I was just wondering what your oil pressure reading is on your 4.3 L Blazer? Mine reads 40 PSI cold & 20 PSI hot at idle, It reads 60PSI cold & 45PSI hot @ 1500 RPM.

Also something else I have noticed is a slight knock at cold start up after it has sat several hours. I can't tell if it is a fuel knock, a main bearing, or even a lifter. It goes away withing a second & if you shut it off and let it set 10 minutes it DOESN"T HAPPEN, only after several hours sitting. I hope this engine isn't going on me. I have had enough trouble with it.
Any thoughts from anyone?
Thanks,

 

I have the knock also for a second or so I think its due to the remote filter and normal after it sits for a night. As for the pressures on 5W30 Q-state torque power full syn in the winter I get 60 cold and 40ish hot. In the summer normally my cold is liike 55 and hot 35. 20PSI is still plenty for idle as long as when RPM's go up it goes up I think your fine.

 

I agree, the pressure appears to be within the acceptable range. If you're using 5W30 and have the start-up noise, try 10W30 next oil change and see if that makes a difference.

 

as for the knock, by what you said i would go with a thrown rod bearing. same thing happened to my truck. the reason that it only happens with ur truck sits is because there is no more oil in the engine so it is just metal on metal rattling in the engine. pain in the *** to replace and if not done proper can f**k up the engine.

 

Thanks for the responses. It doesn't sound like a rod knock, if a rod is going it will knock pretty regular. When I changed to oil about a 500 miles ago after changing it there was no knock at all on start up. Has anyone had a knock from the injectors at cold start? I've been told the Vortec is known for a slight knock at start up caused by the injectors. I have had two different mechanics tell me this. The other thing that came up is I have run NAPA oil for years & a mechanic I know just built a Chevy V8 & put in Napa oil and had trouble with a breaking down of the oil (hot). The presure was fine cold but as the engine heated up the pressure would drop. He said the oil was real thin hot. He said he changed it out and went with Valvoline & it cleared up the problem, plus the oil hot was thicker as it should be. 10-30 oil should be 10wt cold, & 30wt hot.
I drained a little out of the engine today to look at it and it is as thin as water hot.
Anyone else have an experience with this? Tomorrow I'm changing the oil to a different brand Mobil 10-40 change the filter & see what happens. This truck has got me gun shy with all the problems I have experienced. I don't want to lose an engine over oil.
Thanks,
Craig

 

I didn't read all the responses so this may have been covered already, bu there is my .02.

10psi per 1000rpm is GM recommended minimum.

If your getting noise upon start up after its cold, what filter do you use? The proper filter has a check valve in it to hold oil in the engine while it is off. Withuot the checkvalve the oil drains back into the pan.

Typically 40psi is normal at idle and it should go up 10 psi per 1000rpms above that, if your losing oil pressure at higher rpm's? I prefer to run a can of Marlevous Marvins Mystery oil through the oil system just before an oil change. I do that for 2 oil changes in a row. The MMM oil is pretty much Kerosene, and it cleans out all the sludge built up in teh engine. I do this once every 100,000 miles. There are other chemicals taht you can use, MMM is the one I use and have been for a long time.

 

I run Wix filters. But that is a thought I hadn't thought about. Are the AC Delco filters at WalMart OK?

Thanks

 

Stay with the Wix, you're not going to find a better oil filter, period. Now let's talk about oil for a minute. Oil does not get thicker as it heats up. If you have any doubts, put some in a pan and pour just a little out, noticing its thickness. Now, heat the oil that's left and pour some out. Is it thicker than before? No, it is thinner, this isbasic chemical physics. The naming of oil with the 'W' in it was done just as a simple way to convey the viscosity properties when multi-weight oil came out. The easiest way to think of it (in the case of a 10W30) is that it is a 30 weight oil that has the cold pumping qualities of a 10 weight oil, not a 10 weight oil when it's cold that changes to a 30 weight when it heats up. Confusing - it can get even more so, but this is the Cliff Notes version.

 

Great info thanks. For some reason in recent times NAPA oil has changed. Tomorrow the oil & filter will be changed I will see what happens after that. I took it to the shop next door. They did the fuel pump. I will keep you posted as to what is found.
Thanks again great info from all.
Craig

 

Yah wix are fine I use AcDelco filters now since yah you definetly dont want FRAM stay away. As for 10-40 oil im not sure I would go to 10-40, but its up to you. I think GM only recommends 10-30 or 5-30. If you are in a really warm place 10-40 might be fine for me even 10-30 wouldn't work for most of the year.