Shoptalkforums.com

For Your Air Cooled Pleasure!
It is currently Sat Dec 20, 2014 4:35 am

All times are UTC - 6 hours [ DST ]




Post new topic Reply to topic  [ 20 posts ]  Go to page 1, 2  Next
Author Message
 Post subject: Low oil pressure getting lower
PostPosted: Fri Apr 06, 2012 10:11 pm 
Offline
User avatar

Joined: Wed Jan 22, 2003 3:01 am
Posts: 497
Location: St. Louis, MO
So long story short, ive been putting band-aids on this motor after I built it a few months ago. (1776, full-flowed...) Things like thicker oil, deep sump, and checking the oil pump end play clearance. Anyway, after the deep sump didnt work, i figured its not an oil starvation situation, cause now there is 1.5qts more oil than there was and the oil pressure still creeps down to 0psi when it idles after it is warmed up. It also only gets up to about 20lbs when im cruising about 3k rpm.
So anyway, I have no other choice than to rip this thing down and rebuild it.
I only have about 6000 miles on it, so it really bothers me that i have to do this.
Now for the questions. What should i be looking for on the tear/down rebuild to cause this awful oil pressure?
It has new bearings, and a new shadek 26mm pump. The pump fits in very tight too. I only drilled and tapped the pump as well (the case wasnt tapped, only drilled for full flow).
Anything else i should look for or do while i have this motor apart?


Top
 Profile  
 
 Post subject: Re: Low oil pressure getting lower
PostPosted: Sat Apr 07, 2012 1:43 am 
Offline

Joined: Sat Jul 01, 2006 8:47 pm
Posts: 14932
Location: Mohave Valley AZ.
What parts did you use to rebuild it? look at bearings for sure maybe possible problem in oil passage too. Doesn't sound right for sure. Maybe somebody has a quick fix.


Top
 Profile  
 
 Post subject: Re: Low oil pressure getting lower
PostPosted: Sat Apr 07, 2012 4:01 am 
Offline

Joined: Sat Oct 13, 2001 3:01 am
Posts: 6546
How do you know your gauge is accurate?
Does the oil light come on at a hot idle? If not, you don't have a problem.
If you really like higher numbers, install a 30mm pump.


Top
 Profile  
 
 Post subject: Re: Low oil pressure getting lower
PostPosted: Sat Apr 07, 2012 1:39 pm 
Offline
User avatar

Joined: Sat Aug 19, 2006 2:13 pm
Posts: 900
Location: Way up in northern California!
Get a set of mics and check all your bearing clearances.
Also I always plug the pump and the case when doing a full flow.


Top
 Profile  
 
 Post subject: Re: Low oil pressure getting lower
PostPosted: Sat Apr 07, 2012 11:09 pm 
Offline
User avatar

Joined: Wed Jan 22, 2003 3:01 am
Posts: 497
Location: St. Louis, MO
I didnt get the case tapped and plugged cause the machinist talked me out of it for some dumb reason.
Also, i have the dual pole sender unit with the idiot light and electronic vdo gauge hooked up to it. The idiot light comes on around 8psi. I was ok when it was idling around 5psi but once the oil gets warmed up it drops to 0psi at idle. Its weird cause when its cold and i start it, it goes up to around 60-70 psi at cruising speeds, and will stay at 40psi at idle, but once everything gets up to operating temps, its no bueno.
I guess ill just take it to Brothers Machine shop and see what they say, and if they can check out my crank and case.


Top
 Profile  
 
 Post subject: Re: Low oil pressure getting lower
PostPosted: Sat Apr 07, 2012 11:27 pm 
Offline

Joined: Tue Nov 14, 2006 1:17 am
Posts: 10160
Location: Just north of Seattle
On the electrical sender for the gauge, it the crowned/belled part facing up or down. It should be facing down. With the belled part facing up, if air gets trapped in there your readings could be wrong. As Bruce intimated, use a mechanical one to verify the problem before you pull things apart.

Lee


Top
 Profile  
 
 Post subject: Re: Low oil pressure getting lower
PostPosted: Sun Apr 08, 2012 1:36 am 
Offline
User avatar

Joined: Wed Jan 22, 2003 3:01 am
Posts: 497
Location: St. Louis, MO
How do I go about with the mechanical gauge?
I'm pretty positive I've got no oil pressure because every thing works fine when it's cold, but then goes to hell when it's at opperating temps. I'll check it out though just to rule it out like u said before I tear it all down. And what belled part are u speaking of? The sender unit it round...


Top
 Profile  
 
 Post subject: Re: Low oil pressure getting lower
PostPosted: Sun Apr 08, 2012 1:48 am 
Offline

Joined: Sat Oct 13, 2001 3:01 am
Posts: 6546
kangaboy wrote:
Also, i have the dual pole sender unit with the idiot light and electronic vdo gauge hooked up to it. The idiot light comes on around 8psi. I was ok when it was idling around 5psi but once the oil gets warmed up it drops to 0psi at idle. Its weird cause when its cold and i start it, it goes up to around 60-70 psi at cruising speeds, and will stay at 40psi at idle, but once everything gets up to operating temps, its no bueno.

