Weird heat issue

[Geom]

At least it's weird to me...

We've ventured forth into the mountains (after spending far too many months in relative lowlands). Making our way to CO, I've noticed an odd heat issue.
I've been monitoring the engine temps pretty closely on the bus and usually she runs about 185-190ish -when working moderately, climbing to shy of 195 when working hard (climbing a 6% grade on an 80 degree day for example).

Now that we've started this climb (somewhere near eastern KS), I've noticed that we've been running consistently at just shy of 190, a lot. Granted the days have been hotter (86 degree day for example), but it seems to be doing it even on 75 degree days -just not quite as often.

The temps seem to be directly related to speed, almost entirely.
If I slow down, the temps cool way down and I actually get to 180ish territory.
So at about 60 mph I'm at 190, but going even to 63,64 etc is enough to cause it to creep closer to 195 territory.
As we've been driving around, we've been pulling over a few times in a trip, both out of typical "trip" type stuff, along with trying to keep things cooler.
The second we pull into a rest stop or even pull over at an off ramp, the temps plummet.

We kept managing things this way and have actually done quite well. We covered a lot of terrain in a couple of days driving.
No complaints other than the temp issue. Although I have noticed an increase in oil consumption. Along with a few wet spots at rest stops. Nothing too terribly outrageous, I don't think.
Oil is around a quart every 200-250 miles. Sometimes more, sometimes less.
Overflow/blowby oil container thing is usually mostly empty.
I dump it occasionally and get maybe a solid trickle for a few seconds.
But that engine is dirty! As it does leak oil, a lot I think. It's unfortunate, but it is, and were managing. One "trick" to reducing oil use is by keeping the oil half-way between full and low (sometimes lower). That seems to significantly reduce usage and overall ... Splatter.

Today, however something new happened that has me more concerned. We'd made it into Denver and were just a few miles from our exit.
We were climbing what seemed like a fairly small hill (compared to some of the more formidable ones so far), and the temps climbed..
On to 195 in a hurry, then past 195...
Hmm, ok it's done this rarely before, even on this trip, but usually something like 196-197.
And it cools off right after its "hard workout" is done and comes back down pretty well.
This just kept going and now I was becoming concerned.

Navigating the serpentine uphill road, while trying to find a "suitable" exit and place to stop, and trying to control the temps, was certainly a harrowing experience.
I slowed way down, and down shifted to second.
I was pulling about 57-58mph and holding decent temps at first.
The grade did change upward, although not seemingly that much. But after shifting to second, I was doing about 45mph and about 1900ish rpm, and the temps just kept climbing.
Outside temps were low to mid 70s.
Fortunately, our intended exit was on a slow downhill.
I was able to back off of the throttle, pretty much entirely.
The temps started to come down quickly and we made the exit and navigated those serpentine and climbing roads, to our campsite, without much issue -albeit at much lower speeds of 15-20mph.

So that's what happened.
The temp ranges, overall all are not new. It's been pretty much this way since we bought it.
It's never really gone this far to the "wrong" side of the temps (195) before.
I don't think anything too terrible has happened and it eventually cooled right down after it got probably to 200-201.

What I want to know is, is this normal? Am I doing something wrong that I should be changing? Why does it seem to be so... temperamental?
And most importantly, why this new behavior?

I check coolant level fairly regularly -every trip.
And the surge tank is always at the right level.
We had the coolant (and a bunch of other fluids) changed at our last maintenance visit (In TN).
Used a ~55/45 mix of coolant and distilled water.
There are auxiliary cooling fans on the engine.
One is attached blowing air toward the radiator, and on into the engine bay.
Another is on the opposite side sucking air away from the transmission bell housing.
Another draws air from the top of the engine bay toward the bottom with 12v duct/fans (which move an impressive amount of air out).
So I would think there's ample "fresh air" movement happening.
Although turning the fans on/off doesn't seem to make that much of a difference when it's "working hard" -albeit some.
It certainly cools things way faster when we slow down or take an off ramp.

The transmission temps, on the other hand seem ridiculously low (below 140), often below gauge range. Hard to tell if that's sensor error or real. Sometimes it likes to climb to 160ish, when "working hard". But that is not an often occurrence, even at high rpm, or pulling a grade, etc.
The sender is attached to an oil return line and not actually *in* the transmission directly. That return line comes from an external cooler.
There is a secondary oil cooler/radiator attached to the main radiator (over the main radiator). 
That has the inbound aux fan blowing on it, then onto the main radiator underneath it, and then on toward the block.
Transmission oil is routed through that secondary cooler and back to the transmission housing.

