I have a 1983 olds with a 5.7 diesel thats running warm but hasn't boiled over. I've checked the following rad cap off didnt bubble or foam, oil level or antifreeze level didn't change. heres what i noticed the engine fan stays the same all the time even when its running warm i was told it has a thermostat on it and should speed up when the car get warm. Another thing i noticed is one of the coolant hoses that runs to the heater core is hot only half way so i bypassed that still the samething. I would appreciate any info as i am need to these cars. The car was running at 250 F when i parked it

Could be head gasket. Mine got to 260 f when the gasket blew. The coolant didn't blow out either. One of the head bolts head had snapped off was the easy way for me to tell it was the head gasket. Also it was the updated head bolts too and it was the one under the valve cover. You could start of with changing thermostats and making sure your radiator is clean.

I figured it would be a head gasket but on a cool day it runs about 190 f. If it was a head gasket wouldn't it run hot all the time. Radiator is good thinkin it might be the thermal clutch on the fan because when its hot the fan don't go any faster than when u first start it.

One of the head bolts head had snapped off was the easy way for me to tell it was the head gasket. Also it was the updated head bolts too and it was the one under the valve cover.Been awhile since it happened, but I saved the bolt as a souvenir.

I figured it would be a head gasket but on a cool day it runs about 190 f. If it was a head gasket wouldn't it run hot all the time. Radiator is good thinkin it might be the thermal clutch on the fan because when its hot the fan don't go any faster than when u first start it.
Sounds like a cooling problem and probably not head gasket. Could be fan clutch since its supposed to kick in when the engine temp gets high.

Another thing... because I wanted to keep my motor cool, I put on a constant engaged fan clutch and a 160 f thermostat. A warning about the constant fan clutch is it will make noise all the time cause it is engaged all the time.

One way to check if it is a head gasket is to pull the fan (water pump) belts off, drain the radiator down below the level of the stat, pull the stat housing and stat out of there and start the engine and look for bubbles. This will also tell you which side has the blown gasket. I wouldn't run it too long like that though.

If your fan clutch failed off, the engine should cool down if you start running down the road. If it only begins to overheat at idle, this is a good place to start.

In regards to a cooler thermostat, one thing many people neglect to mention when recommending this is that you will get accelerated cylinder wall wear if it runs too cool all the time. These engines were designed with a 195 deg thermostat. I would recommend installing a Motorcraft (only -- no knock offs, the aftermarket ones have a seal built into the rim of the stat and they tell you to toss the one on the housing) thermostat for a mid-80's 6.9L IDI International Engine (can't take credit for that idea -- DieselOlds came up with that). This stat is a 192 degree model and it will flow more coolant. Running an engine too cold all the time is a slow death that will catch up to you years later during a rebuild.

With all that being said, one of the first indicators of combustion gasses in the coolant in this engine is losing your heater performance. I believe you mentioned that at one point. The heater core is the highest point in the system so the gasses will head there first.

Almost forgot, if it tends to overheat under a load or at higher RPM and none of the above apply it *could* be the impeller on the water pump is slipping on the shaft. Personally I've only seen this on a few specific models over the years, not on this application yet. Maybe you're the first one! Let us know what you find.

on a cool day i can drive it around all day and it gets up to 190 to 200f. I noticed the hose going from the water pump to the heater core even when i bypassed it to where the return line from the heater core goes on the engine is cold only about 4 inches is hot by the water pump. On a warm day when its gets warm the fan seems like it dont kick in.

I don't know how this car was maintained, but you could have 2 or 3 problems. One being an ineffective radiator, a failed or failing fan clutch and a stuck closed heater shut off valve. I have a Cadillac and the climate control system closes the valve at the passenger side intake manifold to the heater core whenever the system decides to recirculate the interior air (max a/c). If this valve is still there, you can either test its operation or bypass it altogether.

Another possibility is still the failed head gasket, if the heater core is filled with combustion gas, no coolant will flow through it.

problem solved it was a fan clutch runs about 180f now so sweet deal. I'm thinkin got vacuum problem as well i got no cruise and was told the pop button for the trunk is run from that and it dont work. I was also thinkin that why i got no coolant flowing through my heater core because the vacuums not openening the valve to let it circulate. Any thoughts would be greatly appreciated. Trying to get this baby runnin good so i can drive it to work.

I just got an '83 engine out of a DeVille for a rebuild in the garage and frankly was shocked at the crud I found in the water jackets of the block and head. Found ports clogged shut, the water valve on the back of the manifold to the heater core was flat out plugged solid. When I got the engine home I drained the coolant, some fell on the floor. It was super dark green. After it dried it turned bright orange. I'm wondering if someone dumped "head gasket in bottle" in there. Of all crazy things, no head gasket failure, it had an intake gasket fail, someone assumed it was a head and dumped in mechanic in a bottle LOL.

I had a B*%&H of a time getting that valve out of the manifold using a 1 1/2' long wrench, and my engine was on an engine stand in my garage. One of the studs holding the thermostat broke even after working it with PB blaster.

If someone did that to your engine, GOOD LUCK. That stuff is MISERY in a bottle. I sincerely hope that didn't happen here. You might consider spending a good day flushing the whole thing nice and thorough. On the final fill go with 50/50 green coolant and distilled water. Stay away from Dex-cool, it's hell on gaskets, even the ones it was made for. Also the all makes all models stuff is what's known as HOAT coolant, it's Dex-cool with some additives. Green stuff FTW. Change it every 2 years.

With that being said, that valve gets vacuum when the system goes to max a/c. If it doesn't have vacuum and there's no flow, its either plugged shut or stuck closed.

I also found a 180 deg thermostat in this engine. Again, that's not a solution to anything. Those thermostats are all the same diameter for output. That's why I recommended the Motorcraft stat for the 6.9L, it flows more. Putting in a cooler thermostat for an overheating problem reminds me of the people who would jump in my car when it's hot and mash the temp button from 72 to 60. Like the car's gonna cool off faster?

The engine currently in my car is in pretty decent shape and the cooling system was maintained. I flushed it and put in the 6.9L thermostat (192 deg), and noted that my outlet temp dropped from 205 to a steady 195 on a hot engine, in 95 degree weather here in FL with the A/C running.