CUCV oil pump acting funny??

[rpellicci21]

Hey guys. I hope everyones enjoying their Saturday. I'm about to jump into something and wanted to run it by you guys first.

About three months ago when I got my '09 road worthy after some driving my oil pressure light would come on when pressing the brakes. Fearful of the infamous idiot lights I went to add in a mechanical gage but the guy at Autozone suggested changing the oil pressure switch. This worked for a while so I ended up not putting in the mechanical gage at that time. But now the problem is back...

What is throwing me off about this is determining whether it is due to a low idle when slowing down or is the power steering pump hydroboost set up actually putting enough demand on the engine due to the brakes being depressed to have a significant effect on the engine and more so the oil pump. However, I have let it coast at a low idle without a problem but as soon as the brake is pressed the light jumps on, give it gas again and the light goes back off. So, is there some other way the brakes could effect the engine other than through the demand of the power steering pump hydroboost set up on the engine that I might be overlooking???

I've done some research on this and what I've come up with is possibly a worn oil pump shaft? It is hard to say though because it is hard to find other instances of this on the internet being the hydroboost set up isn't the most common on other conventional forums. Any help or insight you guys could give me would be very much appreciated. I'm currently at school and heading home next weekend to try to tackle this issue an arsenal of possibilities/solutions would be awesome due to the short window I'll have to work on it. First is to put a mechanical gage in and see if I can get an accurate reading. Any other thoughts though?? Thanks again guys.

 

[Barrman]

My suggestion is to finish what you started to do a few months ago. Put a mechanical gauge on there so you know what is happening.

Once you figure out your oil pressure is ok. You will need to go tracing wires, cleaning the big through the firewall plug behind the fuse panel, cleaning the plug to the back of the gauge cluster and cleaning every light connector on the gauge panel itself.

The Hydroboost does pull on the power steering pump, but it shouldn't be pulling your idle down much at all if any. Do you hear the engine speed changewhne you are on the brakes sitting still?

 

[rpellicci21]

Thanks for the reply. I'm going to put in a gage this weekend. I don't notice the engine dropping much RPM if any when pressing the brakes but then again it is just my ear as I don't have a tac. It is just odd because I can coast without a problem at a just about an idle but as soon as I try pressing the brake the light goes on and doesn't go back off until the I give the engine some RPMs. Given the oil pressure is low would rebuilding the oil pump be the next step? Also I saw people post on here some different oil pressure ranges, but what is normal. I've seen it can drop to around 5 psi all the way to 40-50 psi is normal under normal operating conditions. Would you have any idea what numbers I should be looking for? Thanks Barrman

 

[Barrman]

I will have to look on my M715 which has a 6.2 and a mechanical oil psi gauge. I think I cruise at 45-50 psi and idle around 25-30 psi. The TM for the 6.2 gives what psi should be seen.

I really think you have an electrical problem. But, verify you have oil psi first. Follow the steps in the TM for testing out the light. Ground the wire with the engine off and the key on to see what happens. If it works as the TM says, then try pushing the brake pedal because I think you are going to find the problem behind the dash.

 

[rtk]

If the engine does indeed have low oil pressure , a rebuilt oil pump will probably not fix it . You need to start thinking crankshaft and bearing clearance . I have been rebuilding engines a LONG time ,and I have YET to find a engine complaint of LOP fixed by just a new oil pump . You are losing oil pressure thru excessive clearance of the RODS and MAINS , NOT GOOD , sorry , wish I could offer you some better info , but as was said above , put a mechanical gauge on your CUCV and check it both COLD and HOT , and go from there .

 

[rpellicci21]

Okay thanks for the advice guys I'm going to get that gage installed this weekend and hopefully all is well with just and electrical issue. Thanks again guys!

 

[Barrman]

I drove the M715 today. Cold idle rpm 40-42 psi. Fully warmed up engine idle rpm 35-37. Driving at around 2000 rpm with a warmed up engine was 50-55 psi.