Anyway, I'm going to dig into this some more tomorrow, -Checking different fluid levels, etc.
I suspect the coolant will be fine, and the oil might be closer to low; but we'll see.

Your thoughts, ideas, etc on this are appreciated, as always.
Thanks
George

[niles500]

Check to see if your Tstats are functioning properly (fully opening) what type of coolant are you using? You are using straight 40 wt. Cf-2 oil? With all the auxiliary fans and coolers you have it is an indication that your bus has had cooling problems for quite some time - HTH

[Runcutter]

Do you, by any chance, have a "mud flap" under the rear bumper?  GM put flaps behind the rear axle, not under the bumper, to help create a low pressure area for heat to exhaust.  Some folks put a flap under the bumper to keep their towed vehicle clean, but that traps hot air.

Arthur

[Dave5Cs]

Hi George, are the gauges working correctly and does the one at the dash the same as the one in the engine bay as far as readings? Did you use a final charge coolant or just regular antifreeze? When going up grades do you down shift and keep the revs up or does it lug because that would let the heat raise. I always watch the tailpipe exhaust when climbing and if it is black smoke coming out then I shift from 3rd down to 2nd or even 1st and back off on the peddle, because it just ads fuel and heat with no real increase in speed. That will kill an engine faster than anything.
The oil problem you said that you lose less when between marks not fully full. You might check the marks on your stick. It should be about 1 inch below the top of the pan to engine block line. If you have to much oil in it the engine wants to get rid of it and throws it out. If your marks are off then you could just be refilling the overage amount.
Used to live in Colorado Springs for 10 years. Lots to see in the state. If you get up there go see Garden of the Gods, and Manitou springs.
Dave5Cs

[HB of CJ]

Automatic or manual?  You indicated very low trans temps of 145F?  If an automatic then there is your clue.  Consider bad senders or gages?  Sender locations?  Wiring?  Your auto tranny should be cooking right along with the engine and usually take longer to cool.

[TomC]

Your temps are not too high.

[oltrunt]

I don';t really know very much but, on my MCI 8V92, I kept having the engine shut down for "over temp" and went nuts trying to figure it out.  It turned out to be that the nut securing the water pump impeller had loosened and the impeller wasn't turning-- the bus was cooling by "convection".  Jack

[luvrbus]

You muffler and air cleaner system can cause a 2 stroke to run warm,since it is a transplanted engine I would check the CFM on the exhaust and air cleaner

[Geom]

Thanks all for the ideas and suggestions.
Here's a summary of some of the questions/follow ups

The tstat appears to be working ok. It can sit and idle forever and not break a sweat (hi-idle). Even after running a bit hot it cools right down when no longer "working hard". So it seems like something is not keeping up, instead of a thermostat staying shut or open... To me anyway.
Is there ankther way to test the thermostat that I can try?

I'm using "conventional" full strength "heavy duty" ethelene glycol (whatever heavy duty means). But it's the stuff my mechanic uses in everything, Detroit included. It's diluted to a 55/45 mix with water.

Use delo 100 40wt oil, and have since we got it.

I do have the mud-flap(s) installed ahead of the engine bay and not under the bumper.

I believe the gauge (up front) is working. The one in the engine bay, however, is InOp. It's connected correctly to the probe, but never registers a temp. Never has. I've spent some time troubleshooting it in the past and haven't found out why. It's directly attached but I'm not sure if there's an electrical component to it I'm missing. If there is, I don't see it.

I've endlessly continued to try and cipher through the mystic runes of the sages, on what "not lugging a Detroit" actually means exactly. Along with "drive it like you stole it" or "drive it like you're mad at it", "how to push a screaming jimmy", etc, etc.
So I've settled on this. At no point does it ever smoke when I apply throttle, no matter how much I ask of it, except when starting from a dead stop. Then it smokes for a healthy puff and then all is clear. Otherwise I can mash the pedal and always get more power.
So what I've been using is speed to rpm. If I mash the pedal and I'm not able to maintain 57-58 with the rpm creeping below 1500, I slow down and force it into second. It will not stay in second and will up shift automatically at about 58-59. So when the situation calls for it, I just keep it around 54-55. That gets the rpm to about 1900-1950. Sometimes that seems to help cool it down, but surprisingly sometimes staying in 3rd and having it "pull" that tiny just long enough to be annoying little hill, doing 60-61 in 3rd; actually works better.
It just really depends on the length of the grade and what she feels like doing at that moment.
If that makes sense.
Bigger more obvious hills I always downshift and keep the speed ~55 (or slower depending on how steep, 45).

