1994 4.0l OHV overheating

[RonD]

So I bought another 1994 4.0l with blown head gaskets, both sides, cylinders #2 and #4, glove test

Sent the heads out to machine shop, and much to my surprise neither was cracked
valves checked OK so they surfaced them.

Flushed the block out, had water pump off
Flushed heater core, good flow

Reinstalled the heads and all went well, just normal BS, lol

Put in new water pump and thermostat

Pull radiator and flushed it, and did flip test no blocked tubes, looks fairly new

All back together, filled with water, heater hose off to let air out

Started it up, no white smoke
no water leaks

...........but after only a minute or two temp gauge started to go up, but heater was still blowing cooler air.
Warmed up to below 1/2 like normal, heater got warm, and you could see the temp gauge drop when thermostat started to open, and upper hose started to get warm

Then it starts to go over 1/2 on temp gauge and starts to over heat, if you drive it hard it will overheat

So...............I am puzzled

I pulled back the shroud and felt radiator, nice even heat and cooler at the bottom
so new water pump seems to be working, and thermostat

If I let it get hot enough I can shut it off and I can hear bubbling in passenger side head, drivers side is quiet
The heads were not flushed, yes I should have done that, lol

Any ideas on what I am overlooking or if I can clear any blockages without head removal
I may pull thermostat and see if I can snake a smaller hose up into the passenger side head and shoot water in, that should be reverse flow

 

[RonD]

Re-did Glove test just to be sure, and all is well no cylinder leaks

 

[alwaysFlOoReD]

Wouldn't the machine shop dip the heads before starting work on them?
Otherwise, sorry, no ideas.

 

[RonD]

Didn't look like they did, head was cleaned a bit but not with chemicals, maybe a pressure wash.

If all else fails I may pop the front core(freeze) plug on the passenger side head, I forgot they were there, just a few bolts to pull alternator and bracket off.

Its a puzzler

 

[Uncle Gump]

I had a water pump impeller on a reman pump that would spin on the shaft... the warmer the engine got... the more it would spin. Took awhile to figure that one out.

 

[19Walt93]

If it has a fan clutch it may not be engaging.

 

[RonD]

Fan clutch tested OK, but I swapped around the two fan clutches(from my working 4.0l), no change in either, so both work as designed

Yes, "new" just means never tested now a days, lol, so I may swap in the old pump, but circulation "seems fine"
When thermostat opens, the upper hose heats up pretty fast and then the lower starts to heat up with in a few seconds so flow "seems OK"

 

[RonD]

I "think" I got the passenger side head passages cleared

I connected garden hose to intake heater hose, which, in essence, back flushes the heads if thermostat is closed
Had lower radiator hose off, and heater core plugged
Used full home hose water pressure, maybe 18-20psi
Then refilled with water, ran engine until thermostat opened then let it cool down.

Repeated this 3 times and seems to have helped

Going to run coolant now and see what happens

 

[G8orFord]

OT: 18-20 psi? I know I'm probably an exception, but I've got 80+ psi at my house. I had to install a regulator to keep from patching pipes all of the time. I left the outside faucets unregulated. That's nice to have when you need it.

 

[Snoranger]

I've got well water for my irrigation system and 1 hose. My cycling switch low and high limits are set to 60 and 80 psi. There's not really a noticeable difference from the pressure on the other hose that's on city water.

 

[G8orFord]

HUH?

 

[RonD]

The reverse flush worked, no more over heating, drained the system again, lower rad hose, didn't see any major grit or grime so not sure what was in there , but its somewhere else now and not causing an issue