I was planning a road trip that turned into an engine swap.
After seven straight days spent crawling around uder the car, I have the new engine transmission etc attached and adjusted. So maiden voyage around the block: this is sweet. A couple of miles later the oil pressure falls to green light at idle. U turn for a mile home at 20 psi, keeping the revs at 2000. Ahem, this is the problem I built the engine for to solve!

Please help. This makes me want British sports cars for their reliability...

Same sender and gauge as previous engine?

Sort of. Yes, but I added a mechanical gauge on a tee at the engine, and it seems to confirm. Both VDO - I used to like their stuff, but that is certainly fading, because I have had failures with their products recently.

What is the mech gage reading when the idiot light is lit? Are you using a type 4 oil pump. Is this the original oil pump?

it sounds like you just built this engine?

if so is this the very first time its ran?
what machine work did you do, and not do

there are a few things to check
brant

Thanks to both. I did build the engine. The first start ups had 30 - 40 psi at idle, driven by a new aluminum 26 mm type 1 pump. I did not machine the case, but did a lot of measuring and straight edging. Well actually I tapped and plugged the oil passages. I was careful lining up the oil pump with the case holes and made a spacer ring to pull it out about 40 thousandths to match better.
I have 1.7 case, and two liter heads. The new p and cs are 2056. CR is set at 8.4. The cam is type 73 with modifications (I am told it has some similarities to a Raby 9550). I am choosing my words carefully her J.R.
The rockers are Porsche elephants feet, and I set chromoly pushrods to length.

Sadly, the electronic and mechanical gauges show 9 psi at idle of 950 rpm.

Engine runs well, but as I expected goes way lean when the throttle opens. The oil has me spooked. All new Mahler bearings and I did a lot of micrometer work. All journals were at least up to new spec, not the wear limits.

Oh, head temp under the plug was at about 290-300 degrees vdo.

it sounds like you did a good job
I built 2 engines with the same problem you are describing
oil pressure was too low for my comfort after 20 minuetes of warm up
things to check are:

1) - did you case line bore?
2) - were the rod big ends rebuilt?
- per the rod question above.... basically is there anywhere that the bearings could be allowing that oil pressure to escape when the tolerances widen from operating temp.
3) - did you change the oil piston relief valves?... some times (although very rare) the pistons can hang in the bore and create a situation where they are not closing and thus are allowing the pressure to relief off when you don't want them to. Also take some bluing compound and put it on the face of the valve. use a dowel rod in the bottom of the same piston and push the piston up into the bore. Check for sealing with the blueing compound at the interface of the piston face and top of the bore. My builder had a motor that didn't make this seal and allowed the bypass of oil pressure.... shrapnel from the previous engine demise had implanted itself into this sealing face of the bore preventing the piston from full closure
4) - did you blue print the new oil pump? what was the measurement of the pump face to the cover plate. Any gaskets in there?
5) - case sealents.... which did you use. how thick... one of my autopsy's showed too thick of a case sealant application that essentially kept the case halves from sealing tight enough to allow the bearing shells to be tight enough to build oil pressure when expanded at full operating temperature...... (essentially like having worn out bearings with too big of a tolerances allowing oil pressure to bleed off after everything warmed up)


There are probably a few more
this is a start
what can you add in response to the above questions?

Sounds like you have to large a clearance in the bearings somewhere.

I did not see anywhere what type of oil you are using?
What viscosity.

I would also suspect the oil pump itself, I like type4 pumps, they seem to last.

rich

Thanks Rich,
I went with mobile 1 15-50. I find it hard to choose between seating the rings and protecting the cam. The type iv oil pump shaft had backed out. I could have fixed it, but decided not too. Opinions seem to vary. Yeah the oil is going somewhere and it could be the bearings, but I triple check everything, and still i do screw up. Still, out of alignment is more likely than out of size for journals and bearings. I used plastigauge where I could.

Thing I don,t quite get is what changed only a few minutes after startup. I know that viscosity and clearance change with heat, but this seems sort of like an all or none sort of deal.

The shadek pump body is notoriously small. I have been living with low oil pressure at idle, I think on account of that for awhile. - it just slides right in, where the stock one you have to loosen case bolts - o-ringing it would be the ticket I guess.

Again, pump.

Also check the relief springs and valves to make sure you did those right...
See the diagram in the manual and pull them out to verify.

I would not run it till you figure this out.
It may be simple, could be the pump...might be something internal.

Those type 1 pumps are mass produced and do have tolerance issues.
No opinion on that, just a fact.