But generally I maintain about 1600-1800 rpm as long as she's got power to provide.

We looked into the oil capacity thing and I think the stick is right. We put in about 6 gallons of oil (and then maybe another .5 gallons) and that was enough for the filter. That shows the stick at half-way between. Putting more than halfway really does seem to make it spit (more) though. But regardless it's always got oil all around it.

It is a an automatic, v730. Sometimes the trans temp gauge will "hop" when it's working really hard. But usually it's just silent. It's mounted directly into the return line coming back from that cooler, and I wonder what the temp of that is at that point and whether it is a location error or gauge error. A new sender (and subsequent replacement effort thereof) are on "the list". I checked the wiring and it seems good and solid. I can directly tap the sender wire to ground and actuate the gauge up front just fine.

I'm intrigued by the water pump possibility. That might explain why it behaves so well under moderate load, but not heavier loads. I don't know how I'd test that. I do know that the water pump is capable of rotating the water through the front defrost core without issue. I would suspect convection alone wouldn't accomplish that?? Not sure if there's another water pump test?

The muffler (and other exhaust bits) is enclosed in a (very professional looking) heat wrap blanket to keep heat out of the engine bay. I'm not sure how I can test the muffler or air cleaner (I'm not sure where that even is). Any additional guidance there is appreciated on how to do so and what I'm looking for when I check it.


I did check the coolant and it is exactly where it has been since we refilled it weeks ago.
The oil was a little close to the low side of the stick. I suspect a 1/2qt will get it to the midway point again. Maybe a bit more than that.

I'll continue looking and take some of the suggestions above and do some more digging.

I also plan on moving that intake electric fan up a bit more and get it blowing more directly on the main radiator and not so much on the secondary transmission cooler. It seems like the trans is getting getting plenty of cooling with the external oil cooler along with the usual heat-exchanger cooler inside the engine bay...
But there's not currently a way to be certain with the gauge readings so far.

Thanks again,
George

[eagle19952]

if you do not have an operational over-temp shut down... you will probably regret it soon or some day... if you do not..why not ?

you will definitely sleep better and type less if you do

Thanks all for the ideas and suggestions.
Here's a summary of some of the questions/follow ups

The tstat appears to be working ok. It can sit and idle forever and not break a sweat (hi-idle). Even after running a bit hot it cools right down when no longer "working hard". So it seems like something is not keeping up, instead of a thermostat staying shut or open... To me anyway.
Is there ankther way to test the thermostat that I can try?

I'm using "conventional" full strength "heavy duty" ethelene glycol (whatever heavy duty means). But it's the stuff my mechanic uses in everything, Detroit included. It's diluted to a 55/45 mix with water.

Use delo 100 40wt oil, and have since we got it.

I do have the mud-flap(s) installed ahead of the engine bay and not under the bumper.

I believe the gauge (up front) is working. The one in the engine bay, however, is InOp. It's connected correctly to the probe, but never registers a temp. Never has. I've spent some time troubleshooting it in the past and haven't found out why. It's directly attached but I'm not sure if there's an electrical component to it I'm missing. If there is, I don't see it.

I've endlessly continued for try and cipher through the mystic runes of the sages, on what "not lugging a Detroit" actually means exactly. Along with "drive it like you stole it" or "drive it like you're mad at it", "how to push a screaming jimmy", etc, etc.
So I've settled on this. At no point does it ever smoke when I apply throttle, no matter how much I ask of it, except when starting from a dead stop. Then it smokes for a healthy puff and then all is clear. Otherwise I can mash the pedal and always get more power.
So what I've been using is speed to rpm. If I mash the pedal and I'm not able to maintain 57-58 with the rpm creeping below 1500, I slow down and force it into second. It will not stay in second and will up shift automatically at about 58-59. So when the situation calls for it, I just keep it around 54-55. That gets the rpm to about 1900-1950. Sometimes that seems to help cool it down, but surprisingly sometimes staying in 3rd and having it "pull" that tiny just long enough to be annoying little hill, doing 60-61 in 3rd; actually works better.
It just really depends on the length of the grade and what she feels like doing at that moment.
If that makes sense.
Bigger more obvious hills I always downshift and keep the speed ~55 (or slower depending on how steep, 45).

