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Grumble. Another leak. Grumble. MPG and stuff too.

AJMBLAZER

AJMBLAZER

Better to be lucky than good.
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Replaced the lift pump about a month ago and have been driving The Blazer semi-often since then. No more diesel on the ground under the pump's area.:thumb:

However now I seem to have engine oil all over under the front output of the transfer case. The CV joint right there is COVERED with black oil. Thinking it must be wicking back from somewhere and ending up on it, then dripping off when it's stationary.:doah:

Looks like it needs new main seals and pan gaskets and probably even a pan as it seems to be leaking out around the dipstick tube.:dunno:

Took it on a road trip this weekend. Drove great, no smoke, started/ran/turned off fine. However I believe it was about 212 miles round trip, mostly freeway at 70ish, and I used up slightly over half a tank. Ouch. Same mileage I was getting before the lift pump replacement.

Just bitchin'.:rolleyes:
 
Shouldn't be. That's less than a year old. Have to check though. Thanks!
 
Well, not the CDR valve. That's leak free. In fact the engine looks it's normal slightly grungy self from the top. Wondering about the pan gasket.:doah:
 
Might be the oil pressure sending unit??....my 85 Burb has an oil leak on the drivers side ,it drips onto the exhaust pipe--looks to be oozing out of the head gasket!--I hope it isn't because if it is,I am in no position to fix it...might be the valve cover,even that job is a pain,having to remove the intake and fuel rail lines (which likely will break,being rusty!)..

I read in a friends Chilton's or Motor's Manual that some 6.2's had oil leaks from the heads,there is a "D" shaped passage casted into the head (on the side facing the block) that was prone to leakage,and GM had a brass freeze plug type thing you could buy and press i with loctite to seal it up--I'm hoping thats not what is leaking on my 6.2...that book is the ONLY one I've seen that even mentions that problem,or the "fix"...so long as mine dont lose 5 qts in a short amount of mileage,I'll probably let it leak and keep adding fresh oil--the truck wont mind the free undercoating...but its annoying having oil burning off the exhaust pipe,the smell in nauseating and could start a fire..(I'll be sure to put "fire & theft" on the insurance if I ever get to put it on the road!..:rolleyes:)..
 
Yeah, it makes a large spot but it can't be much oil actually leaking out. Still about full and that was after a long, fast drive each way.
 
AJMBLAZER said:
Well, not the CDR valve. That's leak free. In fact the engine looks it's normal slightly grungy self from the top. Wondering about the pan gasket.:doah:
Click to expand...

Did you take the tuna can off and try to rattle it? It won't leak if its clogged, it'll build up pressure and make everything else leak.
 
No, ought to try that.

I degreased and powerwashed the bottom of it last weekend. Watching for where these leaks are coming from now.
 
When did the poor mileage start? About the time you went up a size in tires? Did you correct the speedo for the change in tire size?
 
Always been poor. Think the best I ever got coming back from Seattle was 15mpgish. Now it hovers around 14 and change.
 
Have you checked the speedo against a GPS yet? If the speedo is off, so is the odometer and your MPG calcs.
 
I had a GPS with me when I picked it up for you.

Interestingly it was dead nuts accurate with the 31's and not the smaller 29's it came from the factory with.

Right now it's 10% on the nose.
 
Your MPG's are not out of line for an auto transmission with larger tires than ideal for your 3.73 gear ratio. You would probably see better mileage if you went back to the 29" stockers since you have OD available, or regeared to 4.56's. But, not enough to pay for the re-gear. At best your K5 should get 16-18 on the highway. I think you are just suffering from an older motor that is underpowered for the gear/tire combo and it has to work harder. By going to the larger tire you have traded power and efficiency down low for highway comfort.

Now if that thing had a 5 speed manual and the lower gears to match the tires (OD to get you up to highway speeds) you could probably start breaking 20 mpg.
 
Not buying it. The diesels want to be higher geared than the gassers. Ratio wise I'm about the same as the guys with 3.08's and 29's who reported well over 20mpg. 3.73's should be great for the 31-33" tires I've run.

Must have been damn slow with the 29's it had stock.

If Big Ugly got 13-14mpg with 4.56's, no OD, a TH400's bad first gear, and super heavy 38" radials then this thing should be getting better mpg than this. Plenty of power, drives nice, and the trans doesn't shift in and out of gear now with the 33's and this combo.
 
My experience with the 6.2L has been similar to that of the 350 V8 gasser. Best mileage when you keep the RPM's down and best power/mileage combo when you have 31's with 3.73 or 33's with 4.10's. The only thing the OD transmission is giving you is a higher top speed, it will not improve your MPG's unless your in the habbit of over reving the motor without it.

The only diesels that do well with tall gears and big tires are the ones with a lot of power. The stock 6.2L will never be in that category.

When I ran 37's with 4.10's on my '83 K20, my mileage went down compared to the original 32's. I also lost any power I had at lower speeds. The only benefit was the better highway speeds, it just took me longer to get up to speed. I believe a turbo might have been able to turn that around. But, the truck didn't last long enough to try that out.

I never trust individual reports on mileage after swapping tires/gears ect. Most don't know how to adjust for the inaccurate speedo/odo from the tire and gear swaps.

Since your mileage has been fairly consistent since you bought the truck, I would suspect it may not have had the timing set correctly after the IP was swapped or they may not have changed out the injectors along with the IP.
 
The best mileage I have ever been able to get out of a 6.2L was my '79 K10 with 285/75R16 tires, 4.10 gears, and an SM465. I was getting 16-17 MPG when I kept it under 60 MPH.
 
Hrmmmm. I've heard of a place near Lexington that actually knows a thing or three about these GM 6.x diesels. Have to see if I can get them to check the timing.


The odd part...that leak has stopped. Trying to figure out when/how I dumped a quart or so down the back of the engine? Everything is full, it's running great, the usual pan and seal leaks are there...but the baseball sized spot I was continuously getting under the front output of the t-case is gone.
Last weekend I hosed it with degreaser everywhere underneath and went to town on it at the coin operated car wash. Since then...nothing. Drove it around several days and nothing but the usual small spots under the engine.
 
Then it was probably residual oil and fuel from before the lift pump was fixed slowly dripping off. Any competent diesel shop should be able to check the timing.
 
Just wondering how that much fuel/oil got all over under it and wasn't making that big spot back there before?

You said competent diesel shop...that's the problem. If I wanted stacks I'd have my pick. Won't tell me I have an Oldsmobile engine under the hood...more rare.
 
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