Opel GT Forum banner
1 - 20 of 57 Posts

·
Moderator
Joined
·
184 Posts
Discussion Starter · #1 ·
Took the GT to do the family visits on Easter Sunday. First the oil pressure would drop coming up to a light at idle, once the idiot light came on. Later in the day the problem got worse, the light flickered a few times. Driving home at night was a problem. Oil pressure was diving at anything less that 2K on the tach, had to race the engine at lights just to keep the oil pressure up, but I did get the car home. Oil level is fine by the dipstick.

I see OGTS sells oil pump covers at $35, are advertised to fix "typical low oil pressure problems". Is this what I need? What is the "typical low oil pressure problem" the 1.9L engines have? Why would swapping a cover fix it?

The next step up in fixes was replacing the gears. I haven't gone under the car yet to pull the oil pump. Since I'm on the East Coast it can take a few days to get stuff from OGTS, I'd like to order what I might need to fix this today so I'm set for a weekend repair session.

Anyone care to comment on if the cover alone will fix this problem, or does this sound like the gears need to be replaced. Thanks.
 

·
Super Moderator
Joined
·
9,768 Posts
Jimsky;
The pressure valve is in the cover. there's a ball valve in there that gets worn over the years as well as it sticks. If you have another one from a spare motor, try it first, or just go ahead and order it from Gil. $35 is far cheaper than a engine rebuild.
 

·
Senior Contributor
Joined
·
903 Posts
The pressure regulator, which can be located in either the oil pump cover OR the timing cover only controls the max pressure of the system. It does NOT affect oil pressure at idle. The typical oil pressure issue OGTS is refering to is caused by scoring of the aluminum oil pump cover. Replacing the cover will likely solve the problem.

-Travis
 

·
Premium Member
Joined
·
1,973 Posts
One of the main reasons why oil pressure drops is if the rod bearings wear out and once they wear out a little bit there gets to be some "play" between the crankshaft and the rodbearing, and they become egg shaped or an oblate sphereoid. this will cause a major decrease in the oil pressure. while the oilpan is off go to an auto parts store and ask for some "plastigauge" (its a thin waxy plastic strip that you put between the journal and rod bearing and then torque it, there is a chart on the paper sleeve that it comes in and depending apon how wide the strip is after you torque it, it will tell you the clearance between it the bearing and the crankshaft.) have fun:p
 

·
OPEL-LESS!!!
Joined
·
2,116 Posts
my GT had low oil pressure and knocked just as bad as a diesel.......no kidding. on the pump cover there is a bolt with a one inch head that faces the rear of the car. take this nut out(it will loose a little bit of oil so you'll need a catch pan its only common sense) a spring and a type of valve will come out. the valve might not come out but just be sure you have it aligned when you re-install the spring. stretch the spring or replace it with a stronger spring. this will heighten your oil pressure depending on how much you stretch the spring or how strong of a spring you replace it with. i've dont this to the motor that was in my GT and oil pressure went from idiling at 0-2 pounds of pressure to 18-20. i've changed the motor due to further left over knocks and have done the same thing to this motor and it went from idling at 6 pounds to 14-16. it seems to hold up but obviousely its not the best fix but it will get you by. it would still be better to get a new cover and gears though
 

·
Senior Contributor
Joined
·
903 Posts
I was hoping to not have to write a book on this but...

Early motors: The early motors have an oil pump cover that is nothing more than a piece of aluminum. It has no moving parts. The oil pressure relief valve is located in the timing cover on the passengers side. This relief valve is little more than a ball being supported by a spring. When the oil pressure reaches a certain level the spring compresses and the oil pressure bleeds off around the ball. This ONLY affects the max pressure of the system. Shimming or stretching the spring can NOT affect the pressure at idle unless something is seriously wrong, such as a wrong spring or maybe a chunk of crud that was between the ball and it's seat was displaced during the shimming process.

Late motors: The spring in the timing cover was replaced with a really stiff spring which set the relief pressure so high that it was never activated. Instead they added the relief into the oil pump cover. Its operation is much like the unit in the timing cover. Unless something is seriously wrong, it will NOT affect pressure at idle.

So, if you were to swap an early oil pump cover on to a late motor your oil pressure will sky rocket somewhat above idle. One would need to install the lighter spring in the timing cover to remedy this situation. If you swap a late oil pump cover onto an early motor the relief valve that was set to the lowest pressure would control your max pressure. Keep this in mind when installing new covers.

Hopefully this covers the Opel specific questions. Beyond this, scoring of the oil pump cover, scoring of the walls around the pump gears, main and rod bearing clearances and so on will all affect the pressure of the system...

