Over-cooling ???

[HogHeaven08]

Hello all, I did do a search with over-cooling and running too cool first, lol, with no results..
I put a new 506 longblock in my 1993 K2500 in 2014 and went with hi-flow W/P, D/T crossover upgrade and spankin new recore (kept my orig brass tanks :D) From day 1 this engine will not go over 60C summer or winter unless it is working... About 3 months after break-in I pulled a fully grossed 8,000LB GVWR trailer up a long 6% grade in Alberta and wow, my clutch fan kicked in for the first time, t-stats opened at abt 90C as they should.(commuting only with truck until then).
Made a 5000km trip pulling 5 ton GVWR 28' cargo trailer with 9600lbs gross on it across Canada shortly after and everything worked as it should and was very impressed for 200-ish hp and my 1st diesel pickup.
Hope ya's are still with me, lol, wanted to give some background on this issue...
I'm sure there are others who have same cooling system set-up, as this site is where I learned of it, and maybe ya'll can throw in your 2c worth if having same issue...If not does anyone know if this is normal for this cooling syst setup, and will there be any long term complications (combustion chamber) from not getting up to operating temp??? Thanks all in advance, and huge thanks to TDP admin, members, and the wealth of info on here!!! I surely would have cooked my Turbo on the 5000km trip without reading up on EGT's and installing pyro!!!

[Robyn]

What T stats are in the water outlet housing ???? 195F is the normal for these engines.....

I have never seen a 6.5 run too cool !!!!

If you are going by the dash gauge for engine temp....????

These can be off quite a bit....depending.?????

Try replacing the sending unit for the gauge....

[JohnC]

I had the same setup in my '93 (standard transmission) and it often ran cool in the winter without a load. I replaced the (single) thermostat and there was no difference. I suspected back then that it was at least partially because there was no cooling load associated with the transmission. Fortunately, also, I didn't have any overheating problems even when towing a loaded horse trailer in the summer. I had a 3.42 rear axle, so OD was out sometimes, but the mileage unloaded as impressive.

[HogHeaven08]

Thanks Robyn, 195 Robert Shaws...But why would the gauge move above 60C when I'm pulling a load??? Since the 5000 KM trip I mentioned in which I said everything "worked as it should", I should have said gauge hovered around 90-100C (195-212 F) with fan clutch engaging periodically depending on grade. I have done a couple 300 km trips pulling a 6000lb carhauler with some good long climbs since the 5000 km trip, and gauge will get to 90-ish C and fan clutch engages, so that tells me the gauge and sending unit are working...I did remove the fan and clutch assy once, keeping the pulley on with nuts on the studs when ambient temp was around 32F to get more heat from heater and did get the temp up to 80C (176F) after 15 mins of idling, short drive home 3 miles brought temp back down and re-installed.... (didn't want to risk overheating forgetting it was idling, lol). At 0 F here in winter, even with rad fully covered with cardboard and winter front on grille, can't get gauge over 60C...3/4 of a cord of hardwood firewood on 12 mile trip will get the gauge a tick over 60C... Should also mention I put on brand new HD fan clutch at engine install and noticed fan doesn't freewheel as easy as normal duty fan and was told by NAPA parts-man this is normal for HD clutch...Could it be the fan is still pulling too much air and keeping engine cooler just by convection??? (The clutch is not engaged when cold as you can really hear it roar when it engages around 100C at 60mph when I am working it)...Would really like to resolve this issue as it would be nice to get more heat in winter plus the unknown consequences of running truck below normal op temps all the time...Tks again for any and all input...Could be a non-issue soon and become a lawn ornament anyway, with diesel prices here now at $1.95/L!!! that's only $240.00 from empty, lol.

[DmaxMaverick]

How many miles/km on the timing set? Chain or gear drive?

If everything is relatively fresh (not worn out), and you have instrumentation (boost/EGT gages), too cool can mean you have room for some timing advance. What does the rattle sound like? Lively and sharp, or flat, dull and boring?

[56pan]

Could it be your temp. gauge is inaccurate_and_you've got leaves/trash on the heater core? How's the airflow with the fan on high? You've got the same cooling upgrades as my '93 2500 and it always heats the cab well.

[HogHeaven08]

Hmmm, were your temps similar to mine? 60C (140F) And only in winter?

[JohnC]

Now that you mention it, I recall I did use a winter front, too.

