Is head gasket kaput? (long)

[DaveKay]

Searched and found a handful of posts regarding head gasket issues but did not find definitive answers that I need. So--- I'm asking for a bit of advice and perhaps direction regarding potential head gasket problem diagnoses for 1986 Chevy 6.2 J motor, displaying odd cooling system issues.

This is an original, complete, un-hacked, M1008 1-ton pickup, CUCV surplus vehicle w/approx 90K miles of which I've put 10K and have made a few maintenance-type repairs. Otherwise, the vehicle is bone-stock everything. Truck is daily driver.

FWIW: Am relatively new to diesel engine repair but have fair amount of gasser experience and am not fearful of tackling R&R projects, even when the going gets tough.

Issue one: flushed & filled cooling sys in March this year ('13) and kept watch of coolant level at overflow tank. Added half gallon here and there for a few weeks when I felt satisfied that system was maintaining coolant level full when hot.

Two weeks ago while stuck in traffic at a crawl, engine idled somewhat higher than normal and a bit rough. Heard thermo-fan loud humming. My cheesy temp gauge went to over 190, (never read over 150 prior to this date) and something told me engine was hotter than norm so pulled off freeway to check. As I always carry a couple gallons of water I was amazed when radiator took a gallon and a half. Engine temp gauge went down and I proceeded home to add more green stuff with vows to keep better watch on coolant level.

Issue 2. Coolant levels steady for two weeks but small EXTERNAL leak observed at water pump flange/timing cover joint, and after shutdown UPPER radiator hose leaked a good amount of coolant from the radiator nipple, running down the drivers side radiator tank. Upper radiator hose was VERY firm to the squeeze test and once cap pressure was released it went back to normal, semi-flex-able. Looks like there's lots of pressure in cooling system.

Issue 3: Diagnosis--- gave thought to taking truck to pro-mechanic for complete engine diagnostic, including fuel sys, but have yet to find a recommended shop. Meanwhile, what would non-pro types, like myself, do to test and make educated determination whether head gasket or other issues are involved, with non-pro facilities and expensive tools?

BTW: Have ALL three DieselPage books on 6.2/6.5 but STILL--- cannot get my basic questions answered there--- that being; what is this weird cooling sys behaviour and before I tear into engine--- am I head gasket headache bound?

Please feel free to shoot me full of holes and Kind regards!

[joeq]

If it were mine, I'ld do a pressure test of the coolant system 1st. I've had my share of blown head gaskets,(maybe 5 on my 6.2, both sides), and every time the coolant leaked into the cylinder.(Liquid lock). One time, I even drove the truck home from work when it happened. Just removed the glow plug from that cylinder to relieve the pressure. (Talk about a noisy ride).

[sctrailrider]

One way to see is to remove the belt that turns the water pump, then remove the thermostat and start the motor and look for bubbles coming up the water neck, the bubbles can be seen coming from the side that is blown inside the water neck..

And when cold does the top hose get hard soon after you start the motor???

Have you cleaned the fins on the rad stack yet, might be full of bugs & dirt.

Make sure you only use AC Delco stats in these motors, the aftermarket stuff doesn't work very good..

[Robyn]

A bad head gasket will normally present with coolant being blown out the overflow.

This will happen right away when the engine is running, and is not an on again off again thing.

If you were able to run for several days without an issue, I really think that the leaks you spoke of may be the issue and not a head gasket.

When these engines lose a gasket they will really blow the coolant out, and quick too.

Fix the leaks and then see how it does.

Normally the top hose can get fairly firm, as the system has a 15 psi cap, and can normally run with good pressure.

An extremely hard hose with coolant blowing out, even cold is a sure indicator of a bad gasket or a crack??????? somewhere


Missy

[neo]

unfortunately, I have fought this fight multiple times, more than i should admit. If the head gasket is truly bad, you will hear a difference in the tone of the engine, for certain. You can do the trick as suggested above with the belts and t-stat, that is a good one. Also, do a compression test. The compression test is how I ahve found mine (after suspecting somehting due to the noise.) The noise I am speaking of is a knocking that is like a bad injector. Each time I have had an issue, there was enough coolant leaking into the combustion chamber to cool the charge so that is would not completely combust. THe knock coupled with coolant overflow and finalized with the compression test has always found mine.

[DaveKay]

Thanks to all, your comments are much appreciated.

Addressing these points:

1. cooling sys pressure test hopefully Sat or Sun--- replace radiator cap w/new 15lbs unit. Also possible compression testing if proper rig is acquired.

2. Will try the cold start/running upper hose feel test Sat/Sun. Will observe overflow tank for air bubbles.

3. OK, remove water pump belt & t-stat, looking into water neck assuming top hose removed I guess. Won't I have a bunch of air coming into cooling system bubbling up at this point? Clarification here.

4. That the typical blown HG will blow coolant out the overflow, in my strange case, coolant is being blown/pushed not out of overflow but at the upperhose radiator tank nipple. This does not leak normally and the accompaning VERY firm upper hose makes me wonder why high pressure is not opening cap to release to overflow, then where else can coolnat go but out that upper-hose nipple?

5. Am very reluctant to drive truck right now for fear of making heads/block/gasket sealing surface/problems worse than they may already be.

[DaveKay]

Results

1. bought cheapo Harbor Freight cooling sys pressure test kit--- PLUS--- rented HD cooling sys test kit from O'Reilly's.

Rental kit pumped up to 15psi and revealed TWO leaks; one at the t-stat flange/gasket and other at my UPPER Radiator hose -which had been blowing out coolant when hot! DUH?

Fixed both and later test held 15psi for a few minutes then slowly bled off to 11, then 9psi within approx 30 minutes. Right now it's nearly an hour later and still holding 9psi. Sound like a HG problem to you guys?:o

Harbor Freight kit was somewhat useful but it would not hold pressure very long, prolly the pump itself leaks air, as expected, cheap junk. But it does have a bunch of different adapters that may be useful for things other than radiator pressure tests.

NOTE; when cooling system pressurized to 15psi UPPER RADIATOR HOSE is very, very hard, almost extremely, like it's abnormal--- guess it is not. As we learn about the different ways of our respective vehicles we hopefully pass them along that they may help others.

Seems my HG scare was unfounded. Will now drive truck for couple of days and be vigilant. Daytime temps will be hitting 110-plus by weeks end. We'll see how it goes.

Thanks again to all!;)

[joeq]

110*!!! Where do you live, Arabia? Temps like that, i guess you "do" need to keep up on your cooling system. Good luck with it.

[DaveKay]

110*!!! Where do you live, Arabia? Temps like that, i guess you "do" need to keep up on your cooling system. Good luck with it.


HA~!! My home is the High Desert of SoCal, 3200 ft altitude... heard of the Mojave Desert? So 110F is typical Summer fare but those spells don't last long, typically a few days. Mostly in the mid to high 90's w/heatwave-like conditions to 110 and above. Heck, Death Valley, about 90 miles NE of us, gets 125 and up!

Also pleased to report that truck passed a long, 25 mile, slow offroad trail this afternoon with flying colors, no heat related problems or strange cooling sys gremlins. And the mythical 'bubbles' in the overflow tank supposedly indicating HG probs--- are not there.:)

Regards

[sctrailrider]

It's amazing how just a few small leaks can make it seem worse than it really is ....... glad it up & going......

[joeq]

I "do" like a happy ending. (with easy fixes). Good job.