Your readings are higher than mine.
When I start my engine cold with 5W-30 oil, I can blip the pressure up to 60psi. Once it's warm, it never goes above 30psi. When mine is idling warm, the gauge reads zero. But the light isn't on. Therefore, there is pressure. This means the gauge is NOT accurate near zero, that's all. Don't let it worry you. Mine's got 70k miles on it, with zero pressure (indicated) at idle.


Top
 Profile  
 
 Post subject: Re: Low oil pressure getting lower
PostPosted: Sun Apr 08, 2012 8:46 am 
Offline

Joined: Sat Jan 14, 2012 11:18 am
Posts: 31
was it a brand new case or used one?
i had a similar problem with my old engine. when the engine was hot the red light would come up on idle. But at higher rpms then idle the red light was not on...
when i rebuilt it, i brought it to the machine shop and they bolted the case half together and put a light inside. the case was warped because of previous heat abuse. and with the light inside you could see the light shine between the case halfs... they said it was what caused my red light to come up.

good luck


Top
 Profile  
 
 Post subject: Re: Low oil pressure getting lower
PostPosted: Sun Apr 08, 2012 11:02 am 
Offline

Joined: Tue Nov 14, 2006 1:17 am
Posts: 10160
Location: Just north of Seattle
kangaboy wrote:
How do I go about with the mechanical gauge?
I'm pretty positive I've got no oil pressure because every thing works fine when it's cold, but then goes to hell when it's at opperating temps. I'll check it out though just to rule it out like u said before I tear it all down. And what belled part are u speaking of? The sender unit it round...



http://www.ebay.com/itm/AUTOMETER-ELECT ... 0115425099

This is an electric oil pressure gauge and the “can” shaped piece is what I was talking about. Some senders look like a can, some have a rounded top shaped like a bell. I was told that with the units with the bell/can and the idiot light that the bell/can part should be facing down so it doesn't get air into it which can affect the pressure reading.

As far as the mechanical gauge goes, there are small screw-in ones that a lot of mechanics have but they may be expensive (not as much as an engine rebuild that was not needed. Doing a quick search I came up with this: http://www.harborfreight.com/engine-oil ... 98949.html. Whether you like or trust HF tools, this is just showing you that they are out there) but you can also get one of the inexpensive ones that use a plastic hose and temporarily install it until you can verify whether you have pressure in the system or not (verifying your electronic gauge’s reading). Again, a quick search and you can see the difference in prices out there: http://www.jcwhitney.com/oil-pressure-g ... j1s17.jcwx.

As I understand things, the rule of thumb on a VW engine as long as the oil pressure goes up ~10# per 1000 rpms to a max of 60#s things should be OK… but there is a bottom limit to that too. The idiot light is supposed to come on at 7# give or take a pound of pressure or two; and some take a little longer to read than others do. On my buggy, the gauge read “0” a half mile from camp and the idiot lite didn’t come on until just as I drove into camp. I don’t like the light to flicker on me so I go after things before the light stays on at idle.

You might want to look at your oil relief pistons and bores also to see if there is anything in there that causes the piston to hang up one way or another. A lot of cars have the relief springs in the oil pump themselves or have ones close by to keep the pressure from getting too high. Air cooled VW engines can have either one or two pistons that are accessed from the bottom of the engine. I had a similar problem with oil pressure twice: the first time I lost an engine the second time I pulled one piston and found gunk in there so I cleaned the bore and piston, put the parts back in clean and I haven’t had a problem with that engine since (I also added a sump as it was an off-road engine. Either one of them or both did make a difference).

My opinion on this and it is worth what you paid for it. :)

Lee


Top
 Profile  
 
 Post subject: Re: Low oil pressure getting lower
PostPosted: Sun Apr 08, 2012 4:35 pm 
Offline
Moderator
User avatar

Joined: Wed Nov 14, 2007 5:19 pm
Posts: 2302
Location: Birmingham AL
Hi Kangaboy,

At idle, below 1000 RPM, you are making less than 10psi with hot oil. That's why VW has the oil warning light coming on at about 6 to 7 psi.

If you have worn bearing saddles under the mains (no linebore) or if someone used an oversized main bearing anywhere (it happens), you have internal bleeding.

These guys are advising you to test your hot pressure with a mechanical gauge to compare readings with what you have.

These is one other reason for low oil pressure, and that's a too-hot engine. Not uncommon after a rebuild if something was done wrong. Do you have an oil or head temp gauge? Remember, the simple too-hot test is if you can't touch the dipstick and hold it with your bare fingers, the engine is too hot.

FJC


Last edited by FJCamper on Sun Apr 08, 2012 10:04 pm, edited 1 time in total.

