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Chevrolet Oil Leaks


Chevrolet oil leaks are common, but not on my blazer with a trusted 4.3 Liter V-6 engine. Well maybe not trusted, but at least durable. In fact, so far the only problem I had involved the Vortec fuel injector assembly. However, I changed my oil this weekend, and to my surprise when I crawled under, the engine looked soaking wet with engine oil.

I thought to myself, this can’t be happening to me. The first truck I ever bought brand new needs to wear a diaper already? This  2004 Chevrolet Blazer ZR2 only has 19,846 miles on her. I gathered my thoughts and said, maybe it’s not that bad? So, I performed the oil change and dried up the area and then gave her short run.

Chevrolet oil leaks
Chevrolet Oil Leaks

When I crawled back under the oil pan looked wet again. I easily pinpointed the leak located at the front timing cover. The 2004 4.3 L V-6 has a composite timing cover.

This is one of the reasons that Chevrolet oil leaks remain a common issue. However, I was very surprised with the extremely low miles on my blazer that even this weak area was leaking oil.

But if you look at the picture above, you will see that this was no accident. And no, the leak isn’t from the crank shaft sensor assembly. I double checked that area because it’s a possibility for the o-ring on the sensor to leak.

Why Engines Leak Oil

Improper assembly at the plant caused this Chevrolet oil leak. You can clearly see that the industrial-strength RTV starts out with a nice thick bead and then it just completely disappears at the lower side of the timing cover. Me being a auto mechanic that worked at Chevrolet dealers for 20 years have seen this before.

What happened to me is that when they ran to bead of silicone the machine ran out of glue. And they assembled the engine anyway even though it was sure to leak oil. Unfortunately for me my base warranty of three years 36,000 miles was up two full years ago. This leaves me to solve the Chevrolet oil leaks on my own. And this is one ugly job.

How to Fix Chevrolet Oil Leaks

auto repair problems
Auto Repair Problems

It’s difficult to remove the timing cover on any engine. To solve the Blazer oil leaks, I will have to obviously remove the timing cover. To accomplish this, the engine accessory bracket must be removed from the engine.

This means that the power steering pump, alternator and A/C compressor must also be removed. Oh and don’t forget that the water pump must also come off as well.

Since the water pump is five years old, it would sure make sense to replace this at the same time as resealing the timing cover. I hate replacing known good parts, but how much longer will the factory installed water pump from Chevrolet last?

power-steering-leaksAlso, I found that the power steering pump is leaking, power steering fluid from the front shaft seal. So it looks like I will have to replace the power steering pump as well. I bought this blazer, brand-new in 2004 and paid cash for it because I do not believe in car payments.

If I cannot afford it then I do not buy it. That’s how I roll. But I also wanted to have a vehicle that I drive in instead of work on. Since I fix cars all day 6 days a week I did not want to also have to work on my own vehicle.

Unfortunately for me, this did not work out. I really liked this truck until this past weekend. In fact, I put up a car domain page all about my blazer ZR2. You can visit that page (opens in a new window) to see additional pictures and my story of how and why I bought this Chevrolet truck.

22 Replies to “Chevrolet Oil Leaks”

  1. ZR2-Blazer Slayter

    check out If you haven’t done any mods yet, you will get a bunch of ideas, lol.

    I think oil leaks are a common headache we all deal with, oil pan, rear main, intake gaskets, front seal, crank sensor, valve covers and oil lines are all places to check. I’ve done intake gaskets, one of the oil cooler lines, and the rear main seal.

    I’m sure I will have the rest to do sooner then later!

  2. Engine Expert

    Great topic. I have people call in telling me they’re having oil problems each and every day. I will definately be coming back to read more posts. We specialize in engine and transmission repairs and always look for new opinions and topics on engines and transmissions.

  3. Fat Matt

    i have a 1997 chevy 4.3 work truck it has 300,000 miles any way it still runs strong sometimes but sometimes it acts like its not getting enough fire and cuts out sometimes ive put a new dis. cap and rotor button what else should i do?????? any help would be appreaceted

  4. Ben

    I got a 96 blazer leaking oil a little i think i’m just going to let it leak I wish i would have never bought an American vehicle especially one by GM they are going out of business for a reason.