[HogHeaven08]

Chain drive, about 30,000KM 18,000 miles since install...all internals brand new at install, new Stanadyne pump and Bosch injectors and glow plugs as well..Timing was set at diesel shop shortly after install. EGT's never leave yellow zone when unloaded, boost at max load around 5-7...Rattle seems lively and sharp, just as when set..Starts quickly hot or cold summer and winter(always with block heater and oil pan heater). Could it be time for a little timing tweak after only 18,000 miles? Hope not, could be a real chore finding a shop here in E Canada that works on dino mech inj pumps, lol.


How many miles/km on the timing set? Chain or gear drive?

If everything is relatively fresh (not worn out), and you have instrumentation (boost/EGT gages), too cool can mean you have room for some timing advance. What does the rattle sound like? Lively and sharp, or flat, dull and boring?

[HogHeaven08]

You don't recall what temp we are talking about JohnC???


Now that you mention it, I recall I did use a winter front, too.

[HogHeaven08]

Could it be your temp. gauge is inaccurate_and_you've got leaves/trash on the heater core? How's the airflow with the fan on high? You've got the same cooling upgrades as my '93 2500 and it always heats the cab well.

I wonder if gauge is outta whack at lower temps??? Airflow is good, had heater box apart a couple years ago to check flow and removed minimal debris in there, not enough to be of concern.. Forgot I had an IR thermometer!!! , haven't used it since the move, going to try and find it and take some readings, tks 56pan!

[DmaxMaverick]

18K miles on the timing set is of no consequence.

If your fan clutch engaged about where you think it should have, according to the temp gage, the gage is as accurate as any GM gage, and the thermostat(s) are opening as they should. The fan clutch is controlled by the thermostat(s).

If your cooling system is healthy and working properly, it should be making (showing) heat. If it isn't, either the thermostats aren't fully closing, or combustion is too cold. If this is the same year round, then I suggest working on improving the engine's efficiency. Cold combustion is inefficient, wasted fuel.

Start by verifying the HPCA (Housing Pressure Cold Advance) is functioning as it should. Immediately following a cold start, remove the rear electrical connector on the IP (green wire, IIRC). This will disable the cold start advance. On a cold engine, you should notice the change immediately, with the combustion flattening out (less rattle), and perhaps some white smoke.

Any adjustment results should be noted on a warm engine, with the HPCA automatically disabled.

OEM/book timing is very conservative (retarded). If you can turn a wrench, you can adjust the timing (three hex nuts, at the back of the flange). Having a shop check or adjust your timing will set the OEM handicap, unless you ask for a specific advance. Look at the timing cover where the IP mounts. There should be scribe marks, one on the pump flange, and one on the timing cover. If they line up, the shop either didn't "time" the pump (simply aligned the scribes), or they were miraculously correct with OEM timing, which happens, but very rarely. If you don't find scribe marks, make them as a beginning reference, or if there are scribes that are not aligned, make separate scribes as your beginning reference. I've found that timing by ear and telemetry (EGT/MPG/Power/ECT) is much more accurate than the best timing equipment. Rotating the pump in the same direction as engine rotation will advance the timing (pump turns opposite the engine). 0.5mm rotation (departure of scribe marks) at a time is a safe increment, although you may not notice change until 1mm or more if it's set to OEM timing. Simply loosen the flange nuts slightly, rotate the pump, then tighten the nuts. I set timing on a running engine, but I DO NOT recommend that for all but experienced mechanics. It's much faster, with immediate results, but there is risk (you're reaching over a running engine, after all). It's better for most folks to make adjustments on a still engine, then start/run to note the result. If at any time you don't feel right with your result, you can always return the timing back to the (your) original reference marks, or closer to it.

[JohnC]

You don't recall what temp we are talking about JohnC???

I'm not sure I understand the question. It was over 20 year ago. All I remember is it would run very cool on cold days unless you were really loading it up. Just driving around town the heat from the heater was marginal at best. My '95 with the automatic always warmed up to the expected temperature.

[More Power]

Drive it around a bit (engine well up to operating temp), then open the hood and feel the top radiator hose. It should feel really warm.

If the hose feels really warm, the t-stat is opening - slightly, to maintain temp. If the hose is a lot cooler than the t-stat housing, somehow the t-stat isn't opening. The engine should overheat if the t-stat isn't opening (stuck closed).

If the top rad hose feels more or less the same temp as the thermostat housing all the time - even during warmup, the t-stat is stuck open.

Is the t-stat installed correctly? I know it's a dumb question, but it happens.