Top
 Profile  
 
 Post subject: Re: Low oil pressure getting lower
PostPosted: Sun Apr 08, 2012 8:24 pm 
Offline
User avatar

Joined: Wed Jan 22, 2003 3:01 am
Posts: 497
Location: St. Louis, MO
OK, the motor runs hot in general. I have a CHT gauge, and it reads about 350 cruising at 3000rpm. And the dipstick is hot to the touch when its up to operating temp. I have EVERY piece of tin in place, and new engine seals in too.
I know the 10psi for 1k rpm rule, and with my engine running around 20psi at 3k rpm, that is what raised the final flag for me, even after the deep sump.
The relief valve idea may be valid. I have had this problem for a while, and actually took both pistons and springs out and made sure they fit and slide up and down freely, but there may have been a few pieces of crap that got stuck in there for what ever reason after the cleaning, and now holding them up.
For some reason i feel that it is the oil pick up tube that has a leak in it from the tube to the case, and is now sucking air. Also it could be that i didn't tap and plug the case, only the oil pump. It could also be a bad batch of Shadek oil pumps that don't have a good seal on them in the case that a lot of people are talking about. It could also be...a few other things i guess.
I can't not believe the oil light/psi readings because they go hand in hand. When the psi gets to around 8 the light kicks on, and it wont go away till i rev it up to 2k rpm and then get about 10psi (when at operating temp). Im about the stick the original oil pressure sender on there and see what happens.
http://www2.cip1.com/ProductDetails.asp ... DO-360-009
this is the sender unit i have, and the notched part that is facing us is the part that i have facing up (on top). I did it that way because that is the way the letters are oriented correctly.


Top
 Profile  
 
 Post subject: Re: Low oil pressure getting lower
PostPosted: Sun Apr 08, 2012 10:16 pm 
Offline
Moderator
User avatar

Joined: Wed Nov 14, 2007 5:19 pm
Posts: 2302
Location: Birmingham AL
Hi Kangaboy,

Sucking air at the oil pickup tube or the oil-out hole in the case (no plug) can cause low hot pressure, but if fully submerged in oil (oil up to dipstick mark) on a level, idling, engine that should not be the main problem.

The engine running too hot is suspect. With all tin in place, and the fan spinning properly (I once saw an overheated engine because the alternator pulley shaft key was missing and the pully was spinning only because of friction), only little to no oil going through the cooler can be the culprit.

You didn't say what kind of cooler you are using.

I know you hate it, but a tear-down is in order before something breaks.

FJC


Top
 Profile  
 
 Post subject: Re: Low oil pressure getting lower
PostPosted: Sun Apr 08, 2012 11:28 pm 
Offline
Moderator
User avatar

Joined: Sat Feb 16, 2002 3:01 am
Posts: 18231
Location: Van Alstyne, Texas
Reasons it might run hot and/or have low hot oil pressure even if the motor internals ARE right:

...early narrow fan belt w/doghouse fan...
Poor seating surface on oil pressure piston or stuck piston,
self clearanced aluminum oil pump cover...
plastic shopping bag stuck in fan...
Early decklid with doghouse fan...
Too much timing,
not enough timing...
lean mixture and effectively retarded cruise timing (double whammy)
... Thick oil and/or big pump causing oil to get VERY hot at cruise RPM by bypassing the cooler due to excessive pressure
(will not be an issue if full flow cooling/not using the factory relief setup)

My VDO gauge sender reads zero at anything under 15 PSI, referenced to several mechanical gauges I tried.
I have never bothered installing the gauge once I discovered how inaccurate it is.
IMHO the only reason to have one of those is to fill a hole in the dash, as it's not accurate enough to call it instrumentation.

like Bruce2 and many old hands, I run an idiot light and don't worry about it, just like I have for ages...
Even idiot light switches go bad.

_________________
Piledrivers extensions of Newtons first law:
A vehicle on jackstands tends to remain that way.
Further:
The longer it stays on jackstands, the more money will be needed to get it back off.


Top
 Profile  
 
 Post subject: Re: Low oil pressure getting lower
PostPosted: Mon Apr 09, 2012 12:24 am 
Offline

Joined: Tue Nov 14, 2006 1:17 am
Posts: 10160
Location: Just north of Seattle
"... For some reason i feel that it is the oil pick up tube that has a leak in it from the tube to the case, and is now sucking air."

This sentence bothers me a lot. The tube extender (at least on mine it did) clamps onto the engine's pickup with a hose clamp. The additional bit of tube is also slit so that the clamp is as tight as possible. My pickup did drop/slide down as I was clamped up it up tight enough before I put the sump on. I have heard that some people put a tack or two at the top of the join to ensure that it stays where it should.

With all you have said I am beginning to think you do need to get inside and see just what you have or don’t have before you end up with not having. Do the easy checks first but don’t wait if things don’t improve when you get though with the easy stuff. If you pull the engine down then you can replace the sump’s mounting studs with bolts so things are all even without the stud backing out problems and any leaks can be stopped in the process.

Things seldom get better by themselves.

Lee


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 20 posts ]  Go to page 1, 2  Next

All times are UTC - 6 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 3 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group