Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum banner
1 - 20 of 20 Posts

·
Registered
Joined
·
6 Posts
Discussion Starter · #1 ·
I have a Chevy trailblazer 2002 LS

Needing to know at what point after replacing the whole car at 233, miles do we buy another replacement or look fir a motor if its still going ,lol


previous story



I have had my baby for years its a 2002 LS Chevy trailblazer, ive replaced tires, o2 senser , coils, coolent , battery two wheel bearings on the left side, a tie rod also on that side, Alternator, fuel pump, windsheild, and now a ignition switch , it has 233, thousand something lol

so I live in Kentucky and my daughter wanted to go to the beach , headed over to Myrtle Beach which is a 7 hour drive from my location , then after that stop on the way on 95 down another 6 hours to daytona beach , then over west to orlando , stayed a couple nighs drove about thirty miles out of orlando and dead quit on the hwy all gauges, so tow bill to the nearest place was 200 then 160 for a missdiagnoised said it was the computer board, but found a Semi car hauler to haul my vehicle from Clearmont Florida to corbin kentucky another 900.00 in tows and then 60 to the GMC dealer,

400 dollars waiting for the ignition switch , so my question is , was it worth it.. yes , and by the way we rode with the car all the way in the semi lol , who else has done long hauls in older cars


and should i just be looking for Motor at some point . ? and is it safe to do long hauls in the older trailblazers .
 

·
Premium Member
'05 Chevy TB EXT
Joined
·
5,642 Posts
$400.00 ---- for a $40.00 Standard Ignition switch?

You're being hosed --- don't you work on your own car?

If you want to own older vehicles, the least you should do is be able to install parts and diagnose when they go bad.

If you cannot do that --- I'd be buying new cars every 10,000 miles or 6 months --- whichever comes first.
 

·
Premium Member
2004 chevy trailblazer_lt
Joined
·
3,229 Posts
Welcome to the Forum!

Also, there is no need to post the same thing in multiple places on here. Once is enough, even if it is in the wrong place.

Only you can decide when to move on. It comes down to how much is a new (to you at least) vehicle going to cost you per month vs what the current one is costing you per month. Now, some things are going to need to be replaced periodically like tires, wheel hubs, suspension parts, etc. Now if you do decide to keep the TrailBlazer, then I would suggest learning how to maintain your vehicle and sticking around here for guidance, pointers, and some laughs.

Good Luck!
 
  • Like
Reactions: cprodave

·
Premium Member
'05 Chevy TB EXT
Joined
·
5,642 Posts
Welcome to the Forum!

Also, there is no need to post the same thing in multiple places on here. Once is enough, even if it is in the wrong place.

Only you can decide when to move on. It comes down to how much is a new (to you at least) vehicle going to cost you per month vs what the current one is costing you per month. Now, some things are going to need to be replaced periodically like tires, wheel hubs, suspension parts, etc. Now if you do decide to keep the TrailBlazer, then I would suggest learning how to maintain your vehicle and sticking around here for guidance, pointers, and some laughs.

Good Luck!
Awwwwww! You're an old softie!
 

·
Registered
Joined
·
6 Posts
Discussion Starter · #6 ·
$400.00 ---- for a $40.00 Standard Ignition switch?

You're being hosed --- don't you work on your own car?

If you want to own older vehicles, the least you should do is be able to install parts and diagnose when they go bad.

If you cannot do that --- I'd be buying new cars every 10,000 miles or 6 months --- whichever comes first.
Most women never go to school for this one and not worth my time to learn,

thank you
 

·
Premium Member
'05 Chevy TB EXT
Joined
·
5,642 Posts
Most women never go to school for this one and not worth my time to learn,

thank you
Who went to school for this stuff? Chose your words carefully here --- you're on very thin ice ......

Classes and seminars? Sure ---> later once you get a job --- would be necessary for computers and specialties in a mechanical trade ------ but unless one starts in a trade school -- any thoughts that mechanics is a male-only bastion, then that's reverse discrimination and sexist.

So, since you opened this sex-door --- why don't you get a husband or boyfriend to take care of you?

If it's "not worth your time to learn" means you want freebees and that's not what this is all about.

I'll say that asking questions HERE means you want some assistance --- not someone to do it for you.

The helping hand you're looking for is at the end of your own arm.
 

·
Registered
Joined
·
15 Posts
I don't even think it's a man/woman thing. You either have some interest to learn about cars and their workings or you just buy/lease something with a warranty and keep replacing it. Even just understanding what maintenance to do is a big help with keeping a car reliable.

Once you have replaced most of the wear items and are on a good place with maintenance it's usually better to keep what you know rather than buy something unknown, unless it's new with a warranty.