 

[rpellicci21]

Thanks for the numbers. I have everything installed and all is well. Thanks again guys!

 

[engineman2]

So you're monitoring the oil psi with the mechanical gauge and everything is ok? No pressure fluctuations or other strange happenings? Or did you replace the oil pump and everything was well after that? I'm really curious about this issue. Thanks, engineman2

 

[rpellicci21]

Yes I'm getting similar numbers to barrman. Not thinking since I recently changed the oil didn't check oil level and whether I put the mechanical gauge in topped it off and everything was good. After putting some more miles on it I realized I was burning a good amount of oil. Ive checked out the threads on the cdr valve and think this might be the culprit as my air intake manifold has quite a bit of oil residue in it. I just ordered one so should be coming in the mail soon. I'll let you know the out come

 

[Skinny]

Do not jump to any conclusions without verifying oil pressure with a test gauge like it was suggested. Verify correct oil level, viscosity, pressure switch integrity, idle speed, etc before going further. Many non-electronic dashes suffer this problem because the warning lamp comes on at such a low pressure which is very close to idle pressure. Some dash gauges read near if not zero at idle. Believe it or not, newer vehicle gauges simply lie to you for this reason. Verify with a test gauge.

 

[cpf240]

.. Some dash gauges read near if not zero at idle. Believe it or not, newer vehicle gauges simply lie to you for this reason.

This is exactly what I was told was the reason our '94 Ford Explorer used a dummy light switch for the oil pressure gauge. The Ford tech said they got too many complaints from owners that the "oil pressure dropped at stoplights" etc... So they soldered a resistor to the back of the instrument cluster wiring and used a dummy switch so the gauge would always read the same thing. I hate being lied to my by instruments, so I bypassed the resistor and installed a proper oil pressure sender.

 

[rpellicci21]

Do not jump to any conclusions without verifying oil pressure with a test gauge like it was suggested. Verify correct oil level, viscosity, pressure switch integrity, idle speed, etc before going further. Many non-electronic dashes suffer this problem because the warning lamp comes on at such a low pressure which is very close to idle pressure. Some dash gauges read near if not zero at idle. Believe it or not, newer vehicle gauges simply lie to you for this reason. Verify with a test gauge.

Okay thanks for the heads up. I'm going to have to pick up a test gauge. I was thinking that installing a gauge would have been good enough. I guess it's not a bad idea though, to verify what I'm getting on the newly installed gauge is matching the test gauge to make sure the new one is working correctly.

 

[rpellicci21]

So you're monitoring the oil psi with the mechanical gauge and everything is ok? No pressure fluctuations or other strange happenings? Or did you replace the oil pump and everything was well after that? I'm really curious about this issue. Thanks, engineman2

No, I didn't replace the oil pump. Sorry I sort of butchered my other post when replying on my phone. I originally checked the oil level quick and it seemed fine but after driving and checking it again (several dips to double check) it was low. So I added some oil when I put the new gauge in and no more light and the gauge was reading what seems to be correct oil pressure numbers. I was way over thinking it because of how consistent the symptoms were (ie. no light when coasting but light would come on when pressing the brake while coasting) that it had to be something complicated. But I am going to confirm the readings on my newly installed gauge with a test gauge to ensure everything checks out.

That is what brought me to the CDR valve. After the light coming back on and oil pressure slightly lower, putting more oil in seemed to tame it for now (yes it was low). I seem to burning quite a bit of oil. Doing some more browsing on the forums led me to the posts about the CDR valve and how they sometimes fail. After checking my air intake manifold and finding it pretty oily I'm thinking that may have something to do with it. Definitely going to confirm oil pressure though to make sure nothing else is going on there.

I also just wanted to say thanks again to all you guys on here. This place is great, there are many issues I've taken care of by referring to previous posts and threads and what a huge help. I know I don't put in a lot of input on the forums all the time, but I'm still learning and trying to soak up as much information as possible.

-Rob