Loose oil presure

Sweetmarie66 · May 4, 2018

Hey everyone!!! Ok I really need your help. So just got our 66 coupe on the road again. When we were driving at hwy speed lost oil pressure. Shut it down checked oil . Good. Fired back up oil pressure is back 45 at 900 rpm idle. Ok weird. So we drove off the hwy and drove around the city for 2 hrs no problems. Then today out on hwy went to pass a vehicle, down shifted brought her up to 3800 passed the car went into overdrive and then exited the hwy. bam! No oil pressure! Checked oil again . Good. Fired back up no problems again for a day and a half. Rbohm u out there. Rusty? Anyone ? Beyond frustrated. Oh and yes it has a good quality autometer mechanical gauge. And yes it starts to tick when this happens. Grrrrrrrrr

horse sence · May 4, 2018

Did you have the oil pan off ,or a dent in the oil pan , the suction tube may not have enough space between it and the pan and either sucks up to the pan ,or just cant suck enough oil . Suction tube may be pluging from somthing inside the bottom of the pan such as silicone

Sweetmarie66 · May 4, 2018

Yes I had the pan off when I had to retrieve that dam washer I told you all about. Didn't dent the bottom of the pan. I did use a little rtv on the pan then the gasket. Didn't think I used much at all. The pickup tube looked good. I made sure everything was hospital clean before I put the pan back on as well

horse sence · May 4, 2018

Did you have the suction tube off of the oil pump ? Is it possible it is loose ?

Sweetmarie66 · May 4, 2018

I didn't touch anything. Just wiped clean was pretty clean to begin with.

WORTH · May 5, 2018

Well you have 2 choices, either drop the pan and see if there is an issue with the pickup, or install a mechanical pump to make sure you are actually loosing pressure.

horse sence · May 5, 2018

It sounds like it is starving for oil at higher RPMs ,if all that was done was dropping the pan ,somthing had to happen there ,such as bending the suction tube so it is to close to the pan or the pan or bent up out of the oil reserve. Or may be the bottom of the pan pushed up so it is to close to the pan ,or somthing getting sucked up to the bottom of the suction tube .

rbohm · May 5, 2018

as i noted in my conversation with you, i think you have a drain back issue. at higher rpms a lot of oil gets pumped up to the top of the engine, and if it cant drain back properly, you will ultimately run the pan dry.

Sweetmarie66 · May 6, 2018

Will start the process of elimination tomorrow thanks guys

tos · May 7, 2018

Horse and rbohm are both onto something here. I also think you are starving for oil and something is not able to keep up with that higher rpm. I would pull a valve cover and see what kind of drainage issues you may have. Check the drain ports in the head to see if they are all gunked up maybe even put a quart of engine solvent in and run it to clean everything up? Drain the pan and see what comes out. If that doesn't work you'll have to pull that pan for sure.

Sweetmarie66 · May 7, 2018

What is engine solvent. Does engine flush do the same thing?

I only know what I know · May 7, 2018

Some further thoughts beyond what has already been suggested.

The first thing that came to mind after reading your message was your PCV valve.

Since you pulled the pan recently is there any chance something isn't right with your windage tray?

You might like to these sites out:

http://www.enginelabs.com/engine-tech/engine/tech-crankcase-pressure-control-oil-and-air-control/

http://nutterracingengines.com/racing_oil_pumps/crankcase_vacuum_facts.html

https://www.highpowermedia.com/blog/3733/oil-aeration

This stuff is usually discussed around racing engines but it's just as important for any engine.

rbohm · May 8, 2018

Sweetmarie66 said:
What is engine solvent. Does engine flush do the same thing?

unless your engine is really gummed up with sludge, i would not use a solvent or flush, they are very aggressive. i would instead use some marvel mystery oil instead, it is less aggressive, and also lubricates rather like ATF does, yes its that thin.

as to the others, he has noted to me in a private message that he changed the oil and filter, and the issue seems to have gone away, at least for the moment. i suspect the oil filter he used might have an issue somewhere.

tos · May 8, 2018

Yes engine flush is what I meant (bad choice of wording) and they are safe to use. They are meant to run in your engine for a short period (say 30 minutes or so according to direction). then you drain the gunk out and change oil and filter. Marvel mystery oil is good for say stuck lifters or stuck rings but take time to work especially if the engine is really sludged up. I see you changed the filter and it possibly took care of the problem? That would make since if the filter is gunned up then the pump can't keep up at higher rpms.

Sweetmarie66 · May 8, 2018

When I pulled the pan when I was doing all the work to her it was spotlessly clean. I have always changed the oil once a month regardless of how many hours are on it. This engine since it's rebuild when we bout the car has roughly 3000 km on it. As for the bondage tray I would suspect it's fine as the only thing I did was drop the pan, clean thoughroly and tap the gasket holes flat. Since changing the oil and filter and the PCV valve have not come across again. Although I'm skeptical. Going to pull the VC and run it to see if I can watch the oil drain back. Also a fella had said that my oil pump is shot as I have 45 pounds of pressure at idle 900 rpm. Yet my manual says should have 35 to 50 at 4400 rpm were at that rpm I have a steady 50. Manual says I'm running the required pressure Correct?

tos · May 8, 2018

What does your pressure run at idle? so far your pressures look ok to me especially on an older engine.
if your pan was clean then I doubt you have a gunked up engine unless someone cleaned the pan prior to you owning it?
Did you rebuild it or someone else?
Maybe you just had a bad filter?

Sweetmarie66 · May 8, 2018

No it was rebuilt by reliable engine. Oil pressure is 45 at 900 idle

rbohm · May 8, 2018

the rule of thumb when it comes to oil pressure is 15 psi minimum, and ten psi per thousand rpm when warmed up. which means at least 20psi at 2000 rpm, 40 psi at 4000rpm, etc. one thing i thought of is the oil pressure bypass valve. if the spring is weak then when the rpms climb, its possible that that the pressure relief valve is opening at higher rpms and killing your oil pressure. just thought, but right now i kind of doubt it is an issue.

tos · May 8, 2018

Yeah, I don't know who told you your pump was bad but if its 45 at idle that's right on the money. If your issue is still there and your new filter didn't fix it then I'm going back to a drain back issue. Sound like there is no gunk in your engine so I'm going to suggest when you take you VC off then pour some oil in the head and see if it drains well. If possible look down the drain passages to make sure there are no blockages in the passages. Its a stretch but the oil passage in your head gasket could be too small and not allowing proper draining.

One other thought. Did the builder possibly use a high volume pump? This could pump oil faster than it can drainback at higher rpms.

I only know what I know · May 8, 2018

What engine are you running? I know you said the car is a 66, but any chance you dropped in a 351C which was known for low pressure?

Loose oil presure

Sweetmarie66

Member

horse sence

Sweetmarie66

Member

horse sence

Sweetmarie66

Member

WORTH

horse sence

rbohm

Sweetmarie66

Member

tos

Sweetmarie66

Member

I only know what I know

Member

rbohm

tos

Sweetmarie66

Member

tos

Sweetmarie66

Member

rbohm

tos

I only know what I know

Member

Similar threads

Loose oil presure

Member

Member

Member

Member

Member

Member

Member

Member

Member

Similar threads

Privacy & Transparency

Privacy & Transparency