-Travis
 

·
Super Moderator
Joined
·
6,024 Posts
EXACTLY what Travis said. The main cause of low oil pressure in Opel CIH engines is excessive end clearance between the pump gears and the end cap, caused by the end cap wearing. This allows oil to leak back past the pump gears, reducing the volume of oil pumped into the engine, and hence provides lower oil pressure at a given rpm. Worn pump gears can also cause this, but that usually occurs at a higher mileage than the pump cover. Simply, the aluminum pump cover wears more quickly than the hardened steel gears. I believe I have seen CIH oil pump repair kits, that includes a cover that has a bit less end play clearance, to compensate for slightly worn pump gears.

If the pump is functioning properly, the next most likely culprit is excessive bearing clearances, usually crank or rod bearings, and sometimes cam bearings.

While a weak bypass spring CAN cause the bypass valve to open, it is very uncommon, and would have NO effect at an idle. As Travis correctly points out, the bypass valve only opens at a higher rpm, when the pump puts out more flow than the available clearances can handle at a given oil pressure. So the bypass valve opens.
 

·
Member
Joined
·
648 Posts
Good thread going. Let me add another question to this talk.

What is a good number for oil pressure on the CIH? My new engine, with new gears and cover is running 3-4 bars on the gauge, with 10W-30 to break in with. Bearings are all new and clearances checked. Is this good enough? I plan to switch to a 20W-50 Castrol Sythetic (can't get away from my British car days), after it's broken in. I know this will add a few more psi. I also know that after a point, more pressure really doesn't add any more safety, it's just rough on the seals and gaskets, and uses more HP to drive the pump.

So, how much is enough?

James
 

·
Member
Joined
·
149 Posts
It was suggested to me to resurface the cover face using wet/dry sandpaper on glass. Haven't tried it yet though.

Does anyone know why Opel made the change from the origional design?

Darrin
 

·
OPEL-LESS!!!
Joined
·
2,116 Posts
me and dad were thinking of possably maching the timing chain cover. that way you can make up for wear in the gears, as just machining the cover will not fix it all. good idea, or bad?
 

·
Senior Contributor
Joined
·
903 Posts
You'll likely spend more to properly fixture the timing cover than the cost of the gears. The pump cover needs to be perfectly parallel to the gears which means that you need to get the surface you are machining perfectly square with the tool.

-Travis
 

·
Opeler
Joined
·
17 Posts
Hi!

@jimsky: I would recommend you to put a bigger oil pump with the cover from the diesel oil pump into your GT. Than use 10W60 motor oil from Liqui Moly and you never have any problems with your oil pressure.

@N61WP: But your oil pressure is 3-4 bars, when the enginge is cold, or? How high is it while you're driving? On the gauge there is 1,5 bar enough, when the engine is warm.
The lamp on the oil pressuren instrument appears, when the oil pressure is under 0,25 bar.

Bastian
 

·
Registered
Joined
·
25 Posts
Oil pump cover

So I've got a new oil pump cover and gasket coming from
OGTS. However I don't have a manual. How difficult a job
is it to replace the oil pump cover?
Any words of wisdom appreciated.
 

·
Registered
Joined
·
112 Posts
Replacing the oil pump cover is one of the easiest fixes I've done to my GT. It's not hard to get to (at the bottom of the distributor shaft) from under the car. Good room there to work with wrenches. You'll have no problems.
 

·
OPEL-LESS!!!
Joined
·
2,116 Posts
my best friend was a shallowwell quarter inch drive socket and a mini-breaker bar to get the pump cover off. its no big deal to do at all as oldroadiedog had stated. just be carefull of the gears falling out when you take the cover off because they can splash in the oil and make a mess, or even put a baby scratch on your arm....be carefull those scratches are deadyl ;)
 

·
Member
Joined
·
240 Posts
I replaced the pump cover on my 73 GT. The old cover was not scored too badly but I think the pressure relief valve was leaking.

Now I went to pull the plug to prime it and the plug is frozen.
I have removed the radiator and front pulley to gain better access and still can't get it to move.

I did read this thread...

Will removing the distributor and turning the pump get the oil flowing. I did not pack the pump with grease but did use engine assembly lube.

Garry
 

·
Member
Joined
·
247 Posts
Garry, are you talking about the plug on the oil pump cover? If it has not been too long since the eng has been run I have had good results by pulling the coil wire to prevent starting, then cranking the motor untill the guage shows pressure. And if you pull the Distb. you can access the oil pump driven gear. You will need a way to spin the shaft. I have made a tool from an old screwdriver that fits into a 3/8 drill.

DAN
 

·
Member
Joined
·
102 Posts
I am planning on doing the same ...

Garry,

Is this a must ? :confused:

garrymc said:

I have removed the radiator and front pulley to gain better access and still can't get it to move.
Garry
I'm plannning on replacing the oil pump cover and just wanted to be prepared as to what I'm going into.

BTW, I hope my plug is not frozen! ... Good luck and keep us posted on the outcome.
 
1 - 20 of 57 Posts
Top