  5. Charles

    Fat Matt, I had a similiar problem recently, turned out to be a clogged cat. I kept getting codes for various misfires.

  6. Patti

    I have a 2004 Monte Carlo SS, it has about 80,000 and my oil pan is corroded so bad the oil is leaking through. The dealer has denied this under the 6 yr 100,000 warranty due to it not being a body part. If I would have had a small rock hit the oil pan, all the oil would have quickly leaked out.

    The service desk agreed this should be covered but sorry……… The replacement oil pan and gasket are 200 bucks, not to mention labor, having to get under the motor mounts to get the bolts, terrible design. This is why this company will not survive. I am an American car fan, next time I will buy Ford!

  7. Corey W

    My 2004 Monte Carlo SS Supercharged .. had a rusted oil pan. So had a new one installed. Now the fun really began. I have since had the oil pan removed and the gasket replaced 4 times and its leaking again. The car has 45,000 on it. So going to get a new oil pan installed again. If it leaks again its going down the road. I have bought GM since I started to drive. But Ford is really looking good at this point. If anyone else has this problem
    please post.

  8. Bill G

    I have a 96 montecarlo with 220,000 kms on it and it leaks so much oil I’m ashamed to park it in gravel. The car runs great but engine needs a diaper. Did I mention that it is for sale.

  9. LouisD

    First of all; STOP! Put down the sharp instruments while I remind you that for 22 years now, FORD MOTOR COMPANY has stood under the slogan ‘QUALITY IS JOB ONE!” During the same period of time GMC has bragged about how good MR GOODWRENCH is at fixing your broken down GMC Vehicle. No what were you thinking when you compared those two slogans at the time of your vehicle purchase decision? See, there is a reason that during the last 44 years nearly 1/2 of ALL vehicles purchased in EUROPE are actually buit by FORD and FORD Affiliates… THEY LAST! Just a reminder that American CAB companies drive FORDs on average over 400,000 miles during the three years they keep them on the road. You may think FORD’s suck and that’s why you bought a Chevy, but the fact is…FORDs last and GMC crap doesn’t. Now that GMC stands for government motors, it can only get worse. Have a nice day!

  10. Phil Z

    Phil Z says: Mark and ANYONE ELSE INTERESTED;;
    I have an S-10 4 x 4 Blazer, 2004 with the 4.3 liter engine. This as well as a 2002 Monte Carlo S.S w/ the 3800 liter engine WILL BE THE LAST American Cars (especially GM) that I will ever purchase. My Blazer has had to have the 4 wheel drive electronics replaced 3 times. I can’t give you exact parts descriptions but there were at least 3 different electronic items, (switches, modules and what ever else) that needed to be replaced. Of course the replacements were done by tried and error. You know, ” if this doesn’t fix it, then we’ll try this” routine.

    Cost me some serious money since it was about 2,000 miles past the 36,000 mile warranty when it happened the first time. I must give GM credit for the last fix since they felt after me paying to repair the “load” they would cover the 3rd try. It has stayed operational for about 11 mos now but when I do go to 4 wheel drive it is delayed for quite a bit before engaging the 4 wheel drive. This only happens after I shift the gear selector around to reverse, drive, neutral and back and forth several times.

    I’m afraid to take it back to the dealer since the last time I was in for an oil change they told me I needed wiper blades, (I had replaced them about 5 mos earlier) and that i HAD 2 SIDE MARKER BULBS OUT “which still worked” AND THAT MY TIRES WERE WORN AND WERE WEARING BADLY AND i NEEDED A ROTATION AND A RE BALANCING. CAN YOU BELIEVE IT ?? I had new tires put on less than 50 miles before they took a look at my vehicle. Some one over there at the GM DEALERSHIP is FULL OF B S. Now I have the same leak you refer to and from a mechanic friend I have told me about your issue with the oil leak and he had told me up front that the leak around the timing gear cover was the culprit.

    Oh, forgot to mention, the driver side door had its bushings wore out and the hole through which they were installed to hold the door on was worn out of round and the door would flop up and down whenever it was opened. The dealer wanted $400.00 to correct it and they tried to scare me into having them repair it by saying that doors on that model Blazer with that particular problem have been know to fall off. What a piece of junk.. I had it repaired by a local body shop. They removed the door, took off the mount and welded the hole in the mount shut and then re-drilled the hole and installed a new bushing and remounted the door. Oh, I forgot, they had to replace the rubber seal around the door as well. It seems that whenever it rained, my wife or I got drenched with the leak around the door.