For my money, I would replace that pump ASAP and see what happens.

You are a perfectionist, pull the pump and blueprint it.
It may just be to far out of spec to blueprint properly, and you will know quickly if the pump is suspect by going through that process.


Rich

I don't know much about building engines, but that seems like a good starting point.

I simply cleanedthem to shiny new and put them back. Problemo you think? Engine coming back out?

what are your answers to the above 5 questions?

I have never built an engine, but have been doing a lot of reading. Brant really seems to know these things, and has laid it out in a very logical order. From what I understand you're supposed to build (at least) 10 PSI for every 1000 RPMs, so even though you're on the low side, the engine does have *some* pressure. Though, would it be safe to assume this would probably mean a shortened engine life? Especially once the engine has some miles on it and loses some pressure over it's lifespan?

Brant, #5 is really interesting. I never would have thought of the amount of sealant affecting the clearances. How does one account for that then when the case is align bored and the initial clearances measured for the bearings?

Maybe you should take a minute and read brant's long post. He pretty much asked all the right questions.

Is the dash light hooked to a stock pressure switch?
Did you buy a pump modified for T4 use? Or did you just put it in?
Did you use a gasket between the pump and cover plate?

Drain that oil and put it in your Honda accord. put straight 50 wt Castrol in. if you don't have 20 psi @ idle add 1 more quart. take 2 asprin and call me in the morning

1. No
2. No
3. I cleaned the pistons and bores thoroughly, but used the original parts. Should have looked more closely at mating surfaces.
4. Yes. I lapped the pump body and gears on a granite plate. Not liking how the shradek type I pump lined up with the holes in the case, I fabbed an aluminum gasket at around 40 thou to pull the pump body out. I used permatex #4 I think. Of course I can no longer find it. It brushed on thin. The vw parts web site touted the excessive output of the 26 mm pump, but now I wish I hd gone larger.
5. Same sealer for the case, following the Wilson book.

Excuses: the rod bearings measured round and still showed honing marks. Passed with plastigauge. Same for other bearings except plastigauge less practical.

I am now at the end of my rope with the car. All winter long and all that money on parts and I am right where I started. The bright spot for sure is the help I have gotten here. Thanks.

Isn't Mobile 1 a synthetic oil? They always run thin and lower PSI after warm up.

Good point Mike! Try some Brad Penn 20-50.

before you pull the motor, I think I would go through the oil pressure relief pistons.
used should be fine if there was no scarring on the pistons or bores.

you can unscrew the lower plug and only a little oil will drip out.
clean the bore with some carb cleaner or starting fluid when its done dripping
re-insert the piston and make sure it is smooth in the bore
visually inspect the sealing face with a flash light inside of the bore/case
then get some bluing compound and test the sealing face

if there is any roughness or damage to the sealing face you can also take some valve grinding compound and use the piston to re-machine that face
if it comes to that you will also need to replace the piston
I've done it once by using a dowel rod on the old piston and turning the old piston for 10-15 minutes to re-machine the face back to smooth.

I know this is likely not your problem
but its worth checking since you don't have to pull the motor to do so

I wouldn't break in with synthetic
but that is only for the rings concern
there is no reason synthetic would give you a lower oil pressure

any size of rebuilt oil pump should still give you good pressure
I don't know if your running a front remote cooler, but your pump should be sized plenty big the way you are..

you can tripple check your oil pressure by changing out to a mechanical gauge temporarily.... I did it when I was in your situation only because I really didn't want to rebuild the motor again.... it didn't change anything for my situation but most of the rest of the fixes require tearing the motor out.

you can pull the pump after pulling the motor and at least inspect it carefully before going deeper.

I'm sorry your going through this
there is nothing that feels good about it.
I did it twice...
it took 5 years to self rebuild the motor twice

brant

It is absolutely responsible for lower oil pressure. Scientific fact!

http://www.mobiloil.com/USA-English/MotorO...l_Pressure.aspx

I like that answer.

Chevrolet engineers once measured the pressure at the insert / journal interface where the parts are separated by a film of oil .... it was 5000 psig as I remember and I don't know any automotive pump that produces that.

Conclusion was volume of flow was more important than pressure though 0 pressure would be a great concern. Excessively high pressure pits the bearing shells.

Just an opinion anyway. More coffee!

I could buy the arguement that you might loose a pound or two from synthetic. Probably on a worn out motor with loose tolerances.

I have used up 7 race engines, and hundred of thousands of miles on street motors all with synthetic.

