Been a while since I've been on! Mainly because of work and also because I haven't had many issues. Till now. Bought a new truck a while back, 1971 SC/SB with a e99 7.3. Runs great. Recently I noticed it would push a little coolant out of the stand pipe and would hold pressure for days. Started by replacing the Tstat, cap, and coolant. Water pump looks newer. Problem remains. As it gets warmer, it starts to push all kinds of coolant out of the cap, still holds pressure.

No mixing of fluids as far as I can tell, so I am kind of doubting a blown head gasket. (as well as because the engine is 100% stock). Ive done some reading and many suggested cracked injector cups as causing similar problems as far as holding pressure and puking. Any ideas?

 

Also, heater core is bypassed so I know it isn't an air pocket there. I also know NAPA sells a kit that you use to test for combustion gasses in the cooling system, so i will give that a shot. Any way to test for injector cups being cracked?

 

Get one of the chemical block tester kits to test for combustion gasses in the cooling system. That sucks...71 CC SB PSD swap...pics or your a liar lol



That sounds way cool!!!!!!

 

Im out of town for work/school right now but ill be back tomorrow and take some good pics. Just finished relocating the gas tank and a ton of interior work, as well as traction bars. And as always, now that my bank account is empty, this pops up Thats why big blue sits in my driveway waiting for me to find the will to touch it...was one headache to the next.

 

Out of the frying pan and into the fire.

 

So if there's no combustion gasses found, it would rule out both head gaskets and injector cups right? And they could both be suspect if it there are gasses right?

 

^^ I've been hearing that for months and still haven't gotten pics... Haha.

I think the best way to rule out injectors cups is throwing a set of stage 1's in there, just for fun . I'll come help you if you give me a few weeks notice.

 

Just texted you a few rick, cant post em from my phone though. And if your buying, we'll do them! Any idea about that combustion gas test? Just trying to figure out what to look for if it has combustion gasses in it. At that point it could be either cups or head gaskets right?

 

That rules out head gasket but not injector cups.

Injector cups can push fuel into the cooling system. One way to check is to pull all the injectors and pressurize the cooling system. Any cracks in the injectors will start seeping coolant out.

That fool PowerstokeHelp or whatever on YouTube actually has a pretty good video showing how to test and replace injector cups.

EDIT:
Here ya go:

 

Thanks for the video and info. That dude.... even a blind man will hit the target once and a while lol. So how would cracked injector cups over pressureize the cooling system?

 

The fuel system is pressurized to about ~65psi while your cooling system is only rated till 16psi. That's the pressure to when your cap will blow.

The difference in pressure will push fuel into the cooling system.

 

Right, i understand that. But that wouldnt make it dump coolant (easily a few cups in a minute) when at operating temp and given any throttle ...thats what is throwing me off. Ill definitely give it a look but this one is throwing me for a loop. Ill test and post tomorrow.

 

But the engine is not over heating? What temp does it run at?

sorry I fell asleep last night.

what kind of radiator/surge tank does it use?
You can not completely fill the OE radiator on a 71. Have to run the level at about 1-2" from the neck down.
I'm wondering if its just a mismatch in parts and not an engine part failure.

 

Not sure on exact temperature. But it doesnt go over on normal (sensor is wired to stock gauge). And will sit just under normal. It uses the PSD radiator but with no overflow tank, instead the guy used what looks to be the stock stand pipe. I fill it to about 2 inches below the cap like you would, and once it starts pushing coopant out itll push out enough to empty the stand pipe and then some.

It hasnt had this problem in the previous months, it came on pretty quick.

 

Is the cap on that stand pipe rated to the same pressure as the cap that comes on the surge tank of a PSD? id look into putting the actual surge tank back on like the engine came with... give that a shot ive never paid attention to how much the coolant expands in the surge tank, when i swapped coolant i just put it to full burped it and filled it back up never really looked at again except to make sure it was still on cold full when i check the oil every so often.