You could get a compression test on the engine. That would help let you know how well the cylinders are working or if they're worn out. Maybe someone can chime in if the oil pressure gauge is a real gauge or a fancy idiot light. Some gages are more on/off indicators and read the same level no matter what. If it's a real gauge then making sure you have good oil pressure is the next thing to look at. You could get someone to hook an actual gauge to it and see.

Have you kept up on transmission and axle maintenance? Fluid changes, etc?
 

·
Premium Member
2004 chevy trailblazer_lt
Joined
·
3,229 Posts
The instrument panel oil pressure gauge is a "fake reading". Let me explain. The 4.2L inline 6 cylinder engine was designed with oil flow rather than oil pressure in mind. So, as long as the flow of oil throughout the engine is adequate or more than adequate, the engine is happy and the ECM is happy and this happiness is sent to the oil pressure gauge on the instrument panel in the form of a higher than actual oil pressure. Why? Because most people have it ingrained into their thinking that a higher oil pressure is better than a lower oil pressure.

So how does one find out the true oil pressure? They install a mechanical oil pressure gauge and measure it. I have read where several people will connect a mechanical oil pressure gauge to the engine someplace near the oil filter. Also, if memory serves me correctly, I believe the normal engine oil pressure is around 12 psi at highway speeds. If I am wrong, someone please correct me.

Now, if your dummy oil pressure gauge on the instrument panel shows a low to almost zero oil pressure, and your engine is not making any noises related to a low oil volume in the engine, then the most likely cause is the oil pressure sending unit (which is down by the oil filter) has gone wonky and should be replaced with a new one from one of the following trusted brands - ACDelco/GM Genuine, Standard Motor Products (non T series), NAPA Echlin, Delphi, or BWD (non P series). Please stay away from off brand, no-name, white box specials with prices so low you won't believe it's a sensor, etc., as they are junk and will likely leak or fail in short order.

Good Luck!
 

·
Premium Member
'05 Chevy TB EXT
Joined
·
5,642 Posts
This could ALSO be a bad stepper motor and there's only one way to test it ... a bi-directional scanner can do it.

With that level of a scanner, you can force all the gauges to go from zero to 100 percent and that'll tell you if one is not responding well --- if at all.
 

·
Registered
Joined
·
15 Posts
I'm assuming 12psi at idle. Then probably the old rule of thumb 10psi per 1000 rpm. The classic SBC 350 was 15 +/- then 10 per 1000.

What I was getting at is worn bearings cause lower than normal oil pressure. On most Ford's the oil pressure gauge is an on off switch. At 6.5psi the gauge goes to the "normal" position and stays there. That was done because people complained the oil pressure was too low.

I'm pretty sure GM uses a real gauge, but not a super accurate one. Still, oil pressure when driving can give you insight into how worn the bearings are. That plus a compression test would give you a good idea of the engine's health.
 

·
Premium Member
2004 chevy trailblazer_lt
Joined
·
3,229 Posts
With the TrailBlazer platform with the 4.2 L inline 6, as I initially stated, the instrument panel oil pressure gauge is a dummy. It displays what the ECM tells it and the ECM is programmed to send a false pressure reading to the gauge. Oil flow, not oil pressure is the key to the 4.2 L engine. Also, the oil pressure sending unit is essentially an on and off switch
 

·
Premium Member
'05 Chevy TB EXT
Joined
·
5,642 Posts
I'm assuming 12psi at idle. Then probably the old rule of thumb 10psi per 1000 rpm. The classic SBC 350 was 15 +/- then 10 per 1000.

What I was getting at is worn bearings cause lower than normal oil pressure. On most Ford's the oil pressure gauge is an on off switch. At 6.5psi the gauge goes to the "normal" position and stays there. That was done because people complained the oil pressure was too low.

I'm pretty sure GM uses a real gauge, but not a super accurate one. Still, oil pressure when driving can give you insight into how worn the bearings are. That plus a compression test would give you a good idea of the engine's health.
I'm pretty sure you're not paying attention ---- this engine doesn't have pressure as you are supposing. It ain't no SBC.
 

·
Registered
Joined
·
15 Posts
I'm pretty sure you're not paying attention ---- this engine doesn't have pressure as you are supposing. It ain't no SBC.
I am paying attention and I disagree with your statement above. It's a mechanical fact that the oil pressure must rise with engine speed or the crank and rods would contact the bearings and bad things would happen. Additionally, the pump is a fixed displacement pump like what's used on the LS engine. Since the galleys are fixed, an increase in speed brings an increase in flow and an increase in pressure.

The Atlas engines have a normal oiling system until you hit the valve train. There are restrictors in the head gasket to limit flow to the top end, but even that isn't new or special. The VVT is unique. That's it.