I have seen 250F on air cooled motors and transmissions... I wouldn't run dino oil at that temp. synthetic can actually handle the cooling issues of air cooled motors better
here is a fun article I came across:
interesting oil weight article

you are not going to loose 40psi of oil pressure from switching to synthetic
and a new motor that is working correctly probably won't loose any

sorry I don't buy this argument as a possible problem for this motor.
buy hey all of our advice is free and worth about the same.

The only possible explanation for that result is the pressure was created by the turning parts and simply fed by the oil pump.

If it was an older motor, I would probably say well ten psi per thousand sounds ok. I am trying to Susan what the big change was from the initial startup pressures. I guess heat.

I will have a squint at the relief pistons but right now I have lost two Porsche engines in two weeks. The second one has hundreds of hours of fussing into it too.

I should have done to begin with. Expecting high output and tight clearances I put in plain 30 weight. Then I panicked and switched to the mobile one without thinking. So this whole thing started with getting my 911 ready for a week road trip with the heroic wife. AFTER changing out two plus gallons of mobile one I found broken head studs. Eighty bucks of oil to be driven twenty miles to storage and then recycled. Now thi batch too.

To borrow from the Grateful Dead: the oil weight's not an issue anymore...bcause most of it leaked out from the stupid pushrod tubes!

However, I did pull the oil relief springs to find this:
Click to view attachment
I think that the smaller spring looks pretty wimpy for keeping oil pressures up. As it was I polished it to make sure no edges dug in. The end result was about 15 psi at idle - just over a grand per thousand.

This is what it looked like at startup.
Click to view attachment
Click to view attachment
I practiced with the old engine before I tackled the oil relief valves under the car. Guess what? No second valve! Actually there may be but it if so it is behind a pressed in plug.

So any advice about those pushrod tubes would be grand. They are laeking at the head mostly, but it may be that when I push them into one slot they opens the other. Thanks you experts all!

late cases only have the bigger pressure relief valve.
you can stretch the spring a little bit too... it won't make the spring any stronger, but if its sagging it might hold the valve higher

put the piston back in the bore with your finger or a piece of dowel
check for smooth operation all the way up the bore
look up the bore with a flashlight and visually inspect the sealing face of the case.

I like the stiffer springs in the aftermarket hi-po piston kits

but stock should work too

as for the push rod tubes...
either :
1) you may have nicked the seals during install and just need to replace the pushrod seals

or

2) possibly the retaining spring under the valve cover/rockers is upside down (not in place? or just plain missing?) and not holding the tubes fully down to seal?

b

Thanks Brant!

I think that the heat exchangers will be making a hiatus while I get this worked out. Still haven't figured out MPS mods yet.

The springs for the tubes are in place, but I may well have boogered up (I think this is how Dr Evil says it) the o ring seals by now. They went in and out several times.

That pressure relief vale at the tail end is looking more like a suspect. Wasn't able to get a good look down the bore with heat exchangers in place. I wonder what others think of the substitution or addition of a ball bearing to produce a more reliable stopper at the end of the spring. Found tat on the forums.

One other thing. I have a small numerical n, but it seems like the pressure transforms at some magic temperature (normal cruising) in which these cars reach a critical point. Is it the oil? Most cars don't get that hot. Or is it the case somehow, wg
Here expansion makes things seem less rosy? Any clues. Today was day nine messing wit it. No more for now . Yous kept me sane®.

That engine will never break in with that oil..

You need to see how hot the oil is and see what the oil pressure is and you need actual values from a numerical gauge.

What were your running clearances? Did you mic the big end of the rod torqued up without the bearing in place?

Yeah, I know about the oil. As I said my original plan was plain thirty weight Dino, and I switched to the other as a quick experiment. As pointed out, not bright. But it is out anyway.

I do not have numbers on the Porsche oil temp gauge. It is not in the red even for the early year gauges. The cht says about 340 under the spark plug.

Yes I did measure the big ends and compared to specs in the four books I have. They were within new tolerance. I started with snap gauges and a normal set of mice, then I bought an internal mic. My numbers were similar with both. Autocorrect has its uses, but I used micrometers not rodents for measuring. The honing marks in the big ends were still like new and evenly distributed.

In many places I see posts about the flat air cooled fours needing and generating less oil pressure than their cast iron brethren. I wonder if that is true. I am still a fair deal better than ten psi per thousand rpm, but at a stop light that brings it down close to the vdo senderbidiot light at nine psi.

Was your 9psi at 950 RPM when the oil was HOT?

