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04 Trailblazer - Oil Pressure Fluctuating


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a1handy
User

Aug 30, 2020, 1:15 AM

Post #1 of 8 (260 views)
04 Trailblazer - Oil Pressure Fluctuating Sign In

I just purchased an 03 Trailblazer with 134000 miles that had been in a minor front end accident. I have no history on the car. The truck runs great but I noticed the oil indicator goes from normal for the first few minutes after start to zero thereafter. I initially had to add about a quart of oil and when I did so I noticed under the cap was milky but nothing on the stick. The engine coolant level remains steady and the vehicle has not run hot during the time I have had it. There is a slight valve tap but no bottom engine noise at all. Are there any suggestions as to what this might be other than a head or head gasket problelm? Thanks


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Aug 30, 2020, 4:26 AM

Post #2 of 8 (255 views)
Re: 04 Trailblazer - Oil Pressure Fluctuating Sign In

The very first thing to do is find out if the gauge is telling you the truth. You could hook up a manual gauge to monitor the pressure but it would probably be easier to just replace the oil pressure sender. You'd have to remove it to hook up the gauge anyway.

If the pressure turns out to be accurate, then I would suspect junk in the pan plugging up the pickup screen which can be fatal for the engine if not resolved.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Tom Greenleaf
Ultimate Carjunky / Moderator
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Aug 30, 2020, 6:29 AM

Post #3 of 8 (249 views)
Re: 04 Trailblazer - Oil Pressure Fluctuating Sign In

Ditto: Hope this is worth another engine that sure smacks of a wasted lower end (block) will show just those signs if not totally fooled by something else do check as said to prove it. Just got the thing this isn't a fun beginning IMO,


T



a1handy
User

Aug 30, 2020, 11:59 PM

Post #4 of 8 (228 views)
Re: 04 Trailblazer - Oil Pressure Fluctuating Sign In

I have decided to change the oil and filter as well as the sending unit to see what this does if anything. Am I correct in assuming that the engine has a failsafe that would shut the engine down if the oil pressure gets dangerously low. If so this has not happened. I tend to agree that it may be some type of blockage instead of an oil pump failure since it seems to occur after the engine has been operating for some time.


Tom Greenleaf
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Aug 31, 2020, 1:28 AM

Post #5 of 8 (221 views)
Re: 04 Trailblazer - Oil Pressure Fluctuating Sign In

Hmmm on the failsafe? If it was equipped it doesn't work or would rely on it even with one.
Test the pressure with a gauge you screw in where sender is read it live it's out anyway. Rent it ask if locally a place does that or how much you need to know or wasting good $$ on a lost cause.
What and why this is likely: It already wore cam and crank bearing (the strong guess) so gear driven oil pump first fills up those gaps before it can make pressure would be late to put out the warning light (red oil can icon) or gauges don't real pressure instantly.
Despite various viscosities (thickness of oils) it's better right away cold then thins out warmer to hot is leaking out of bearings faster then it can keep up with so it's pressure doesn't make it to other items relying on it quickly. The why is the list - lack of oil changing, a leak and allowed to run low rapid wear happens in seconds possible. It might seem better when filled or have ended then.
Oil also helps cool things and has to return to pan fast enough is where sludge can be holding oil higher it passively returns down milky seen may only be up high or thru engine either fooled by some moisture condensing from air or even minor mixing with coolant.
So lower end hogs initial oil the higher up waits too long both wear. Bearings of lower end would mean a redo of crank and rod bearings is a gamble and patch IMO it's not fixed for long life those things matched when machined new don't even work in another new one that day is the last chance it could last indefinitely from new. That machine work became just that engine once it's still around so was right once lost it with one of the above now what to do?


Yes you can fix anything but it quickly out costs any possible life or the thing or value of whole vehicle vs another totally that never had this problem.
BTT: HT said right away the test is a real gauge is the way to know the issue is real not fooled by something else and you just said no (essentially) just toss that switch for another and see what it does.


It's yours now do what you want but IMO makes more sense to know if a lost cause now and quit the $$ bleed then dump it for parts is about what you bought and didn't know it for sure,


Tom



Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Aug 31, 2020, 4:24 AM

Post #6 of 8 (219 views)
Re: 04 Trailblazer - Oil Pressure Fluctuating Sign In

No, there is no such thing as a "failsafe" shutdown. Stop driving this until you find the problem. You don't get a second chance with no oil pressure.

I agree with changing the oil and the sensor to see if it makes a difference.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



a1handy
User

Sep 6, 2020, 1:51 AM

Post #7 of 8 (165 views)
Re: 04 Trailblazer - Oil Pressure Fluctuating Sign In

I replaced the sending unit, changed the oil, and filter. Unfortunately, the same thing happened. I am going to rent a guage today to make sure the readings are correct but it sounds like I have a pump problem. Obviously it looks like someone has been driving this vehicle like this for a while.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Sep 6, 2020, 3:49 AM

Post #8 of 8 (153 views)
Re: 04 Trailblazer - Oil Pressure Fluctuating Sign In

I doubt it has been going on for too long because it can't survive too long without oil pressure.

There's most likely something in the pan that is clogging up the pickup screen. Dropping the pan is probably the next step.

This appears to be no simple job. If it's a 6 cyl 2WD, it's about 4 1/2 hours. If it's a 6 cyl 4WD, it's closer to 10 hours.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.







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