OK need some opinions on increased temps in my 2005 Excursion.

Several months ago I had some limited " bulletproofing" done on my 6.0.
This involved EGR delete, new oil cooler, rodding out the radiator, new thermostat, and sequential tightening of the head bolts. I am also running a coolant filter.
Prior to this I was seeing high deltas on my gauges.
After the fix, everything has been super. Temps for ECT and EOT usually running in the 190s occasionally going to low 200s and deltas typically 5 or less.
Recently have been seeing higher temps and higher deltas with coolant temp running as high as 235-240 briefly. This happens in stop and go driving and while at idle. Once I get going down the road this cools back in the 200-210 range.
No codes showing on my tuner.
Went to see my mechanic who hooked to computer, also no codes. Coolant fan rpms are normal. He said the plastic fins on the water pump will sometimes come loose and not adequately circulate the coolant and this will be the next thing to check when I can leave the truck with him.

Any other thoughts on possible causes for this ?

Thanks in advance for any help

 

You retightened the TTY bolts?

 

X2. Subscribed. Interested in this one.

 

X3........

 

Ok, yeah, so the head bolt thing ...

I know this will be controversial.
The guy who did/does my work is a diesel mechanic at the local Ford place who does other stuff on the side.
His take is that the bolts fatigue and that by tightening them, letting them sit and then revisiting them at several intervals they are less prone to stretching out and allowing blown head gaskets. He recommends ( unless you have a 600hp monster) just doing this and only doing head studs if you have a failure and are having to redo head gaskets.
I am probably not explaining that well, but he claims to have done this on a couple hundred 6.0s with "no problems"

 

Perhaps I should not have mentioned the bolt tightening

Anybody have thoughts on causes for the temp issue ?

 

Never heard of that. Be nice if he could get on here and explain. I had to laugh with the first sentence though. "Ok, yeah, so the head bolt thing ..."

 

Any puking? Fan coming on? Change thermostat. See if that helps.

 

The concept behind tty bolts, is they stretch... thats what the y part is about. the y part there is no torque values.
Tighting beyond the y parts just adds to the streching of the bolt.
Trucks with the 03 style pumps were the ones eith knowen impeller issues.
Check for cold spots in the radiator core and a build up of dirt between the rad, cac and condensors.

 

Just had a new thermostat.

Fan is turning.

 

Matt, its pretty clear to me to me that your fan clutch isn't working as designed. Do this. Crank it at home and drive till warmed up. Drive home and park it and let it idle full the coolant temp gets high. Once the coolant gets to 220, the clutch should lock up. If it doesn't, you either have a programming or fan clutch problem. If it doesn't throw an error code (it may not turn the check engine light on), it's a programming or sensor problem. The error code will be for fab speed not matching the fan speed demanded.

After the coolant gets to 220 and the fan clutch does not turn on, spray water through the radiator with a garden hose. If the coolant temp quickly drops, you have good coolant flow (good water pump). My guess is you have a fan clutch problem.

Now, onto the retorquing of the TTY bolts. Background: PhD in structural engineering with a good knowledge of materials. Retorquing bolts can theoretically work. In short, because the yield curve is not flat, you can increase the force on head bolts by restoring ..... to a point.

Yield is not a hard number or stress that you can stretch the bolts to and then it just keeps stretching without holding more force. There is yield stress the ultimate (or failure) stress. The ultimate stress is 10% to 50% higher than the yield stress depending on the metallurgy ( how much carbon, manganese, etc in the steel) and how quickly the bolts cool. If you will remember, quenching steel increases it's strength but also makes it brittle. Brittle steel exhibits less strength gain after yield.

So, you can increase the load by retorquing. It's just that the bolt's rate of elongation when going from yield to ultimate is higher that as it is loaded from zero to yield. Tiny increases should be achievable.

So, let's say the yield stress is 110 ksi when the bolts are initially torqued. Subsequent torquing will stretch the bolts more, but the stress on the bolt can go up to 130 ksi, thus increasing the clamping force. This should work great until the point the bolt starts necking down (decreasing the area) enough to result in less clamping force even though the stress on the bolt is higher (force equals stress times area). Again, how much you can stretch a bolt beyond yield depends on metallurgy and rate of cooling (quenching or tempering) of the bolt. Typically, the higher strength the steel, the less you can stretch it beyond the yield without failing the bolt.

Thus, it can be done and I'm tempted to try it with my TTY bolts. It must be done very carefully.

I'm putting myself to sleep with all this, so back to your regularly scheduled program.

 

This is great info..
Let me add fomoco updated the process by adding a 3rd 90* yeild. How much is left beyond that?
At what point does tensil strength of the block and threads come into play or the strength of the rocker boxes ability to handle the additional load? At what point does the change in yeild effect the bolts ability to deal with the heat expansion of the items being clamped?

 

Reps added for good info btw

 

I think your last questionis the most important. I think it's the magic question. No amount of theory could answer it. It'll take a statistically significant number of failures to answer it.

 

From a reliable source up top, the reason head studs aren't endorsed officially on this engine by the higher ups at Navistar is due to the engine block's ability to withstand the added stress on the threads comes into question. That being said, I haven't personally come across such an issue on any engine I have wrenched on thus far with studs already installed (and I have had my share needing to go in for round #2 due to using Black Onyx gaskets the first go around).