99 stroker intermittent overflow in radiator reservoir, hot cold heat

[jas_stang]

just bought a 99 f250 xlt crewcab with the 7.3 automatic with 252000 miles on it, person i bought it from said his mechanic thinks it has a cracked head. he put 12,800 in repairs in the last two years- new tranny, transfer case, hubs, spindles, water pump, alternator, heads, hoses and tons of other stuff the dealer did. the truck is in great condition, just needs cleaned up. here are the symptoms; when i test drove it, i rode it hard and fast trying everything out making sure 4x4 worked and all that for about 15 minutes, when pulled into the lot the reservoir for the coolant had fluid spewing out from the cap. after buying the truck ( $4700) i drove it 100 miles home and it never leaked a drop, and now i haven't been able to get it to do it again. the heater will blow cold even when the engine temp gauge is in the middle of norm and then it will blow hot for a couple of minutes and go cold, then hot, then cold. i checked the upper rad hose today with engine running and warm, heater blowing cold, upper hose and heater hoses were cold, pinched off hose for a few seconds and i could feel pressure surging when released. chekced the fan clutch with engine warm and doesn't have much resistance to spin by hand, so I'm going to change that, had reservoir cap pressure tested 3 times, 1 time it dropped to 14 psi, the other two it relieved at 16 and maintained, so i put a new cap on it and drove it hard again, it didn't leak, but i still had the heater blow hot, then cold. any ideas on what to check or look for, anyone know of a good test kit to check for combustible gases in the coolant. thanks in advanced for the help, i hope i got a good deal.
jas

[jas_stang]

any ideas? i checked the coolant level yesterday after letting it sit for several hours and the level was down to about 2" from the bottom with engine cold. added just over a gallon and got the level in between cold min and max, started the truck and let it run 10 minutes and it started spewing coolant out of the reservoir again through the new cap, the engine temp was normal, heater was blowing cold air, upper radiator hose was cold and i could pinch it and couldn't feel a lot of flow. the waterpump looks brand new and i saw a small leak around the t-stat housing, so i will pull the tsat and install new. i have never owned a diesel before and would appreciate any ideas. thanks in advanced

[jas_stang]

what is the best way to test for these, how about the napa block checker kit for $50, anyone used it? it doesn't smoke, no water in oil, no oil in coolant, just overflows the reservoir and heater blows hot then cold repeatedly. anyone?

[jas_stang]

has anyone pulled the heads on their 7.3 stroker. i have never worked on a diesel before and was looking for some things to look for. I will probably start tearing down to pull motor and heads in the next month or so, any tips or tricks would be appreciated. thnaks in advance

[jas_stang]

did combustion gas leak test, found drivers side the culprit. tore down and removed head, found blown head gasket tracing to water jacket. checked the head and it has .004 warpage in the center, anyone know the tolerance specs for head warpage on this, the bolts were very uneven on torque, anywhere from 110 to 80 ft/lbs. 252000 miles and cylinders are barely broke in, no dusting and minimal wear to cylinders.

[jsmall]

On the subject of intermittant heat, my old toyota will blow cold of the coolant gets low. I had a crack in the reservoir, and over time the level in the radiator drops as it pushes coolant into the reservoir when the engine is hot then has no fliud to bring back in when engine cools (since it all ran out the crack). Filling the radiator always brought the heat back. The temp gage never read hot as the coolant wasn't that low.

[MNWoodcutter]

I have a 2002 poerstroke. The radiator reservoir overflows sometimes. The heat goes in and out. I replaced the thermostat and was then told to replace the upper housing to the thermostat. It does not overflow as often but still does and the heat goes in and out even though temperature of the coolant stays where it should. When I stop at a light for to long the truck will start to cool itself and the temp guage drops. Upon acceleration it heats back up and the heat starts to work again.

[MNWoodcutter]

I am also changing the head gasket. The gas test revealed I have a bad one. There is only 62000 miles on the truck. This is not a common problem with the 7.3 but can and does happen is what I am finding out.

[SCUFFY828]

with that many miles on that truck ,you better look at the injector cups ,will give same reading and symptoms as head gasket will with your tester,my opinion i would think more about a injetor cup than a headgasket, not that it couldnt be a headgasket ,but would not want to put it back together and still have a problem

[jas_stang]

i've had the truck back together now for 5 weeks, put over 700 miles on it, it runs great, no problems. the head gasket was definitely blown, for that many miles it is in great condition, i am impressed with the motor, the only problem i am having is with cold starts, glow plug relay checks out, glow plugs and harness good, it has been around 5-35 deg F here lately, i think i need to try and find thinner oil, running 15-40now, if plugged in it usually starts on try 2. if not plugged in it will take several tries and when it does start the idle surges from 500-800 and the truck rocks, then it will smooth out after 15-30 seconds. it is a great running truck.