Guessing Game!

[rustyk]

My Peninsular AMG 6.5L TD has begun to be cranky when the engine is pushed; the issue is coolant temp. I used to be able to horse it (15 psi boost, EGT settled in at around 850-950 °F), and coolant temps rarely exceeded 205°F. On my way back from WV, coursing through the montains, coolant temp wanted to go to around 220°F. Easing on Down the Road (very low power output), sees the temps droppng to thermostat minimums (180°F)

I have suspicions, and will check out two of them in the next couple of days. However, here's a chance to second-guess me.

If you're right, there is no prize, only my congrats. If you're wrong, there is also no penalty.

Anyway, there are two check-first possibilities.. Guess them, and you're in line for the Grand Prize, which is: Nothing! :D

Seriously, I intend this as an exercise for those members who'd like some experience in diagnosing issues. This one is fairly straight forward...

[Hubert]

Its really always a guessing game for the first few posts unless you write a book about conditions and what nots. And its process of elmination either someone pegs it or asks the right question which leads to the answer.

Ok I start with my first guess. Partially stuck or sticky thermostat(s). As in one is stuck and other only partically opens but closes ok.

[JohnC]

It's July. Clean the June bugs out of the radiator...

[rustyk]

Hubert has ID'd my second item.

More on this issue is below:

Situation:

Background: I got StaRV II 1/06. Shortly after getting it, I flushed the cooling system and installed DexCool 50-50% with distilled water. Dual 195°F thermostats and a Hi-Flow water pump were installed a few months later. The lower radiator hose was replaced with one from NAPA, although the one in place looked fine and felt limber. The NAPA hose has internal springs to prevent collapse at the bend, where the original was wire reinforced (bonded into the hose) its entire length.

In December '06, I installed a new engine, which also included the hi-flow pump and dual thermostats (180°F). The transmission still uses the radiator to cool it, but I installed a new external oil cooler with fan. New 50-50 DexCool was installed.

The tranny was rebuilt with heavy-duty components in April '08. A 2,200 mile round trip to NY produced none of the current symptoms, although ambient temps were typically 75-80°F.

Until recently, I could climb the 6%, 5-mile hill west of Chattanooga on I-29 with water temp never rising above 205°F, even in 95°F ambient. Accelerating onto the Interstates, the temp gage stayed on the minimum reading.

Current Issue: I first noticed temp going to 215°F (well within safe limits) climbing 8% hills in WV, with outside air at 82°F, but this persisted in 5-6% hills later. Accleration onto highways sees the temp gage climb also, sometimes approaching 205°F before I can back off having reached cruising speed. In all cases the temp is sluggish going back to the "normal" reading (compared to before), but it eventually does. Boost and EGT appear to respond normally.

[simon]

tranny overheating?

what is with the dexcool??? you mentioned that twice

[cowboy4123]

I have the same prob with my truck. dual 180 thermo upgrades and hi flow pump with 21 inch fan... I can't figure it out to make it go on purpose but occasionally if the truck wants go over 210, it will, and quick! Soon as I get some down hill and let off the accelerator it goes right down to 180...... I have a new radiator i jsut bought, gotta install it this weekend, and a factory aux fan (don't know how i'm gonna make it kick automatically on?).......


What the heck are the chances of getting sticky thermostats? I had to climb a hill a 230 once again @ 15 mph..... o well.............hope this radiator does the trick, I'm tired of trying to fix this overheating crap.

[Robyn]

Fan clutch not coupling up when it should or the radiator has finally reached a point that it cant disipate the heat through the tubes to the fins where the airflow can carry it away.

My DaHooooley will heat to 230 before the fan really hooks up and then the temp plummets to 180F and then it starts over.
My radiator is the factory one and Im sure that a portion of the lower tubes are silted in with crap.

This process is slow and just creeps up until the ability of the radiator to eliminate heat reaches and impass.
Good idea TO CHECK THE STATS though just because.

I have seen some 6.5 rigs that will top out at 240F before the fan will come on. Very well clogged radiator will do just that.

The radiator in these rigs has very little extra as far as the ability to disipate heat and when that small margin is gone then the issues start showing up at least in hot weather.

Best

Robyn

[rustyk]

Well it ain't the dog you see that bites you on the a$$ - it's the one sneaking around behind. It wasn't the cooling system at all; during my crawl-around I discovered the real problem.

I had to get towed out of a muddy field 7/1; apparently the muffler dragged, and pulled an exhaust joint between the turbo and muffler, apart, so a portion of the exhaust gases were being blown into the radiator.

Since mine's a pusher, there is no fan clutch; the radiator is approximately 2.5x the size on pickups, and the fan is huge - never measureed it, but I'd guess 25", five blade.

Dexcool is the proprietary name for a coolant originally formulated (IIRC) by Texaco. It has slightly better wetting properties and a longer service life than ethylene glycol (5/50, but I intend to change every three years).

The potential issue no one mentioned is a collapsing lower radiator (suction) hose...mine's good, BTW.

[Bnave95]

I had to get towed out of a muddy field 7/1; apparently the muffler dragged, and pulled an exhaust joint between the turbo and muffler, apart, so a portion of the exhaust gases were being blown into the radiator.

Just what I was going to ask you in the first place :D