Hello everyone,
I was driving the bus back from LA to San Diego last week when all of a sudden the coolant temp spiked as I was climbing a hill. I immediately pulled over and the temp quickly returned to normal. I was then able to carefully drive the bus another couple miles to my house with some fluctuation in temp coinciding with slight inclines or declines in grades.
Question - what's the most likely culprit? I was thinking water pump but I had the water pump rebuilt approx 4,000 miles ago (although it has been approx 10 years since the rebuild). There is also no coolant leaking from the pump (or anywhere else). My next thought is thermostat, not sure if my symptoms match a thermostat issue?
A clogged radiator would also match these symptoms I believe, but I'm not sure how to tell if that's the issue?
Any insight would be appreciated. I had driven 100+ miles that day with no issues before the sudden spike.
Unfortunately, with the information given there are many possibilities. I would start with the easiest first. Do the radiators need to be cleaned? Is the fan belt slipping? Are you keeping the rpm's in the right range? Is your air intake in good shape (I once had a heat problem that was caused by the engine air intake hose collapsing under load. It would look fine when the engine was idling though)? Is your temp sensor accurate? etc.
- RPM's = normal
- Fan belt does not appear to be slipping
- temp gauge was just replaced and sender appears to be operating correctly.
What I haven't done is try to clean the radiator itself, I'm going to try that and see what happens. Maybe some road grime is not allowing air to cool the fins?
Its all about engine loading,, when climbing, speed is not a priority,, drop a gear AS NEEDED to keep the fan speed up and UNLOAD the engine... The heavier the load on the engine the more heat it will make.. Evan if selecting low gear is needed to control heat, it's better than destroying equipment. ( Have you ever wondered why 18 wheelers have so many gears.??? ?)
A hand-held IR thermometer (yes, I know they're not totally accurate) is useful to check radiator and engine block temperatures. One of several reasons I completely rebuilt my entire cooling system a few years was because my IR thermometer showed that my radiator had a cold spot: the tubes there were blocked by crud in the top tank. I also find a turbo boost gauge to be useful for controlling engine temps - when climbing long grades in hot weather I manually downshift to third on a 3/4 throttle, keep the revs at about 1900 RPM and the boost at about 18 PSI. If I let the boost get higher the temperature will immediately rise, so for my bus that's evidently the sweet spot for climbing.
John
After you correct the problem, consider a mister system to avoid damage to engine on one of those 100 plus degree days on a grade that seems to last forever.
Thanks for the replies. The bus generally runs on the cooler side, approx 170 or so, which was the case 95% of the way home with many 6% grades. That is until the last hill it had to climb before my house where something gave out. I have an IR thermometer and tomorrow will see if there are any large temp differences and report back.
Follow up question - is flushing the radiator something a novice like myself can tackle, or is this best left to a professional mechanic? If it's something I can tackle with a good youtube video or something I am game to try.
Respectfully ...
We have not yet determined what constitutes "Normal RPM". Two stroke Detroits MUST be run against the governor going up long steep hills. This means 2000-2200 rpm. Even with partial throttle. Sometimes an automatic will not allow this. The other answers have already covered it. Before anything else check to make sure the radiator(s) is/are full of water.
Quote from: HB of CJ on June 09, 2019, 01:53:31 PM
Respectfully ...
We have not yet determined what constitutes "Normal RPM". Two stroke Detroits MUST be run against the governor going up long steep hills. This means 2000-2200 rpm. Even with partial throttle. Sometimes an automatic will not allow this. The other answers have already covered it. Before anything else check to make sure the radiator(s) is/are full of water.
I should have been more specific - this was not a long steep hill, it was probably around 6% grade and at most 1/2 mile long. The outside temp was in the mid 60's. I went up considerably longer and some steeper hills earlier in the drive with no overheating issues whatsoever.
I am not sure what you mean by "run up against the governor"?
Running the 2 stroke Detroit Diesel "Against The Governor" means putting your foot to the floor and letting the engine run as fast as it will go. 6v92T Detroits can be governed anywhere from 1800 to 2400 rpm. Running your engine that fast going up a short steep grade will not hurt it.
The older 71 N series Detroits were designed to run against the governor in heavy truck service. Very under powered. I figure the DD 92 series would be about the same except for the big MUI 500 hp 8v92TA which could run at about 1500 going down the road. Hills? Flat out wide open.
Hope this helps. MUI means no computers. Mechanical Unit Injectors. All mechanical. DD means computer controls. N means very old with no turbo charging. Is your Bus Conversion low on radiator water? Other answers pretty much cover what your over heating problem may be.
Respectfully.
