Starting cold engine - oil pressure (VW 1.8t)

[zanzabar]

I've posted many times on this particular project car. Has low overall oil pressure but runs well. Probably because of bearing wear. My question is: how bad is this?

Vids below show hot oil pressure is almost instantaneous when starting after being off for ~5min. The second video shows when cold (~ 60 degrees ambient temp) it takes almost 2 seconds for oil pressure to build - and it's even worse when colder.

http://www.flickr.com/photos/ljayr88/8718354800/

http://www.flickr.com/photos/ljayr88/8718354864/


Sorry for poor quality. The hot oil pressure is 15-20 psi, the cold oil pressure is 75-80 psi.

 

[trooper001]

What oil pressure does the owners/shop manual say it's supposed to read at any given temperature? What viscosity oil are you running? Per your description and lack of some initial information, I'd say things seem "normal."

 

[zanzabar]

Oh, sorry. I'm not worried about the overall oil pressure. It's on the low side, but within spec (barely).

What I'm wondering is the time after starting the engine (2 seconds) for oil pressure to build up. Why does that take so long?

 

[KrisZ]

Originally Posted By: zanzabar
Oh, sorry. I'm not worried about the overall oil pressure. It's on the low side, but within spec (barely).

What I'm wondering is the time after starting the engine (2 seconds) for oil pressure to build up. Why does that take so long?


It goes hand in hand with your barely within spec oil pressure. If it takes so long to build pressure and it is hard to sustain it, I would suspect oil pump.

 

[suspiciousmind]

How's the RPM on the cold start? Most engines run at 1500+ rpm on cold start and the oil pumps up quickly.

If yours happens to run somewhat less, it'll take longer to fill the galleries.

 

[shDK]

It is a verry well known problem with the 1.8 t AEB engine.The reason is that the mesh filter on the oilpump in the sump gets cloggged. Giving low oilpressure and in worst case destroy the engine.

Remove the oilpan and controle the mesh filter. And a good choise would be to change the oilpump while your in there. It.s not difficult.

 

[147_Grain]

I agree!

Replace the oil pump and clean the oil pickup screen before you lose the engine.

 

[zanzabar]

Oil pump and pickup screen have already recently been replaced. You should have seen how bad the oil pressure was before that!

RPM on startup is completely normal (idles at about 1200 rpm for 30 seconds or so on cold start, idles at about 875 rpm when warmed up). Everything else is completely normal and functioning properly. I'm just wondering if there is some kind of stuck check valve or whatever that is letting oil slip past the pump lines or head/block galleys or whatever that is taking longer than it should to fill up thus creating the extra long buildup time on cold start. Or perhaps 2 seconds is completely normal?

Do others with *mechanical oil pressure gauges* see this kind of delay in pressure buildup with cold engines?

 

[147_Grain]

Since you've replace the oil pump and screen, what viscosity, type of oil, and filter are you running?

....and what is the "Z Blend"?

 

[Audios]

Sig says a blend of G oil and HDEO IM guessing a blend of 5/30 and 15/40. I think youre ok with that slight delay, you also need to fill the chain tensioner upon startup so that adds a little time. Do you get the rattling can of marbles sound when cold starting?

 

[TFB1]

On some engines slow building oil pressure is normal, especially when cold(no I dunno about yours, a drawing of the oil system will show the route oil travels)... Could be it isn't that the oil isn't being pumped or not moving, it's just that the pressure port is at the opposite end of the engine from the pump, so all the galleys must refill before it receives pressure...

 

[zanzabar]

What I have in there now is probably pretty close to a 10-40. I definitely hear the chain tensioner make some unhappy noises when it's cold.

Should I look into a pre-oiler?

 

[threeputtpar]

Originally Posted By: zanzabar
What I have in there now is probably pretty close to a 10-40. I definitely hear the chain tensioner make some unhappy noises when it's cold.

Should I look into a pre-oiler?


I ran a mix of G-Oil and Redline in my A6 for an OC, and it didn't sit well with the car. G-Oil is pretty thin right out of the bottle compared to what a VW normally calls for, so I'd suggest running a 502.00 compliant oil and see what the results are. One of them must be on sale at one of the FLAPS this month.

Also, what filter are you running? I think that the oil filter specced for the 1.8t was changed at one point to increase capacity. The Mann W940/25 I think is the new spec.

 

[Thermo1223]

Run the right oil first, a synthetic to combat the small oil capacity and heat from the turbo charger. I'd use Mobil 0w40 myself.

Per the Bentley manual for 1.8t's in Jetta which isn't really all the different mechanically.

3 secs til the light goes out is acceptable. 20 PSI is the pressure switch spec.

The only other think is maybe the relief valve on the oil piston cooling jets sticks open from the former abuse. Causing a delay in initial pressure build when cold at least or IMO the use of a thicker than spec oil.

Originally Posted By: zanzabar
What I have in there now is probably pretty close to a 10-40. I definitely hear the chain tensioner make some unhappy noises when it's cold.

Should I look into a pre-oiler?


I would run synthetic first...see if it quiets the rattle.

 

[zanzabar]

I've used G-Oil alone with great success in my previous 1.8T passat, but with this one I really need the thick stuff to keep it going. I am using the big filters too. It's possible I suppose that if I switch to a 5w40 it could be lighter when cold and flow better than what's in there now. I'll be changing it soon so we'll see.

 

[threeputtpar]

Originally Posted By: zanzabar
I've used G-Oil alone with great success in my previous 1.8T passat, but with this one I really need the thick stuff to keep it going. I am using the big filters too. It's possible I suppose that if I switch to a 5w40 it could be lighter when cold and flow better than what's in there now. I'll be changing it soon so we'll see.


If you do switch to a heavier 5W-40, use one of the HDEOs in that weight (Delo, Rotella T6, M1 TDT). They usually run on the heavier end of the 40 grade, as opposed to say M1 0W-40 being on the lighter end.

 

[zanzabar]

Put in Rotella T6 and noticed no difference.

Another question:
When starting cold, I notice the needle on the mechanical gauge go up to about 75psi and occasionally it will drop sharply but very slightly (like 2-3 psi) and then return to wherever it was before (usually about 75-80psi). After 30 seconds of running the cold engine I can blip the throttle and the increase in oil pressure with RPMs will also cause this sharp quick pressure drop at around 75psi. It is subtle so you have to focus on the gauge, but it's definitely there and happens every time. Is this one of the bypass valves opening? That's the only thing I can think of causing this. But which one would it be, the oil pump bypass or the oil filter bypass?