Hello and adventures in cooling a 6.9

[nic55kel]

Bought this very nice 1986 F-250, C6, GV, 6.9 from a younger guy who had it as a project but had to give up as needed $.
Running very hot when I acquired it. Radiator was all scaled up and plugged. He never really figured this out I guess, anyway put in aluminum rad and truck ran sweet.
No observable blow by, starts real easy anywhere from cold to super hot. Return lines all replaced, 7.3 glow plug system, new batteries, good tires, brakes just done.
PO told me he had just replaced the thermostat, have read all horror stories about non OE thermostats and had it on list to get to.
Anyway have put a few hundred miles on it and all good until yesterday driving along and the temp gage pegs. Luckily I notice it just before it boils over. Pull over and the coolant starts to back up into the overflow and fills and leaks out just a little coolant. Cools down and sucks it all back into the engine. I figure that is just about as close to cooking it as I would ever want to get.
The fact that it pushed the coolant out the bottom told me the thermostat had failed closed. Tow it home and pull the thermostat - it had mechanically separated and I guess the pump pressure held it in the closed position.
Well will be getting ford stat for sure now.

Just want to thank all the great contributors to this site, it is a goldmine of information and although the 6.9 lacks power I must admit I am really starting to love its sound and simplicity and hopefully soon its reliability.

 

[icanfixall]

Welcome to the forum. That note about the po changing the thermostat and you buying the rig. then you heat up the engine. Then towing it home safely and removing the thermostat. Well the pics tell me thats the wrong thermostat for sure. your posting is not too clear but I feel if you replace the thermostat with a 192 degree factory correct one it will be fine based on what I think you posted here. The factory part number is listed in the parts bin forum but here it is off the box. RT-1049 E5TZ-8575 C... The 8575 is the Ford part number for all thermostats they make.. The E5TZ is the model and year engine this stat fits. Don't have any idea what the RT-1049 means. These numbers are found on the end of the motorcraft box.

 

[nic55kel]

Thanks Icanfixall for the encouragement.

My problem with the aftermarket thermostat is that it is too long. When it fully opens it hits a high spot in the block which flexes the metal which then quickly fatigues and breaks and then the sleeve of the thermostat is held closed by the pump flow/pressure.

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It also seems that I am missing my cold advance, fast idle switch. Did any of these engines come without one? It seems and odd thing for someone to remove??

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Anyway put in the correct stat and the truck runs really well. It appears no damage done - yeah!

Put some mechanical gages in that I had laying around. Engine runs at a pretty steady 190 and 40 psi at cruise - 65mph.

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[Can30Diesel]

Welcome to the forum! I have been happy overall with my 6.9. My thermostat failed on me while I was pulling a trailer, it was all kinds of fun.

The 6.9 though not so powerful is a workhorse of a motor. If one adds a turbo then the motor wakes up a little, thats in my plans for this truck one day.

 

[riotwarrior]

Welcome to OB, glad you picked up on the info here, and ya stock FORD or IHI thermostats only!

Glad you managed to get it running well. Now find a turbo and enjoy it.

Take a look around and read through FAQ's and Tech section, also have a gander at the hall of shame...so you don't spend money foolishly on bad vendors.

Nice to see another Canadian here too, great stuff. I'm impressed with how many Canadian members we actually have here.

Again, Welcome to OB

Al

 

[icanfixall]

Thats a great pic of the correct stat compared to the wrong one. also that hole in the underside of the thermostat cavity is the bypass. When the stat is cloed coolant flows thru that back to the water pump. When the stat is open it grows down to plug that holes fairly well stopping much of the flow bypassing the top of the radiater.

 

[dgr]

Holy cow! 13% LMNOP tax.

You should ask the prior owner what kind of coolant that is if you don't know.

 

[tbirdfiend281]

welcome, looks like could be some extended life coolant of some kind. I know international is pushing the red stuff. Turbo's are almost a must buy, and they are usually under a grand to, so cheap for a turbo setup.

 

[nic55kel]

Thanks for all the replies.

The coolant is from NAPA, old school glycol, low silicate for HD diesel and precharged with SCA. Pink maybe a Canadian thing.

I guess living in BC that a turbo would be almost essential.
Flatlander here have to take a trip to see a hill.
It gets up to highway speed pretty fast but there is not much extra and passing can be exciting.

It seems that when I moved my fuel filter to change the thermostat I must have disturbed my return line and cap on injector #1.
It now leaks a tiny bit and I have the sputter and die on starting then a long crank before it will run.
PO tells me they were done recently. Anyone have any luck just doing one or should I just plan on doing them all.

I also always have a bit of black smoke when cruising, nothing really bad but very visible - is this normal for IDI? truck starts and runs nicely and gets decent mpg so no other indicators of worn out IP that I am noticing.

 

[Knuckledragger]

Black smoke may be one of several things, including weeping injectors or an adjusted IP fuel screw. Almost certainly a fuel issue, anyway.

Return line, O-ring and caps cost $25 to replace, an easy afternoon project. PO may be telling you what he wants you to hear, and "recent" is a relative term.

 

[tbirdfiend281]

ya, return lines and o rings are quite gravy, I got mine knocked out in about an hour, and that's with a turbo mounted.

 

[Full Monte]

Remember...you have to burp a big air bubble out of the top of the head in order to get it to cool correctly. Towcat says you can fill the radiator with the nose up high, like on a hill.

 

[tbirdfiend281]

So you guys are saying that driving an IDI or even idling an IDI at operating temp, will not bleed air from the cooling system?

 

[icanfixall]

Yes it will but the easiest way to bleed the trapped air is lift the front of the truck. The thermostat housing has a BB in it thats there for bleeding trapped air but sometimes its stuck. Grab the top hose and squeeze it a few times listening for the clicking noise of the BB opening and closeing./ If you hear that you wont have air in the system. Watch the coolant overflow tank and keep it full.As the engine runs it heats up and cools down sucking coolant back from the tank. Once that stops you r free of air.

 

[nic55kel]

My truck does not have the cold idle/advance switch. So when I refill I pull the plug where the switch would be and when the coolant reaches that level I know that the block/heads are close to completely full. I also made sure that the air bleed ball bearing was free in the thermostat housing so my coolant level did not noticeably change after I started it up.
I got lucky on the return line it was just a loose clamp on the hose from the filter to #1 injector return. The return hoses are not at all brittle and I can rotate the caps a little on the injectors without it leaking so I think the o-rings were all changed just like the PO told me.
I am thinking that I will install a manual cold start advance/fast idle switch, the truck starts easily but it helps if I gently touch the throttle pedal.
I have bought a fox-valley luminosity timing adapter and hope to check the timing this week.
I intend to mark the balancer at 5 ATDC and see how close I am to that.

I have now put about 1000miles on the truck, have changed the trans fluid and screen and it is definitely growing on me.
It does not have a lot of power (I usually drive an 04 E450 with 6.0) but plenty for an old timer like myself.
What I find funny is that the engine gets quieter as it works harder. It has the loudest rattle at the lightest throttle.
It is nice to go up a rise in OD and have the engine quieten right down.

The amount of information on this site is amazing and thanks to all for providing it.