The stock senders light the oil light at somewhere between 2-6psi as per Haynes.
I am guessing you are using one of the VDO dual senders since you also know what your oil pressure is. Here is what Aircooled.net has to say about the dual senders... (keep in mind that they say this about items that they are selling - basically telling you not to buy them).



Maybe you don't have an issue...?

I was going to say the same thing. I have a VDO sender and the light does come on as well once the engine is warmed up, but no other issues. It's been like that ever since I switched over to the VDO.

Been bugging me all weekend.
You pulled the relief valve, kissed it, put it back in and it helped.

Did you ever do the extensive treatment that Brant suggested to ensure the valve was seating properly?
Sounded like you did not, or just did not answer his question.

Just that little thing you did made a change, so that is why I am asking.

rich

Same problem...new build, low oil pressure.

Added VDO oil pressure with dual sender, oil temp, and CHT gauges and I have to decide do I really have a problem? I've put 600 break-in miles on it using Quaker State Defy 10-40 (has extra zinc...) and plan to switch to Royal Purple HPS after break-in....if I ever get there.

So, question #1, are the gauges accurate?

The oil temp gauge reads 125F unless I'm at highway speed for more than 20 minutes, then it creeps up to 150F. (I have a functioning thermostat). I used the old sender per Pelican Parts. An IR thermometer shows 175F on the sump and 195F on the oil filter after a 25 mile run. So this gauge seems to read low.

The CHT under plug #3 reads 350F and comes up to temp quickly. The IR thermometer reads 200F to 225F as I measure the head thru the spark plug hole in the sheet metal all around the spark plug. So this gauge reads high.

The IR thermometer shows 600F on the header and 75F on the floor so I thinks its pretty accurate.

So that's 2 gauges out of 3 that need to be calibrated. The oil pressure gauge reads 80+ cold but gradually lowers to around 5 PSI @ idle and 20-25 PSI @ 60 mph. If Aircooled is right then this isn't a problem, I just have to get used to the green light. I tried a new spring to no effect and then machined a relief valve spacer to make the piston 32 mm overall length and that MAY have added 1 or 2 PSI. Next I'll put the old sending unit back on and see if the green light comes on. It never came on before I rebuilt the engine.

Of course I'm still worried I screwed up the rebuild as I used the old pump and didn't worry about line boring. My "knowledgeable" resources said I'd be fine. Rods were rebuilt and balanced along with counterweighted crank, fan, flywheel and pressure plate. Sure runs smooth.

Its been good to follow this and the oil leak posts-which is my other problem. I'll update my results when I can get after things next week.

Good luck guys.

Hi Rich and others.
The road trip is happening now in the upper peninsula of Michigan with my wife and her Honda minivan. Thank God I am away from Both work and the garage floor. After much thought I have decided to pull the heat exchangers and lap that valve surface, and also address oil leaks. Then I plan to adjust the MPS for rich lean and get on with life. I will probably be asking for help with the tuning. I have a new diaphragm, an inductance meter, and the write up from pbanders.

I suspect I do not have a ford or Chevy block, and part of my problem is real, but part is also generated by the high (about nine psi) cutoff for the idiot lite on the dual sender.. More experience with the build should help. It is beginning to look like twenty psi at idle will happen for my fresh tr6 engine, but maybe not for the Porsche.

I suspect that when you start using proper oil your issue will go away. It sounds like you are already 1/2 way there by playing with the spring.

You have not confirmed that 9psi at 950 rpm was hot or cold, but I am inferring hot. If so, you are about where you need to be.

Get a good dino oil in 20-50 (Brad Penn green or Joe Gibbs) and see what happens. This could be a really simple fix.

Zach

I've run the VDO dual sender for 20 years and 100K miles
and on multiple engines
have never seen the green light come on
9psi would still worries me at idle.
20psi at idle is better.

I bet a lot of virgin (never been rebuilt) motors are running VDO dual senders... I would love to hear others in that senario chime in.

I'm with Brant.

The one I'm using has about 25 years on it.
My new engine just passed 3500 miles.
I'm at about 25 lbs. at idle.

Did have a leak at the point were the grease gun hose is going into the block. Paranoid about over tightening. So I broke down Teflon taped the threads.
That did it. Now we're dry as a bone. AX'd it on Sunday. Good test.

Ok, that is a good mark to shoot for. My ax season starts in June usually, so no time to lose. Also I will have a chance to do a post mortem on the old engine that woul lose oil pressure on run five or six.