Oil is picked up from the pan and then goes to a gerotor oil pump, then to the filter, then to the mains, then up through the restrictors to the head and the cams with a fork to the VVT. The oil pressure sensor is in the block before the restrictions. As the bearings wear and clearances open up, pressure goes down. Therefore, with a good gauge it's possible to get an estimate on how worn the bearings are.

If my understanding of the Atlas oiling system is incorrect let me know.
 

·
Premium Member
2004 chevy trailblazer_lt
Joined
·
3,229 Posts
You are correct that there is oil pressure. It is just that unlike the small block 350s of years past, the 4.2 L engine does not develop the same magnitude of oil pressure. No one has said that there is not any oil pressure, nor has anyone said that as RPMs increase the oil pressure in the 4.2 L engine does not see an increase in oil pressure.

What was said is that in this engine, the flow of oil is more important than the oil pressure. Anytime oil flows, there will always be some pressure due to the friction it encounters as it passes through the oil passageways. The oil pressure will just not be as high as in a SB 350 at any given RPM.
 

·
Registered
Joined
·
15 Posts
So we agree.

I never gave specific numbers but rather made an assumption.

Some digging reveals that idle pressure is 12psi, max pressure is limited to 65psi via a relief valve/spring. At 2,500 the pump moves 11 gallons per minute at 65psi, so pressure ramps quickly.
 

·
Premium Member
2004 chevy trailblazer_lt
Joined
·
3,229 Posts
I cannot cite specific numbers as I have never connected a mechanical oil pressure gauge to the engine in my 2004 TB, and I do not recall what the pressures are that I have seen on this forum, but your numbers seem higher than those.
 

·
Registered
2003 gmc envoy_sle
Joined
·
218 Posts
I side with chem_man on this one. Different designs, different results. Stock VW flat 4, around 10psi, all day, pretty much all RPMs. My racing engine . . . 1835cc from 1600, dual Webbers, with racing oil pump, going through a standard PH1A oil filter adapter, with a racing filter, an oil cooler mounted at the front of the car, a three Qt. reservoir in the system, 20 ft. of hose . . . 15 psi. Engine ran competitively for two years with just typical maintenance. Bad gas killed it.

How old is too old? I let you know when I start considering it on my '03 Envoy.
 

·
Registered
Joined
·
15 Posts
VW's have two relieve valves in them. One to bypass the cooler and one at the end of the line so to speak to limit total system pressure. They limit oil pressure to 28psi and there are specs for the springs and relieve valve piston sizes and tensions to target the correct relief pressure. When the engine is cold the oil cooler bypass opens to allow oil to bypass the restrictive cooler and enter the engine for proper oiling. VW's idle around 10 psi and pressure raises with RPM to a max of 28 psi. It's been a minute but I've played with plenty of them. They're also boxer engines and the forces on one side are balanced by the other. If your gauge was accurate then likely the overall design is what allowed it to live. Also, 10psi with a max of 28 is not as bad as 10psi with a design max of 65 say. If the Envoy is in fact designed for a 65 psi max, try running one to WOT under load with 10psi of oil pressure. I will bet money it destroys bearings.

With all positive, fixed displacement pumps pressure will rise with RPM till the relief pressure is achieved. That is an indisputable fact. We can argue over what those numbers are and what I found can certainly be wrong but oil pressure rises with RPM. The passages are fixed in size and only limited by the relief valve. An increase in volume with a fixed passage size will always give a rise in pressure. To change that and run a constant pressure you need a different type of oil pump or a different, active relief system. I've been a mechanic for 30 years and I've had my FAA airframe and powerplant license for 22 years. I'm familiar with MANY types of hydraulic pumps.

The pump on the Atlas engines is neat in that it moves a huge volume of oil. Bearings leak a set amount of oil for a given clearance and as they wear the clearance increases and thus oil pressure goes down. The Atlas however massively overdelivers oil and dumps excess, so it can make up the difference and maintain oil pressure deep into the engines life as it wears. Only at idle would there be a problem but even at 4-5 psi that's enough with no load. With a manual trans and lugging it down you'd hurt something but not with no load.
 

·
Registered
2003 gmc envoy_sle
Joined
·
218 Posts
I did forget to mention that originally one of the relief valves was made inoperable. I'm glad you mentioned that one went to the oil cooler. I didn't build the engine, I have since lost track of the original engine builder. The local person I had rebuild it when I first got the engine made it operable again, and I didn't know which one that was. The system was intended to run at 45 psi. The 15 was enough.

I wasn't a motor guy and still aren't for a VW. So a lot of this came to me by accident and pure luck that it didn't negatively affect the operation of the system. This was almost 40 years ago. I still have the engine and the last two cars I used it in and someday if I get better organized, I was thinking of attempting a repair or rebuild myself.

My part has gotten so off-topic I won't be talking about this stuff anymore.
 
1 - 20 of 20 Posts
Top