Oil pump or HG? (1 Viewer)

[DR71]

U joints and radiator installed, engine was flushed and the truck runs great, but oil pressure is fluctuating from very low to normal with the throttle. No oil in the coolant or any other signs of a blown HG, no burning smell and no leaks. Hoping its just the oil pump which should have been replaced when we changed the gasket. This didn't start happening until the oil pump gasket was changed. Any ideas would as always be appreciated.

 

[baldilocks]

It is very unlikely that your oil pump needs replacement. The most likely problem is human error; the crankshaft bolt was not properly torqued to 304 lb/ft.

 

[Jason hansen]

X2 on the crankshaft bolt. Mine does the same thing after a hg job and new oil pump seal. I don't know if it's the gauge or low oil pressure. This is a common problem and there is a lot of info on mud about low oil pressure on an 80 if you do some searching.

 

[DR71]

It is very unlikely that your oil pump needs replacement. The most likely problem is human error; the crankshaft bolt was not properly torqued to 304 lb/ft.

Will check that now. Thanks

 

[DR71]

Compression test shows all cylinders within 10 PSI of each other so no HG issues and my buddy swears the crankshaft bolt is tight enough. Is the sending unit a possible culprit?

 

[GeoRoss]

I'd say the next step is to put an oil pressure gauge on and verify the fluctuations.

 

[Tools R Us]

... oil pressure is fluctuating from very low to normal with the throttle. ...

It's normal for the oil pressure to be lower at idle. Was the oil changed, what viscosity is in it?

 

[Jason hansen]

I would be interested to see what the pressure is, I read some where that spec is 3 1/2 psi at idle. I would have to check my fsm. Also I used a torque multiplier to check the crank bolt.

 

[Kaninja]

My oil pressure fluctuates. More so with the stock Toyota filter than the no-name filter that was on it when I received my 80.

 

[DR71]

It's normal for the oil pressure to be lower at idle. Was the oil changed, what viscosity is in it?

5W30 just changed it a few days ago when we replaced the main front seal and oil pump seal. The oil pump looked good so we left it in. As of this morning compression is good from a mechanical gauge. Does this mean its not the oil pump or that its probaly the sending unit? Oil pumps are $300!

 

[Tools R Us]

I have never seen a bad oil pump in one of these things, even in blown motors. It's in the front cover, so very invasive to replace. With that oil, I would expect the gauge to read at the bottom at idle and maybe half way at full song, normal. What was in it before? Many step up to Xw-40, I run 15w-50, idles at the second mark and the third mark at full song.

 

[DR71]

I have never seen a bad oil pump in one of these things, even in blown motors. It's in the front cover, so very invasive to replace. With that oil, I would expect the gauge to read at the bottom at idle and maybe half way at full song, normal. What was in it before? Many step up to Xw-40, I run 15w-50, idles at the second mark and the third mark at full song.

So if the compression tests were okay its a non-issue? The gauge drops to half way between the bottom and 1st hash once its warm. As long as I give it gas it goes in the normal range

 

[Tools R Us]

That sounds normal for 5w-30.

 

[DR71]

That sounds normal for 5w-30.

Thanks a lot. I really appreciate your help and everyone else's. I'll try heavier oil tonight.

 

[baldilocks]

Are you sure that bolt is torqued to 304 lb/ft??? How does the power steering work? Week PS would also indicate an inadequately torqued crank bolt.

I replaced my sender last year and the gauge read low like you describe. I got another sender and it read higher but not as high as the old, leaky one did. So, I decided to get an oil pressure test gauge and my pressure was 20 at warm idle with 15w-40. FSM calls for like 7psi at idle. Rule of thumb = 10psi for every 1000 rpm.

 

[DR71]

Are you sure that bolt is torqued to 304 lb/ft??? How does the power steering work? Week PS would also indicate an inadequately torqued crank bolt.

I replaced my sender last year and the gauge read low like you describe. I got another sender and it read higher but not as high as the old, leaky one did. So, I decided to get an oil pressure test gauge and my pressure was 20 at warm idle with 15w-40. FSM calls for like 7psi at idle. Rule of thumb = 10psi for every 1000 rpm.

The torque on the bolt is correct. The power steering is fine and I did replace the ps pump when we replaced the front seal and oil pump seal last week (oil pump seemed fine and was clean). I'm inclined to try the heavier oil. Thats cheaper than a $%#@ oil pump

 

[DR71]

Are you sure that bolt is torqued to 304 lb/ft??? How does the power steering work? Week PS would also indicate an inadequately torqued crank bolt.

I replaced my sender last year and the gauge read low like you describe. I got another sender and it read higher but not as high as the old, leaky one did. So, I decided to get an oil pressure test gauge and my pressure was 20 at warm idle with 15w-40. FSM calls for like 7psi at idle. Rule of thumb = 10psi for every 1000 rpm.

This all started when we changed the seals and the oil. Dont know what was in it before. Only had it for 3 weeks.

 

[Tools R Us]

Likely had thicker oil, what you are explaining should be fine, especially in the winter.

 

[DR71]

Changing the oil now. Would rather do that to verify its an oil weight issue. If so base lining is finally finished and will get tires under it tomorrow. Will certainly post the results from the oil change.

 

[baldilocks]

An oil pressure test gauge is a cheap tool that will verify all is ok so you don't lose any sleep over it.