    The Monte Carlo,, lord knows that has been a curse. I had a 100,000 mile policy which “I PAID FOR ” and within 2,000 miles after passing the 100,000 mile expiration date the car has been breaking down with problem after problem. Is there anyway that a bit of PLANNED OBSOLESCENCE goes with the GM’s ?? IN my mind, GM along with the UNITED Auto Assembly Workers are worthless. I, a ( DYED IN THE WOOL AMERICAN,,, BUY AMERICAN TYPE CONSUMER PERSON ) am now purchasing TWO Japanese Vehicles.
    NUFF SAID !!!

  11. David

    It is amazing, but I have taken a nearly identical picture of my 2002 2WD Blazer with the same 4.3 engine. Identical leak, and even identical in terms of missing silicone at the base. I am much higher in terms of mileage, and have done well until now with no leaks, but now have the exact same problem. Thank you for posting this.

  12. Brooks

    I’ve been doing some research on 4.3 oil leaks and found your website. I also have the same timing cover oil leak on my 2002 4WD S-10, that you encountered on your on the ZR2. Would you mind answering a few detailed questions about this repair? Did you have to drop the oil pan? I noticed that there is a warning stamped on the front of the pan about an alignment procedure needing followed it the pan position is disturbed. Also did the CKP sensor have to be re calibrated?



  13. Chris

    I have a 1996 chevy c-1500 with the 5.7L Vortec V8. from the factory it was perfect. has 145000 miles on it and barely leaked any oil from the timing cover. I changed out the timing chain this weekend and put a new cover on it along with felpro oil pan gasket and now i have a more significant oil leak from the timing cover. pain in my ass

  14. Charles O. Slavens

    I have a 2004 GMC van with 115,000 miles. Yesterday, while driving, I smelled something hot and when I looked at my gauges the oil pressure gauge was peaked at 80. I pulled over, pulled out the dip stick and it was hot and dry. I looked under the vehicle and didn’t see anything significant; ditto the engine compartment. Can you please tell me what could have happened? Thanks

  15. Wade Quick

    Good Blog and posting!
    I have a 2011 Chevrolet Silverado 1500 4.3L V6 wt model, purchased Dec 2011. The oil pan gasket was replaced at 3001 miles in February after an oil leak was discovered during a complimentary vehicle inspection at my dealership. It has been about 3 weeks since the repair and an oil mist appears to be blowing out and forming a dirt /scum collection area from the mismatch/void area back over the transmission casting. Man, I do not want to be fixing another oil leak at the timing cover as well. I have never owned a new vehicle that leaked oil.

  16. laurin800

    Just bought a 2001 blazer w/4.3 motor. 210k on it. The body is remarkably clean underneath, no rust! Only visible rust was the frame, and I wire wheeled it and undercoated it and it seriously looks like a 2 year old blazer! With… you guessed it, a oil leak. We’re talking the farmers invite me over cause I quell the road dust. Anyways, I appreciate all the responses, they gave good insight. It would seem GM is just as bad on our ecology as deep water horizon was!!! If you add the millions of vehicles and figure a gallon of leaked oil in a year, we have a legal mass pollution problem. !!!

  17. T Dittmer

    Is it possible the leak is coming from the CPS? (Not sure what pressure may be behind it, but there is an O-ring.) My ’04 C1500 looks exactly like this picture — making me think maybe the bead looks that way on many units.

  18. lee fle

    I have a 2000 gmc savanna 4.3. Summer of 2014 I paid $2200.00 to have all oil leaks fixed. And now timing chain cover has a 5″ crack on the timing chain cover. Does anyone have a idea on what caused it.

  19. joe

    My front timing area leaks. My oil pan leaks and maybe the rear main too. Not because of the oil pan leaks in the back. Chevy cut corners in to many areas. Certain plants have poor quality control, big time. Why do auto company’s fall short of doing it right the first time. then it just falls on the buyer cars sucks sometimes.

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