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Evaluating A Potential Addition To Your Stable of Diesel Rides

Missy Good Wench

Wild Blonde from Cloud Mt
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Location
Newberg Oregon
Here is how I evaluate one of these beasts.

First (After hood is open)
Check coolant level, oil level etc.
Look under the rig for signs of major leaks of oil coolant fuel etc.

Spin the engine without allowing the glow plugs to heat. The starter sound should be even with an even za za za za za za za za za sound

An uneven sound of za za za zzzzzzzzzz za za za is an indicator of a low hole.

Once you have heard this sound you wull never forget it.

If you wonder what it sounds like, remove one glow plug from your diesel (H Front is easy )

Unhook the power to the OP or unplug the PMD and then spin the engine. aside from the swoosh of air from the glow plug you will right quick notice the different sound that things make.

OK

If the thing spins evenly, go for a glow cycle and see how it starts.

Good clean crisp start with no great amount of smoke is a good indicator that things are good in the injection system (compression too)

Some missing and white to bluish smoke that clears reasonably quick could indicate some glow plugs not working.

A longer time with missing and smoke can indicate that the injectors are tired and in need of replacement.

Once the engine has run for about 30 seconds there should not be any smoke at all.
Smoke at this point is indicative of issues with injectors or several other things.

A smooth running engine that still exhibits smoke at idle likely needs a set of injectors.

OK
Its running and seems smooth enough and has no smoke.

Look at the oil pressure.

45 or so is normal for a factory setup 6.2/6.5 and will drop off some when things warm up.

40 PSI runnin at speed and Idle at 20 or so.

While the beast is warming up feel the upper radiator hose, it should remain flacid (Soft and squishy) while the engine warms up.

A quick pressurizing of the cooling system followed by coolant puking over the overflow is an idicator of a blown head gasket, cracked head, cracked cylinder wall or ??? that allows compression into the cooling system.

OK
Engine warming up nicely and no issues. Take the rig for a romp and bring the engine to full operating temperature.

The top Radiator hose should have some pressure but not HARD and no coolant puking from the tank vent.

Engine should idle smooth and even with a nice even diesel cackle to it.

Take note of oil pressure, it should be steady and not below 20 PSI at Hot idle.

Shut down and let sit a couple minutes. Yank the dip stick and look at the oil, it will likely be black. Notice the level on the stick as well as the texture of the oil.

We are looking for signs of Glycol in the coolant.

A diesel will not always show a milky sludge if it is contaminated. The black soot will cover this up very good at times.

If we are dealing with a turboed engine, remove the air inlet to the turbo and inspect the inlet to the turbo.

Some oil pullover is normal as these engines get lots of miles on them. The turbo can even have a fair amount of sloppy residue just as long as its not dripping and totally juicey with oil.

While theair inlet is off, (Engine shut down) spin the turbo impeller, it should spin freely and not show signs of having been rubbing the housing.

Some slight radial play is normal but the shaft should not move in and out that you can feel much.

Look for signs of oil leakage from the turbo cartridge (center section) that is leaking down on the outside.

Some seepage is normal on any engine with a Buttload of miles.

Now lets look under the rig.

Any large drips that emanate from the bellhousing drain hole or around the filter area.

Again some seepage is very normal with miles and time.

Now

How is the tail pipe when your running down the road, smoking any at cruise speed. A little puff of black under full pedal is normal and depending on how the Pump is set up (DB2) or chipped (DS4) the smoke can be more or less.

The engine should run down the road with plenty of power (tain't no top fueler though)
The engine noise should be a nice even cackle that deminishes some with full throttle and gets a bit sharper under light throttle cruise.

With engine hot, shut down and let sit and heat soak for 15-20 minutes.
Try a restart without allowing the glow cycle to finish. The engine should start right up with very little cranking.

A long crank time hot can indicate a worn out injection pump (Was seen on some late DB2 pumps with high miles)


So now lets look at the accessories up top. Is there any undo noise, rattles or other obnoxious noises coming from the water pump, vacuum pump (later 6.5 stuff)

Take note of the belt drive, the isolator pulley (Serp drive systems)

This about takes care of as much as you can inspect without digging into the sucker.

If it passes muster this is about all you can do to tell what shape its in.

Now I will say this.
I have done the previously described protocols and drove a rig home only to have a head gasket blow a month later.

There is no way to tell absolutely what shape the thing is in.
To give an example

Bought a High mile Suburban off ebay.
The rig was in SanDiego Cal
Flew to Socal, met the seller, we look the rig over, he starts it up and its running fine.
(1995 2500 Burb 4x4)

Chating for few minutes and getting ready to hand him the check for the ballance owed.
All of a sudden the Burb starts missing, smoking like crazy (smells of diesel fuel and antifreeze) puking coolant out the overflow top hose hard as a rock.