Takes very little dirt and grime in the radiators on the C with the 2 side mounted radiators to make it run warm,clean the fins and check the seal around each radiator,they have a habit of collecting dirt at the bottom 4 inches if you cannot see a light through one it is dirty
Thanks guys, I'm going to clean the radiator tomorrow and see if that helps.
As far as the thermostat possibly being the issue - since the temp quickly comes back down to normal when there is not a heavy load on the engine does that make this being a thermostat failure less likely? My understanding is if it's a bad thermostat the temp will climb quickly but generally stays high.
I have yet to read what the high temperature "spike" was in degrees.
Quote from: Geoff on June 10, 2019, 07:04:14 AM
I have yet to read what the high temperature "spike" was in degrees.
It was darn close to 240, if not at 240. Close enough for me to immediately pull over on the 15 frwy.
Quote from: JT4SC on June 10, 2019, 09:21:00 AM
It was darn close to 240, if not at 240. Close enough for me to immediately pull over on the 15 frwy.
with the rebuilt water pump whom ever done the rebuild may not have the impeller tight on the shaft and the shaft is spinning but not the impeller happens all the time around here
Quote from: luvrbus on June 10, 2019, 10:17:45 AM
with the rebuilt water pump whom ever done the rebuild may not have the impeller tight on the shaft and the shaft is spinning but not the impeller happens all the time around here
Interesting, is that something that I can check or do I need to bring to a mechanic. There is a plate on the front of the water pump that can come off without taking the whole pump off (at least that's what it looks like to me).
Hi JT, I took my bus in to get it washed at a truck stop wash, and had the engine wash because I was trying to track down some oil leaks, and a high-pressure spray turned the valve that actuates the tightness and release for the nine foot long fan belt and it was halfway open because of the water pressure I couldn't figure out why my engine was running hotter going uphill until I stumbled upon that now I check it every time I go out, lvmci...
Clifford, how do you Check for damage from overheating, does oil analysis show that damage? Tom...
If it actually hit 240, expect engine work in the near future. You need to verify temperature gauge accuracy before replacing parts. Also verify your coolant wasn't low.
Quote from: lvmci on June 10, 2019, 03:05:28 PM
Clifford, how do you Check for damage from overheating, does oil analysis show that damage? Tom...
The oil sample will show coolant from damage by heat,the next time you come I will show you some liners and pistons what heat causes and you can check those from the inspection covers
Quote from: chessie4905 on June 10, 2019, 03:43:21 PM
If it actually hit 240, expect engine work in the near future. You need to verify temperature gauge accuracy before replacing parts. Also verify your coolant wasn't low.
If the safety shut down is working it would have stopped the engine @ 215 ,@ 240 a 92 series will crack the heads 95% of the time
Analysis paralysis.
Now what does he DO?
If the coolant is staying where it belongs, you dodged a bullet.
Did we ever confirm there was/is proper coolant level in this engine? You better figure out an extremely rigid way to check the level at the same cold temp so you can measure, and you need a catch can on the overflow, or you'll freak and misdiagnose puking excess for broken engine bits...
I don't hold much stock in the temp gauge ability to accurately indicate terminal temperature, so all you know is gauge was reading higher than "normal".
Add in the ancient corroded wiring in between engine and dash gauge...
Vibration finally created a stronger path for electricity, and the shitty sender, or the shitty gauge now reads wildly wrong, instead of just a little wrong...
Sudden temp returning to "normal" suggests needle travel is not linear to temp change...
So you gauge system is totally bullshit unless proven otherwise.
Need 2 people, one to shoot the IR gun down through the floor engine access and the other to drive the coach.
The stock coach heating pipes are readily available down thru there to aim the IR gun at.
There has to be flow to get current engine temps, so open the driver's heat/defrost valve so the juice flows, and go for a drive.
Caution, the one down the back might be well advised to wear a monogoggle, windy and dusty back there...
Holler back and forth as to readings.
Find that big hill and prove that gauge has caused all sorts of unnecessary heart ache...
I am rooting for you!
Happy coaching!
Buswarrior
Quote from: luvrbus on June 10, 2019, 08:35:21 PM
If the safety shut down is working it would have stopped the engine @ 215 ,@ 240 a 92 series will crack the heads 95% of the time
Does DDEC also shut down at 215 degrees? I know there's some power reduction before actual shutdown, but I've not been able to find the shutdown temps in my DDEC manuals.
Thanks, John
Update - I decided now wasn't a good time to try to figure out how to do this myself so I took it to a diesel mechanic in town. It's looking like it's the water pump that is the main issue, he said the bearing broke so it's just spinning in place and not grabbing any water/coolant. They are also going to replace the thermostats While they are in there.
