Oil Pressure drop off

London Bugger · Post by **London Bugger** » Tue Mar 29, 2005 2:39 am

Hi Guys,

I have a 2110cc motor in my bug its run in but i have only done about 15 miles on it, it has a CB oil pump and is full flowed to a remote mounted fram filter. there is a breather system which vents the case and the rocket covers.

Oil pressure is fine at start up and general running its about 30-40psi but when i floor it and give it some stick the oil pressure light comes on and the pressure drops right down to virtually 0psi does anyone know what this could be????

Thanks,
Rob.

Max Welton · Post by **Max Welton** » Tue Mar 29, 2005 7:18 am

Sounds like the oil in the sump is flowing away from the pick-up tube. Are you running just a stock sump plate?

Max

London Bugger · Post by **London Bugger** » Tue Mar 29, 2005 7:31 am

Max Welton wrote:Sounds like the oil in the sump is flowing away from the pick-up tube. Are you running just a stock sump plate?

Max

The sump is a deep sump and the oil drainer plate is stock.

Max Welton · Post by **Max Welton** » Tue Mar 29, 2005 10:25 am

Well, your symptoms are classic for oil starvation at the pickup.

Any chance the pickup tube extension got left off by mistake? Any chance it was installed but can leak (air) at the junction when that part gets uncovered? Is the extension the right length for the sump?

Max

rcb78 · Post by **rcb78** » Tue Mar 29, 2005 7:20 pm

Sure your oil lines are hooked up to the filter correctly? If they're reversed that can happen. --Ryan

Max Welton · Post by **Max Welton** » Tue Mar 29, 2005 7:58 pm

rcb78 wrote:Sure your oil lines are hooked up to the filter correctly? If they're reversed that can happen. --Ryan

OK, that doesn't make sense. He has pressure except when under Gs (acceleration). How does that relate to reversed lines to the filter?

Max

rcb78 · Post by **rcb78** » Tue Mar 29, 2005 8:33 pm

Some filters have a check valve in them so they really only flow one way, AKA anti-flowback valve. Some does get through, just not enough to sustain rpms. Once the engine spins up, centrifugal forces throw the oil out at the rod throws and and have a tendancy to evacuate the system if insufficiant flow is present. So with a severly restricted oil flow, the pressure can drop as rpms rise. That's just a guess based on an observation from a guy I know. He had the same problem, albeit lower pressure to start with. But it dropped if he free revved it. Problem went away when he found his oil lines reversed.
The only time I've ever seen something like that happen is when someone is running severely low on oil. All the oil gets sucked into the system and you start sucking air when you bring up the rpms. I guess I made the assumption that he checked all the obvious stuff first. Sucking air at the pickup tube extension joint won't be that severe. You would just see lower than normal pressures in higher rpm range, not a drop. --Ryan

London Bugger · Post by **London Bugger** » Wed Mar 30, 2005 4:29 am

Ok heres the situation. The engine was prebuilt. I bought it in Longblock form. the sump is a deep sump that i was told when filling up with oil only fill to the lower dipstick mark? I have not checked the oil pickup tube, should it be right there when you take off the sump plate?

I know the Oil fittings are around the correct way to the filter as i did all that myself.

Thanks,
Rob.

Max Welton · Post by **Max Welton** » Wed Mar 30, 2005 6:51 am

Yes, the oil pickup is visible when the sump plate is removed. It is important that the end of the pickup tube be close to the bottom of the sump. The higher up it is, the more easily it can be uncovered due to windage at higher revs or during high-G situations such as hard cornering and acceleration.

When a deep sump is added to the engine an extension to the stock pickup tube is added to keep the intake at the bottom of the (now deeper) sump. Some extensions fit better than others and there are several ways to attach them (welding, brazing, clamping).

You should fill oil to the usual (top) mark on the dipstick. That's probably part of the problem right there.

Max

London Bugger · Post by **London Bugger** » Wed Mar 30, 2005 8:24 am

Max Welton wrote:You should fill oil to the usual (top) mark on the dipstick. That's probably part of the problem right there.

Max

Looks like I have been miss informed! I will top it right up and see if that makes a difference.

Rob.

britegreenVWSB · Post by **britegreenVWSB** » Wed Mar 30, 2005 5:16 pm

If you haven't done so, pull the sump plate and see if the pick-up tube extension is in place. If it isn't then it's just as if you don't have a deep sump. What size sump is it? 2 1/2 quart? 3 1/2 quart?

TG

500LbGorilla · Post by **500LbGorilla** » Wed Mar 30, 2005 8:20 pm

London Bugger wrote:
Max Welton wrote:You should fill oil to the usual (top) mark on the dipstick. That's probably part of the problem right there.

Max
Looks like I have been miss informed! I will top it right up and see if that makes a difference.

Rob.

Nah.. if that fixes it your extension tube is either missing, loose or has fallen off. I run my 2332 with the oil at the lower line to keep from slinging so much, since the crank adds about 7mm to the depth into the sump. Being too close to the oil's surface with the crank will cause a lot of turbulence to grab the oil and sling it toward #3 and #4 side, and that makes it harder for that head to drain its oil. If you have a sump, you can drop to the lower line and be ok. It's not quite a quart, and in my case, it's still 6 quarts of oil, or a little more.