Hmmmmm decided to blow a gasket right there. had this happend 20 minutes later I would have been out on one of SOCALS myriad freeways on my way back to Oregon.


OMG what a mess that would have been.

Cost me a flight to SanDiego then home again. Got all my Money back though for the deposit on the rig.

Not to try and scare but simply to point out that these things with a Buttload of miles can give up even though they seem fine.

Anything over 200K miles should be treated with the idea that it will need something in the way of work.

Hope this helps to scope out and purchase a used diesel.


best

MGW
 
I copied this from another post, add in any additional thoughts what to check for, and when finished we'll add it to the reference area. Keep to technical recommendations only, as we want to make it reference material.
 
Just a side note.

Ask the seller to leave the rig sit as you want to start it cold. (If you have answered an ad on the phone)

Another thing to be aware of is the sellers body language all the while you are letting the engine warm up.

If the guy is pushy, pushy, pushy about getting you to buy it right quick he may be trying to hide something long enough to get your money.

If you ask the seller to leave the engine cold for you to start and its all warmed up when you arrive there may well be something that the seller is hiding.

Like maybe he needs to use ether to start it as the glow system is dead ???

Just things to be aware of.

MGW
 
Look for signs of GM Cooling tabs in the overflow tank. It is a quick hide a leak before sale trick. I looked at one one time and you could still see powder from when the idiot just put the stuff in. Look carefully in that tank as much as you can see(which aint a whole lot). If you pull up and he uses ether to start it...get back in your car and leave.
 
One good indicator of it's use is how many miles divided by the hours. If it's around 40mph ave, it's had mostly hwy miles and not a ton of idling. Hold the trip ODO button in with everything off for 5 secs or so to read hours (in case you hadn't heard that and it's a GM newer than '95 I think).
JM2C
 
Do the following IP test. With engine warm, in park, run the engine slowly up to 2000 rpm, hold it there, and ramp it slowly down to idle. If the rpm jump on the way up, and you can't hold steady 2000, and it just drops when you try to ramp down, the IP is toast and will need to be replaced.
 
For sure for sure

The body and interior condition is everything.

An engine can be easily replaced. (Ask me how I know this)

A rusty body with an interior that looks like a pack of rodents have been living there is far to tough to bring back. (Except for a vintage camaro, vette or some other very valuable vehicle/collector)

I have found as of late that the 6.5 TD Badge on the thing is a real bargaining chip.
Lots dont even want them any more.

My DaHooooley had sat on a lot for many months and with the issues it had (small but ominous to the non 6.5 nutcase) and the folks were willing to deal readily.

One can usually tell a lot about how the P O took care of a rig by the condition of the interior and body work.

If they present you with a day planner with every oil change, fueling stop and other work noted you can be sure they were very anal about taking care of the thing.

I bought a rig once that had just that,all neatly written down with the date, time mileage, place etc.

Every repair was noted with the cost and who did the work.
Tire changes, miles per set. Times that they were rotated and on and on.

Now most folks dont do that sort of thing.

Me, Im lucky to keep oil changes on time.
Always yank the stick and check it at every fillup though.

MGW
 
Pull the codes with a paper clip on OBDI or visit an autozone on a test drive where you know there is a scanner. Buy one if you have to as the OBD II readers are cheap!

Inspect the front end for cupping on tires, slop in the steering, and blown grease seals. The 6.5 TD is in a body style known for needing upper and lower ball joints done often.

Does the cruise control work? No: may be bad switches to a bad IP.

If it is an auto trans...
Pull the dipstick look for rust on the dipstick - a sign the radiator intercooler tank is leaking with a pinhole. If so it will need a trans overhaul if left leaking long enough, can be as low as $850 in and out rebuilt 4L80E on a 4x4, and tank repaired/bypassed with external air to oil cooler. You may get away with a trans flush and cooler repair/bypass. Coolant eats the water biased friction lining glue on clutches and will rust up/lock up bearings resulting in expensive hard part damage.

Count the shifts. Gear missing?
Run it on the freeway for 10 min. Does it drop out of OD?
Could be a simple sensor or major trans issue.

In any case figure on $1500 to recondition any used vehicle you buy. A bad transmission or engine should lower the price but not necessarily a deal breaker. Just know the cost and how far you are willing to go. A daily driver vs. a farm truck for example who cares if the front end is shot on the farm.
 
One good indicator of it's use is how many miles divided by the hours. If it's around 40mph ave, it's had mostly hwy miles and not a ton of idling. Hold the trip ODO button in with everything off for 5 secs or so to read hours (in case you hadn't heard that and it's a GM newer than '95 I think).
JM2C

:mad2: The hour meter on GM clusters is not accurate. Lots of them reset to 0 with low batteries, jump starting, and cranking. This reset the hour meter bug even happens on 2008 GM diesel pickups. My 2008 had 80K and 120 hours... :eek:
 
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