


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## damac2004 (Jun 18, 2010)

All I can suggest is you better investigate this before running anymore for any length of time. 

Did you notice something not right on gages and then shut it off or something? Did it sound like a belt was starting to screech? 

Stock system has high pressure warning on yours so it should buzz on the high end? 

And if the sensor in the head had real low rated pressure that should have triggered on the dash gage as well? 

Curious about the gages you are talking about. You have one of those consoles like the gti with round gages with the the oil temp and one of them has actual oil pressure? 

to literally have no reading if its all wired up, you could try and cold crank for a bit with wire off pump solenoid so it won't start. if its pumped up it will shoot oil up top. 

the lack of that splash shield alone doesn't mess with oil pressure if its fed with plenty. its like a baffle. i use them in addition to the one piece rubber gasket they sell with windage tray to potentiall help even that much more from scavenging. 

usually you see people mention the valve sticking on pump causing high oil pressures. 

bently does have measurements for used pumps with feelers. 

to have no pressure is pretty extreme though, things could be clogged but first stop can be the vacuum pump. i had it happen once! something crazy happened and it was starved for oil then machined itself into the cover with the rotary style and locked up! my timing belt shrieked and i turned that sucker off! 

i now run electronic gages as backup with alarms from auber instruments on my daily drivers and the triggers you set are hooked up to aircraft alarm


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## jellowsubmarine (Aug 24, 2011)

damac2004 said:


> Stock system has high pressure warning on yours so it should buzz on the high end?
> 
> And if the sensor in the head had real low rated pressure that should have triggered on the dash gage as well?
> 
> ...


 Sorry, I must not have been very clear. I have a GTI gasser console. installed. Swapped the 5 bar o.p. gauge with a 10 bar USED o.e. VDO/new 10bar sending unit. This is why I suspect, as one possibility, an inacurate low o.p. reading when hot. The oil pressure buzzer does not buzz and o.p. seems well within both high & low range, BUT when the engine is fully hot the idle o.p. drops to several pounds. Since there is *no *"low [email protected] low rpm buzzer" I suspect the reading could be effected by a possible gauge malfunction (when hot). I'd like to find a NEW 150lb (not bar) black rimmed VDO gauge replacement. 

You mentioned the vacuum pump, I've read different places where a worn vac. pump can effect the oil pressure. That makes no sense to me except in your case... a hard failure or lockup-yes-. My pump was rebuilt but I wouldn't mind finding a nice rotary unit.


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## damac2004 (Jun 18, 2010)

Where is this sender placed? If its in the flange and reads normal on a cold start and then drops as it gets hot I would be worried. 

I have seen numerous healthy engines with pretty low oil pressure at the head, when oil is clearly splashing about if you were to pop the cover while running  And also jump as throttle is applied as in watering your whole underhood and engine bay  

Also now you are making me wonder about the "buzzer" function with low oil pressure sender in the head and dashes. I could have sworn my 79 german diesel has a buzzer when the low oil pressure warning is every triggered at the head(i forget the value, i think its somewhere less than 10lbs) 

i could have sworn one went off at idle before in my 82 jetta that i junked. 

somebody smarter than me would have to clarify those points since i still don't trust those gages


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## jellowsubmarine (Aug 24, 2011)

damac2004 said:


> Where is this sender placed? If its in the flange and reads normal on a cold start and then drops as it gets hot I would be worried.
> 
> I have seen numerous healthy engines with pretty low oil pressure at the head, when oil is clearly splashing about if you were to pop the cover while running  And also jump as throttle is applied as in watering your whole underhood and engine bay
> 
> ...


 Yes the duel op. s/u is on the head. I think you are onto something about lower o.p. when hot @ the head. I need to relocate the dual s/u to the lower source and check it. The truck has really come together and is where it need to be finally. :thumbup: 

from my research I think your right... 79' or 80' VW did the "dynamic" o.p. thing. It took alittle thought to retain exactly what all that was about. Initially when I had my console/gauges convrsion installed at a local shop they only hooked up the duel s/u for the oil pressure and dash "no pressure" light to the duel sending unit at the head. One way or another didn't have the dynamic oil portion operational I forget what the exact issue was. My wife drove it home and @ 2k the buzzer would go off. Crappy shop work, I guess they just idled the truck. I had to figure it out for them... Since then I found an EXCELLENT VW guy that has been doing all the work on this truck.


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