1.6 TD Oil pressure light and no vacuum at start up (sometimes)

[33B]

Sometimes at start up i get oil pressure light and no vacuum (stiff brake pedal), and if i rev it oil pressure light goes off and i get vacuum (soft brake pedal), after that I have no problems. Can be days or weeks before it happens again. So is the intermediate shaft getting stuck somehow or?

[srgtlord]

Have you checked the seals on the vacuum pump?

[fatmobile]

 Diaphram style vacuum pump?
If so:
Pull it off and see if the gear is wearing into the brass thrust bushing in the bottom of the vacuum pump.

[33B]

It's a new type vac pump with plastic fins.
I have just replaced it a few days ago because one way valve failed, but the problem with oil pressure light didn't change.

[Ohiobenz]

The intermediate shaft is driven off the back of the timing belt by a smooth pulley.
Possibly a) the belt has too much slack or b) there's oil on the belt.
Either way I'd pull the upper timing cover and take a look.

[33B]

Yes sir. I had that same thought process. I checked the belt it is tight also there was some gunk on it cleaned it up. But didn't change a thing.

Now that I'm thinking about it, it takes a few seconds to pull vacuum. Maybe im just being paranoid when the oil light comes up and thinking that vacuum also doesnt work.

So if my problem goes away with just revving the engine a little bit and than I have no problems for a few days can it be that oil pressure sensor is bad.

I looked at the sensor that's on the oil filter housing it's white. And on the back of the head is BLACK? Shouldn't it be blue? Is that the old type?

Also the engine was NA old style mechanical head. Code is idk just a set of numbers and a VW logo and some 3 circles in a triangle. I turboed it, exhaust, intake manifold, valve cover, oil filter housing, oil cooler, oil pan. KKK K24
The car was originally 1.6td but someone in the 90s swapped it for this engine. Wiring is all still there, so the high pressure oil sensor is connected and working

[libbydiesel]

Sounds like completely typical symptoms of a somewhat worn and out-of-spec oil pump that takes a while to prime if it has drained enough to lose its prime.  Without oil, the vane style vac pump will not work.  Because of the loose oil pump clearance, revving it is required to finally get the pump to prime itself.  It then pumps oil to the vac pump and your brake vacuum assist works.  Simple as that. 

[33B]

Thanks for clearing this up for me.
What to look for when buying a used oil pump? Where do I look for play?
Also can i put a bigger gear diameter oil pump (from hydro engine) in my engine ?

[libbydiesel]

I wouldn't bother with a used oil pump.  They are readily available new.  Be sure to get a quality brand. 

The gears of the various pumps are not larger/smaller in diameter.  The gears are taller/shorter.  36mm tall gears are the largest and used with the hydraulic lifter+turbo engines. 

[WeekendMechanic]

Sounds like completely typical symptoms of a somewhat worn and out-of-spec oil pump that takes a while to prime if it has drained enough to lose its prime.  Without oil, the vane style vac pump will not work.  Because of the loose oil pump clearance, revving it is required to finally get the pump to prime itself.  It then pumps oil to the vac pump and your brake vacuum assist works.  Simple as that. 

Interesting....
Mine takes 3 seconds to get vacuum ,would a new oil pump be instant then?

[33B]

Sounds like completely typical symptoms of a somewhat worn and out-of-spec oil pump that takes a while to prime if it has drained enough to lose its prime.  Without oil, the vane style vac pump will not work.  Because of the loose oil pump clearance, revving it is required to finally get the pump to prime itself.  It then pumps oil to the vac pump and your brake vacuum assist works.  Simple as that. 

Interesting....
Mine takes 3 seconds to get vacuum ,would a new oil pump be instant then?

I'll be replacing mine tomorrow. I'll get you the update on that.

[WeekendMechanic]

Excellent!
Cant wait...

[libbydiesel]

With a new pump it is still a good idea to measure the clearance between the top of the gears and the pump lid.  A bit of plastigage works well for that.  The limit is 0.006.  If it is near there, then you can hand lap the pump body to remove material so the lid moves closer to the gears.  That can make a big difference in whether or not the pump loses prime or how long it takes to build pressure.

[33B]

I've intalled a good used oil pump from 1.6td (quantum/passat cy i think) that i have for parts. Definitely an improvement regarding how quickly i get vacuum. It's not instant but maybe after 1 or 2 sec.
The old pump was jamming when spinning by hand. Good thing i replaced it on time.

[fatmobile]

There is a seal inside the gear on the vacuum pump.
 Make sure yours is there.
It seals around the oil pump shaft.