88 5.7L Heat help?!?

[Travis_Culler]

So I traded a 4.0 Ranger with 260k mi & a blown head gasket for an 88 2500 long bed w/ the 5.7 Tbi and 136k miles (Score ) but there's 2 things I was warned about when getting this truck. Theres oil leaking from one of the valve covers (no biggie) and a mysterious leak causing it to drip down the back side of the starter. I am concerned about the oil leak, but the other issue is a real mystery to me.

Previous Owner says this truck lost heat in the cab. So he replaced the thermostat, the water pump, and then removed the heater core and flushed it to make sure it wasnt clogged. The heat still doesnt work. I noticed in the overflow reservoir theres a lot of debris and almost a thicker consistency looking substance in the coolant. The temp guage shows that the thermostat is opening up just shy of 210 degrees, Theres no overheating whatsoever. Is there a common issue with these trucks that I overlooking here? Or just anything im overlooking in general?

Im no mechanic so any advice I can get with this issue, Id really appreciate it. I dont like the debris thats floating around in the overflow and plan on flushing the coolant system and refilling with fresh clean coolant.

Thanks in advance

 

[JOHNGAAA1]

Coolant leaking above the starter is a notorious sign of a blown intake gasket. The sludge in the bottle is probably some sort of stop leak, instead of fixing the real problem. Use the replacement FELPRO gasket only.

 

[GoToGuy]

You could do pressure check of the cooling system, less invasive, to determine the leak location on rear engine area.
You said leak at engine rear. But what fluid is it? Saying leak is like hearing hoofbeats, is it zebras or draft horses ? Crude in the coolant overflow, get it out , determine what it is, part of diagnosis of repair plan.
Then with this info determine your repair plan .
That's what I would do.
One more, how did you get 210° on thermostat, shouldn't it have a 195° thermostat installed, I'm not sure.
Good luck!

 

[GrimsterGMC]

I just suffered the no heat problem too and it's still winter down here so very uncomfortable when driving with no windscreen demister. The problem is simply the heat blend door actuator, luckily it's easily accessible by taking the centre vent panel out of the dash to get at it and replace.