Cooling Issue

[d9pierce]

Hi Everyone,
Recently I have had an issue with my 1995 K3500 6.5L TD on cooling issues. When I come to an idle for any amount of time my heater goes cold as if its not circulating and some times it would create engine to start to over heat, and then I would have to go releive pressure off of the system by opening up the bleeder valve and letting out steam, then it would work fine. This weekend I replaced the entire cooling system. I used a new Rad, new Heater Core, new Hoses, and Walts up grade dual t-stat and 130gpm water pump. It no longer starts to over heat however the temp coming out of the heater still goes cold after about 2 minutes?

Any suggestions to why this would happen. I also heated truck upto op temp, blead off until came out full stream from bleeder, and topped off after cooling it down. Its like there is a big air bubble in this system or something but I dont know?

Any advice would be just wonderful? Makes no sense to me!

Dave Pierce

[trukdoc]

...you won't like it...it's called a blown headgasket...or maybe a cracked head...compression is leaking into cooling system forceing out coolant...

[d9pierce]

Thanks,
That is pretty much what I figured. I guess its time to go ahead with a new long block!

[Husker 6.5]

Odds are on at least one crack between the intake and exhaust valve seats in one, if not both, head(s). The symptoms you describe show a pretty massive internal coolant/compression leak, my '94 did the same thing, I had three cracks on the passenger head (2,6,8) and two in the driver's (3,5). Once you over heat, the effects domino and the other head will usually sustain damage too. Pull both heads, even if you find cracked seats/blown gasket on the first one you pull, pull both and check the head and gasket. Better safe than sorry for taking a short cut and have to do it all over again. The cracks between the valve seats can be hard to see, use a 10x magnifying lens or some Prussian Blue to spot the cracks. Often with the head cold the cracks are only .001-.002" inch wide and are hard to see, when the temp rises the cracks open up and coolant is dumped into the combustion chamber on the down stroke and combustion pressure forces gasses into the cooling system near TDC.

[d9pierce]

Thanks everyone and definately dont want to take any short cuts. Thsi engine is cursed so I am just going with a new conversion long block and use my bolt ons that are in good shpe and change out the rest. I just cant have a truck that everytime I turn the key on I have to ask myself is this the day! So with that I have a seven week job in South Dakota I am starting tomorrow and am going to drive it like it is and then change it all out after that is over and before starting the next one. I like the truck but after all of this and a new engine, it better not give me a hit of problems or I will have to go back to gas! I have never had so many issues with an engine in 35 years of driving!

[Husker 6.5]

I hope the motor lasts that long.

[d9pierce]

me too, lets pray now, LOL!

[grancito]

Someone a month or so ago had success with coolant additive to seal the cracks, try a search on this site.