But generally I maintain about 1600-1800 rpm as long as she's got power to provide.

We looked into the oil capacity thing and I think the stick is right. We put in about 6 gallons of oil (and then maybe another .5 gallons) and that was enough for the filter. That shows the stick at half-way between. Putting more than halfway really does seem to make it spit (more) though. But regardless it's always got oil all around it.

It is a an automatic, v730. Sometimes the trans temp gauge will "hop" when it's working really hard. But usually it's just silent. It's mounted directly into the return line coming back from that cooler, and I wonder what the temp of that is at that point and whether it is a location error or gauge error. A new sender (and subsequent replacement effort thereof) are on "the list". I checked the wiring and it seems good and solid. I can directly tap the sender wire to ground and actuate the gauge up front just fine.

I'm intrigued by the water pump possibility. That might explain why it behaves so well under moderate load, but not heavier loads. I don't know how I'd test that. I do know that the water pump is capable of rotating the water through the front defrost core without issue. I would suspect convection alone wouldn't accomplish that?? Not sure if there's another water pump test?

The muffler (and other exhaust bits) is enclosed in a (very professional looking) heat wrap blanket to keep heat out of the engine bay. I'm not sure how I can test the muffler or air cleaner (I'm not sure where that even is). Any additional guidance there is appreciated on how to do so and what I'm looking for when I check it.


I did check the coolant and it is exactly where it has been since we refilled it weeks ago.
The oil was a little close to the low side of the stick. I suspect a 1/2qt will get it to the midway point again. Maybe a bit more than that.

I'll continue looking and take some of the suggestions above and do some more digging.

I also plan on moving that intake electric fan up a bit more and get it blowing more directly on the main radiator and not so much on the secondary transmission cooler. It seems like the trans is getting getting plenty of cooling with the external oil cooler along with the usual heat-exchanger cooler inside the engine bay...
But there's not currently a way to be certain with the gauge readings so far.

Thanks again,
George

[TomC]

When I increased my power on the 8V-71 from 300hp @ 800 torque to 375hp and 1125 torque by turbocharging, air to air intercooling, and increasing the injectors from N65 to 7G75, I had the radiator recored from 5 row straight fin to 6 row serpentine, increased the air cleaner from 6" to 7", changed the muffler to a turbo muffler, added an oil to air transmission cooler with thermostatically controlled electric fan before the normal shell cooler to take out heat that would be sent to the radiator. I still can over heat pulling a hill on over 85 degree day. I added essentially 2 misters that are drilled out to 1/16" that will bring the temp down in about 2 minutes of water. Not afraid to go anywhere now-mainly because I had almost stalled out a couple of times in the mountains-now no power worries. Good Luck, TomC

[opus]

Are you sure you have thermostats installed?

[buswarrior]

Air cleaner obstruction?

The higher you go, the harder it is to breathe, a less than clean air cleaner will raise engine temps.

Get an IR heat temp gun to confirm dash gauge. Open engine access inside, find the hot coolant pipe, shoot while underway, compare readings.

It will be noisey and windy back there with the lid open.

It is useless worrying any more, until you can be sure what the temps really are.
My MC8 shows 10 degrees rise on the dash when it's only 5 degrees rise at the engine, discovered this way.

happy coaching!
buswarrior

[Cary and Don]

I wouldn't move that fan.  If you move it it will be blowing against one side of the engine fan. The oil comes out of the transmission, past the temp sensor, to the cooler in front of the radiator, to the original cooler on the compartment wall, and then back to the transmission. The cooler on the wall will prevent the transmission from running too cool because the engine water runs through it and will warm the oil.

You need to take into consideration your altitude on these climbs. The higher you go, the harder the climb is for it and the hotter it gets. Have you used your misters when it climbs over 195 degrees?  If you get to 5000 feet you will notice a difference in the temps and power. We would flip those misters on if the temps got over 190 and we knew there was still hill to climb. Just flip them on and turn them off when the temps start to drop again. They feed from your fresh water tank.  There is a switch by the driver for the misters.

It has always spit oil if full so we kept in at half way between fill and full on the stick.

Don and Cary

[oltrunt]

Ditto on the over temp shut down!