Hey folks,

First post on here, and I've got a difficult one.

Got the oil and engine air filter changed 2 weeks ago, replaced all the spark plugs, and today I replaced the serp belt.

Went on a drive, car was fine. Turned the car off, came back out 30 minutes later, got most of the way home when the car started running really rough.

Oil pressure and engine temp were all over the board. Got to a place where I could pull over, and the engine stalled. Tons of burn off coming off the rear half of the engine (probably oil, definitely not coolant). The car wouldn't restart unless jumped.

Was able to get it home after a jump, checked the belt (looks absolutely fine, good tension), tightened the battery connections and the belt tensioner (loosened it when I replaced the belt, thought I tightened it all the way... apparently not).

After I did that, it's still running rough, with a significant, continuous knocking sound at about 12-1500 RPM.

I was a diesel mechanic at one point in life, so i know compression engines. I am not 100% solid on combustion engines, so I could use a master's advice.

Thank you all for reading and your assistance in advance.

 

One more thing, when starting the car, seeing quite a bit of black smoke at engine start, and more than normal when accelerating. Know that normally is due to fuel running too rich, not sure if it's part of the problem, or a different one

 

Please specify your Blazer.

Year
Model
With or without A/C

The routing of the serpentine belt is quite important and on some models can be messed up to the point that the water pump rotates into the wrong direction.
Some models do have a sticker in front of the radiator on the upper crossmember in the engine bay showing the routing of the belt.

Nevertheless it sounds as if there is a more serious problem.

You write "Oil pressure and engine temp were all over the board". What do you mean with this?
Was the oil pressure low and the coolant temperature hot? If hot - how hot?

Knocking noises at these rpm can be indicative of a lot of problems.
Starting from top to bottom:
Cylinder heads - Valvetrain: Someting misaligned or someting broken or bent.

Cylinder heads - Exhaus manifold: A blown manifold gasket or a crack

Engine block - Connecting rods: Worn rod bearing on the crankshaft
(bad oil - messes up the hydraulic lifters)

All these will make particular noises but you may have to ask a mechanic.

For troubleshooting I would suggest to start pulling the spark plugs (throug the wheel well with a long wrench) and have a look at those. Keep them in order of the cylinders to be able to identify the cylinders.

https://www.ngksparkplugs.com/about-...d-a-spark-plug

If you can get hold of a compression measuring gauge - and as the spark plugs are all out do a compression test as well and note the results.
(All plugs out - disconnect the ignition coil or ground it with an appropriate ignition testing/grounding cable. Pull the circuit braker of the injection.
At WOT (wide open throttle) have somebody crank the engine while measuring the compression through the spark plug holes.

As a precaution before having diagnoseed or even fixed the problem I would not run it.

Hope this helps - get back and post the problem or even some pics or a vid of the noise via youtube.

Mark

 

Hey Mark,

My apologies, It's a 2002 Blazer LS 4.3L. Has A/C

Update: figured out the knock, one of the tensioner was loose. Tightened it up, and the knock is gone.

In regards to the gauges, oil pressure gauge goes from 25 to 45-50 when accelerating at idle and the temp gauge maxes out. The engine/radiator aren't even that hot... thinking maybe I grounded out a wire somewhere? Dropped a socket down under the battery at one point (or 2) while replacing things. Not sure if there is a temp sensor or something I grounded out in that area... wouldn't really make sense to have one there, but... opinions???

 

Update: Replaced the tensioner and tstat. Engine will run fine for about 15-20 minutes, then the car goes up to ~240° pretty quick and the oil pressure starts going nuts... took a look into the reservoir and radiator, and it unfortunately looks like the previous owner stop leaked it.

Thinking that's causing a blockage in the cooling system. I don't have even close to the funds to replace the radiator/whole cooling system, would just doing a flush take care of it?

If that isn't the issue, any other suggestions that may help my situation???

 

no real way to flush stop leak, need a new rad

 

hmm - try searching the forum for your specific model and about flushing.

What do you mean with "oil pressure goes nuts..." Does it:
- fall and not recover
- fall and recover when upping rpm by a bit (above 1200 - 1500 rpm)
- rise
- ...

There had to be a reason why somebody put's stop leak into the radiator. But could also be bad liquid or other gunk. A flush may be a starting point. Also check oil level and how the oil looks frequently even daily. (To know if coolant leaks into the oil or oil leaks into the coolant)

Temp sensors are normally found on the block or the spider somewhere in the water jacket. Older models had 2 sensors - 1 for the injection and ECU and 1 for the dash indication on the sides of the cylinder heads.
Bad sensor or short could be a cause but normally these sensors are at the end of some cabling on the engine electrical harness and not around the battery.

Can you get a hold on the previous owner? Ask him about that.

Don't know about the 2002's cooling system - I'm a GEN 1 guy.

General experience with that sort of problem:

Is it cold in your place?
And does your blazer have the remote oil cooler/intercooler (oil lines running to the sides of the radiator)
This can very well explain why it takes some 15 - 20 minutes to get hot.

Try to figure if the radiator gets warm in some places - should be warm first on the hose from engine to top of radiator, then down the "IN" hose side and across.

I would definitively try a flush as first measure. (Pls meet the requirements of your place for the safe and correct dealings with the old coolant liquid)
Replace with a good anti-freeze. Wash or clean down in order to see any leakage in the future. (Hoses, Radiator, lower front part of engine and oil pan.)

And then there is still that serpentine belt thing nagging on me - recheck the correct routing for the belt. If it rotates the water pump the wrong way that could explain a lot.

 

newguy

He might get lucky and at least get it back to work partially. Or look for radiator at the junk yard.
Looking at the fluid could also explain a lot.

This might be of interest:
May 2000 Troubleshooting Professional Magazine: Troubleshooting Automotive Overheating

 

your are correct. I had the same issues he`s having and it was a partially clogged rad. Yes check the oil also