My question for you guys is I just had the water pump rebuilt about 4,000 miles ago, however that was about 10 years ago as well. Does the fact that the water pump went out again lead anyone to believe there is some other issue going on which is causing the water pump to fail prematurely? L
Quote from: JT4SC on June 13, 2019, 11:08:05 AM
Update - I decided now wasn't a good time to try to figure out how to do this myself so I took it to a diesel mechanic in town. It's looking like it's the water pump that is the main issue, he said the bearing broke so it's just spinning in place and not grabbing any water/coolant. They are also going to replace the thermostats While they are in there.
My question for you guys is I just had the water pump rebuilt about 4,000 miles ago, however that was about 10 years ago as well. Does the fact that the water pump went out again lead anyone to believe there is some other issue going on which is causing the water pump to fail prematurely? L
Water pump was 'rebuilt' - what did they actually do ten years ago? Did they just replace seals and call it a day or did they replace everything - bearings, impeller, etc.?
I'm no expert, but isn't this one of those things that does better with use than non-use? Only 4000 miles in 10 years is not much run time, and for coolant to provide protection it needs to circulate. What's your coolant look like?
Quote from: JT4SC on June 13, 2019, 11:08:05 AM
Update - I decided now wasn't a good time to try to figure out how to do this myself so I took it to a diesel mechanic in town. It's looking like it's the water pump that is the main issue, he said the bearing broke so it's just spinning in place and not grabbing any water/coolant. They are also going to replace the thermostats While they are in there.
My question for you guys is I just had the water pump rebuilt about 4,000 miles ago, however that was about 10 years ago as well. Does the fact that the water pump went out again lead anyone to believe there is some other issue going on which is causing the water pump to fail prematurely? L
People do crapy jobs rebuilding water pumps because most do not want to remove and replace the bearing because the gear needs to be pulled and the back lash on the drive gear needs to be redone,have your guy set the back lash on the gears or it will fail again
Quote from: luvrbus on June 13, 2019, 01:51:21 PM
People do crapy jobs rebuilding water pumps because most do not want to remove and replace the bearing because the gear needs to be pulled and the back lash on the drive gear needs to be redone,have your guy set the back lash on the gears or it will fail again
Sounds good, will do!
Richard, we got hit real hard in the recession and there was a couple years we just couldn't use the bus much at all. I'm thankful we've been able to use it about every month for the last couple years now.
Quote from: JT4SC on June 13, 2019, 04:51:31 PM
Sounds good, will do!
Richard, we got hit real hard in the recession and there was a couple years we just couldn't use the bus much at all. I'm thankful we've been able to use it about every month for the last couple years now.
I get it - not trying to be critical of your reasons for the low mileage. Glad you are able to get out and enjoy it more now.
A (frustrating) update: the mechanic just called me saying they located a new water pump and thermostats but now need to take the entire radiator out to change these parts. I haven't agreed to any repairs at this point, and taking out the radiator for this repair doesn't sound right to me, but I wanted to confirm that with you guys before I look for a new shop or figure out how to do the repair myself.
What coach is this engine in?
Quote from: Van on June 17, 2019, 04:02:30 PM
What coach is this engine in?
1993 MCI 102C3. Radiators are up high in this bus and nowhere close to the water pump.
Hmmm. Might be time for an alternate plan. watch your six!
Quote from: Van on June 17, 2019, 04:28:32 PM
Hmmm. Might be time for an alternate plan. watch your six!
They quoted $3,700. To fix a water pump and replace thermostats. I about fainted. :)
With that said does anyone know a trustworthy mechanic in San Diego with working knowledge of these older 2 stroke DD's? I used to go to valley power but they closed their shop in SD.
$3700.00 is the we don't want to fool with it quote ,5 hours @140.00,2 tstats's with gaskets and seals $125.00,coolant $250.00,new hoses and clamps $100.00 tops 1 rebuilt exchange water pump from DD $650.00 maybe throw in a oil change for $250.00,$2000.00 is overpriced
Quote from: luvrbus on June 17, 2019, 04:58:32 PM
$3700.00 is the we don't want to fool with it quote ,5 hours @140.00,2 tstats's with gaskets and seals $125.00,coolant $250.00,new hoses and clamps $100.00 tops 1 rebuilt exchange water pump from DD $650.00 maybe throw in a oil change for $250.00,$2000.00 is overpriced
Yeah, most likely right. But to confirm there is no need to remove the radiator right?
Quote from: JT4SC on June 17, 2019, 05:08:43 PM
Yeah, most likely right. But to confirm there is no need to remove the radiator right?
NO unless he was planning on sending the radiators out to be cleaned and rodded
Quote from: luvrbus on June 17, 2019, 05:14:11 PM
NO unless he was planning on sending the radiators out to be cleaned and rodded
Thanks brother I appreciate it.