I may should have kept going on them, but couple other threads I started
recently about Flushing coolant system & and about fuel, injectors, & temps I think I let get too cluttered up by trying to cover too many things, so I decided to start over with new thread.

Usually when we have coolant system trouble it getting too hot, right?

I'm still having trouble getting the coolant temp up to operating temp. on this 9U. I'm trying to get the temp up first place because it should be hotter for proper operation anyway. This thing has always run cool since I got it last year....never seen it over 140deg on gauge, usually 120-130. It runs good & strong & by rights should warm up.
Radiator is good & clean, no leaves,dirt, oil. No oil inside either.
Oil pressure runs about 60psi warm & 50-55 working.

Other immediate reason is if I can get temp. hotter, then I plan to use coolant to heat my WVO fuel setup that I think I can get to work on this thing. I need to circulate it thru coils in separate fuel tank, heat fuel filters & lines, etc.
I've checked gauge against my heat gun & it's low but within 5-10deg of anywhere I shoot that counts.

I even hung tarp over radiator & finally got temp up to about 185 on gauge as well as reading by heat gun. When the temp got up to this 180-185 the oil pressure did come on down to 40-45 psi setting hi idle....& 35-40psi while moving & working it with rad. covered & hotter. (to me this sounds like its still just not usually getting to operating temp for oil to get really hot & press to drop)
Oil press fluctuates 5-7 psi at whatever temp it currently is at between idle & hi idle, sitting or working.
At the 180deg or so, watching flow thru radiator cap as it warms up it went from "meandering" to flowing pretty good, not "rolling" flow, but flowing pretty strong. I felt the thermostats were opening OK.

Other day I pulled thermostats & cked. them. They both seemed "stuck" open about 1/16". Tested them in pan of heating up water & they were acting wrong. I then pulled apart & cleaned (they both were gummed & stuck.)
Then tested them both twice separately to make sure in pan of heating up water. They both started opening around 160 deg & were fully open at 180-185. (fully open looks to be about 3/16"-1/4"??)

Coolant system has been about 50/50 mix, but needed flushing out, but other than some usual stuck rusty scale where I can see it, the system may not be as dirty as I first thought. However, I wonder if some of the "dirty" & rusty coolant I drained out may have been some stop leak. But it didn't look like anything I'm used to seeing....like Barrs Leak. When it splashes & drys it leaves a fine, dusty yellow "pollen" looking dust.....

Finally got it all back together yesterday & worked it 2-3 hrs pretty hard. Ambient about 70deg. outside. Ran it with just straight water & drained & flushed out twice. It never got over 120deg on gauge or 130 by heat gun.
Finally hung tarp over rad to get heat up, which it finally did...180 or so.

Only other thing I did was tap into 3/8" flanged fitting on thermostat housing,that Old Magnet mentioned, looped back to 1/2" drain fitting on lower rad. drain in cast 2 1/4" rad. tube. Water can circulate before going thru thermostats & into upper rad. I wouldn't think this should let coolant change temp much.....
(This is where I planned to tap in for hot coolant supply for WVO heating. But for now it's just looped with ball valve on each end.)

Only other thing I can think of is maybe waterpump not flowing enough....but I would think I'd have overheating problems then.
When I get time next, I think I'll ck. flow into bucket thru that hose tapped into thermostat housing.

Sighhh...think I'll just run away from home....sighhhh:(

BTW, I quit running WVO in my 7.3 trucks...trying some store bought Bio though. Seem to run OK too.
I decided it's not worth chance of trouble, the hassle or worry. Seems that round here they're starting to hollar about running WVO on road.....It's a shame but they looking at it same as offroad fuel.

I,d get rid of them old thermostats & put two new ones in & see what happens.It seems it should get up to operating temp. if they were any good.Might pay to install a new temp gauge too if it,s an old gauge & not changed for years.It,s very odd for it to run cool as the thermostats control it to be right if they are working correctly.

There are some variations of how the regulators a made but they can be disassembled for cleaning.
I suspect yours are sticking in the open position when installed in the engine.
Might try a good cleaning before replacement.

Thanks OM. Pics look like what I finally found in my manual.
Yeah I pulled them again last night & they were stuck open part way again. I had them apart other day & cleaned them & tested...seemed to be working OK then.
But now....I guess they're old & tired....I know how they feel.
I'll probably just order couple more today if I get time. Got a day full of other crapp. Darn Dr.'s need to make another boat payments...so I guess I'll do my civic duty & go see 3 of 'em today:D
Checked with Cat other day & for only about $48 ea. plus frt. I can own 2 new ones:(

Curiosity will make me want to tear these old ones apart again just to see how they got the best of me though!!!

I probably shouldn't entice you with this but the large diameter flange automotive type work and will sit nicely in place on top of the retainer rings.

Got'cha Old Magnet. I'll ck it out. Thanks:D