Ok new to site sorry if it sux (forgive my spelling). Got a 2000 Yukon xl 5.3l. Problems started with coolant loss..(head gaskets)...then started throw o2 censor codes after all censors changed...(intake gasket)...then just before I'm ready to start those projects oil pressure drops....at start 20 psi..after a few minutes almost zero...like barely above zero Mark.....ugh...so changed head and intake gaskets dropped pan and cleaned it replaced pick up tube o ring and tore front apart brand new oil pump...starts right up sounds great no funny noises o2 codes gone no stalling. Oil pressure gauge at zero...just came in from replacing sending unit and still zero. Also before that I pulled oil filter off and started for a few seconds to see if at least it was pumping and it sprayed all over like ol faithful....so I know it's pumping...any ideas...like I said it sounds like it should....has 260k
5.3 no oil pressure
- Thread starter M4ur4der
- Start date
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clandr1
Full Access Member
I suppose it is possible your oil gauge stepper motor has failed. Sounds like you've been pretty thorough.
I like to think so but that's why I ask around. Researching interweb there is a screen below pressure switch I didn't k ow about imma look into tonight and try finding a way to clean oil galleys. during the head teardown and pan removal there was a lot of sludge thinking maybe oil passages are gummed up. Also I hear these engines will prime themselves...can anyone confirm this or should I try priming anyway. Honestly I've never had to this on any other engine I've done oil pump /pressure repairs before so new to me. Also before changing switch I unplugged from harness and needle burried all the way to the right and back to left at zero when plugged back in.
Thanks for jumping in clandr1
clandr1
Full Access Member
Sorry man, I'm not that well versed in the innards of the motor since, thankfully, I've never had to worry about it. Hopefully someone with more knowledge will be along with some better advice.
Its all good.....waiting for car god guru...oh Romeo were art thou
SLCHOE
ASE Master Certified + (L1)
First of all, pull the oil pressure sending unit out and put a mechanical oil pressure gauge on it and see if it's really putting out 0 oil pressure. Run it for 5 seconds or so. If no reading on the gauge, shut it down.
Secondly, how long did you drive it with bad head gaskets? Was it a coolant in oil head gasket failure or a coolant to outside the block gasket failure? Or both?
Running the engine with a bad head gasket is a very bad idea as the coolant can dilute the oil and thus replacing what should be oil between the crank/main bearings and crankshaft journals with coolant instead of oil which would cause serious wear to those bearings. As the bearings wear, your oil pressure will decrease.
Secondly, how long did you drive it with bad head gaskets? Was it a coolant in oil head gasket failure or a coolant to outside the block gasket failure? Or both?
Running the engine with a bad head gasket is a very bad idea as the coolant can dilute the oil and thus replacing what should be oil between the crank/main bearings and crankshaft journals with coolant instead of oil which would cause serious wear to those bearings. As the bearings wear, your oil pressure will decrease.
Ok sorry for novel first off.
Picking up manual gauge tomorrow having trouble finding one in my area but planning to travel to find one probably nearest harbor freight... Tried again today....replaced sending unit and could not find the screen under it I read about through different websites. Assuming it was removed by a more shotty shadetree than myself cuz just other things I noticed during teardown indicates to me it was spit and glued together a lot and the amount of oil sludge Inside no way oil was changed enough even with this mileage although I do my best to the book . I read about one guy who did this and can see others doing the same. not something I would do permanantly going to get one soon part store guy had no idea what I was talking about but easy to find online so may order if I don't find one tommorow elsewhere and just wait before back on road IF I have pressure.....anyway Started engine and it jumped around erratically at 20 psi. I gave it a little gas not more than enough to get it at 1500 rpms and would come up some but still jumpy let off and returned to previous then 0 again....shut it off started again few seconds later and same behaviour....then I gave it gas up to 3000 rpms and got up into 40s still jumpy....and then let off and did the same again jumping at 20s and then 0 few seconds later...shut engine off again. So I'm going to test it manually which yes I should have long ago circumstances and what not is why I haven't. If it reads like it should then I believe it's a wiring/ electrical/connection issue or what not if it's reads at all negatively I'm looking for a new engine. But all the while every time I have started it no unsual noises(knocking ticking).
To answer your question. and I'm not trying to sound douchy I understand your concerned and don't want others to follow suit or think it's ok to drive like that cuz your absolutely right. I have always driven gm cars and am used to head gasket issues so as soon as I had a suspicion of the head gasket it was parked. I started with the thermostat because we had heat loss inside and fluids were normal level. Changed it and topped off. Day or so later only small trips around town heat loss again and low fluid but still holding in reservoir though. Read online it has a secondary heater core and takes a lot of fluid so topped off and ran in driveway for a while to warm up just a idle. Fluid was staying normal but heat wasn't great looked for leaks none visible but fluid coming from tailpipe not a lot but enough to tell it was coolant pulled it into garage and been there since. Some orange goopy sludge on valve covers and timing cover I noticed during teardown. So I believe it to be both in and outside of block. I agree/believe bearings are worn if I can't get a reading on manual gauge.
Manual pressure test will tell the tale I believe. thanks for the input sorry I wasn't more specific In the beginning.
Now that I read my original post back In my head sounds like we kept driving it knowing bad gaskets . No not the case o2 issues were kinda all the same time and decided to do all at once since intake comes off anyway for head removal
SLCHOE
ASE Master Certified + (L1)
Worst scenario. Sorry dude.
