Cummins Diesel Forum banner

Couple Issues: Cooling and Starting

2K views 26 replies 8 participants last post by  natemoses13 
#1 ·
Hello everyone, I started a thread in the Washington forum but I figured I'd post out here to see what others thought. The first issue is running to cool, I've read the thread about people running at (160) and what not but mine will barely hold 140 going down the highway! I thought it was a tstat that was stuck open so this weekend I replaced it with a Geno's tstat and its no better. On the highway the temperature plumets to 140 or even below sometimes. Ideas?

Second issue is with cold starts. The motor will fire up and idle fine then miss and die if i don't give it more throttle until it cleans up. A few seconds later it will start missing again (wont die) regain itself and be 100% perfect. I just replaced my fuel filter (Wix with less then 15k on it) today hoping that it may solve the issue. As a side note I found this while I was replacing my tstat this weekend. Its hard to see in the pictures but there is fuel around the base of the injector.

 
See less See more
1
#2 ·
Hello everyone, I started a thread in the Washington forum but I figured I'd post out here to see what others thought. The first issue is running to cool, I've read the thread about people running at (160) and what not but mine will barely hold 140 going down the highway! I thought it was a tstat that was stuck open so this weekend I replaced it with a Geno's tstat and its no better. On the highway the temperature plumets to 140 or even below sometimes. Ideas?
Well, let's see. Do you have hot heat?

If so, I'm thinking your temp sensor.

It's also possible your new t-stat is bad, though unlikely.

How's your fan clutch?

Second issue is with cold starts. The motor will fire up and idle fine then miss and die if i don't give it more throttle until it cleans up. A few seconds later it will start missing again (wont die) regain itself and be 100% perfect. I just replaced my fuel filter (Wix with less then 15k on it) today hoping that it may solve the issue. As a side note I found this while I was replacing my tstat this weekend. Its hard to see in the pictures but there is fuel around the base of the injector.

Sounds like air getting into the fuel lines somewhere. I can't see your pic.
 
#3 ·
does it ever get up to temp? like I said in your other thread, heating up to 190F, plummeting to 140F over and over is completely normal.

but if it never reaches temp, it could be the temp sensor like stated above
 
#4 ·
If by hot heat you meant in cab, no. I'd call it warm but going down the highway it might blow 65*, maybe.
Fan clutch: I was wondering about this also, my fan is always going Ive never seen or heard it shut off.

e-rok: Yeah I remember you saying that. It will only reach temp if the truck isnt moving, or in traffic. Gotta be below say 30mph. When i drive form my house to, say, tacoma which is 20miles or so. The truck will never hit 190. If it hits 160* thats a good day.

Let me try the picture again.....
http://s1117.photobucket.com/user/oct6454/media/Mobile Uploads/IMG_1256.jpg.html
 
#6 · (Edited)
illflem, i read that sticky and understand its supposed to fluctuate(Mine fluctuates around town or in traffic). The issue is that it does not fluctuate and often never reaches OT hen on the highway or when I dont hit redlights. When I cruz the highway at 60mph it'll run at around 130* never getting warmer. If thats what was meant by low temps in the sticky then I apologize for the misunderstanding, just wanted to make sure the truck isnt running to cold.
Thanks, Oliver

BTW the fuel filter seemed to fix the difficult start.
 
#7 ·
Is the next step a new temp sensor? When te truck runs down the highway for 45min and the temp just sits at 120* I get worried that it's too cool, but I don't want to put cardboard up front then have to remove it in the city. Could it e possible that my fan is stuck engaged?


Sent from AutoGuide.com Free App
 
#8 ·
Is the next step a new temp sensor? When te truck runs down the highway for 45min and the temp just sits at 120* I get worried that it's too cool, but I don't want to put cardboard up front then have to remove it in the city. Could it e possible that my fan is stuck engaged?
If the fan clutch is locked up you would hear the fan roaring at highway speeds. It wouldn't make a bit of difference it it is locked up if the thermostat is working correctly. This time of year you could completely remove the fan and be OK unless you are towing. Don't replace the temp sensor without actually checking the engine temp with an IR heat gun. It will also tell you if the thermostat is working correctly. If by "replaced it with a Geno's tstat" you mean a Gates or Stant I have heard they don't work well in a Cummins, and frankly, I'm surprised Genos carries them. To check the thermostat get the engine warm, then have someone hold it at a high idle while you check the top hose where it connects to the thermostat housing for temp. If the t-stat is working the temp will slowly rise to 180-190 on the engine side of the stat, but be cooler on the hose side. When it opens it will jump to 180-190 on the hose side, then almost immediately drop back down as the t-stat closes again. As for the heater, use the same heat gun to check the in and out hoses. If there is low flow thru the core the out hose will be a lot cooler than whatever the t-stat temp rating is, and the in hose will probably be lower as well.
 
#9 ·
Okay I'm going to look for a IR heat gun as I dont own one. The odd thing about this issue is that, the tstat I replaced had the same issue as the one I put in. What I do know is that the issue seems to be dependent on engine RPM unless its out of gear.
 
#11 ·
I was running with 100% grille coverage and had no issues with heat until my fan clutch failed. Even then, my engine still stayed under the 190 line but I noticed the transmission starting to act funny. I took out my grille inserts over the transmission cooler and the transmission symptoms went away.

The fan is a serious powerhouse and will pull as much air as it needs from under the bumper. You won't have to take any cardboard out running in town.
 
#12 ·
Games, luckily tstats are easy and very inexpensive. Just at a loss for what else could be causing it. It been this way since I bought the truck a couple years back.


Sent from AutoGuide.com Free App
 
#13 ·
Games, luckily tstats are easy and very inexpensive. Just at a loss for what else could be causing it. It been this way since I bought the truck a couple years back.
First, it is capital G, capital A, first initial, last name.

Cummins t-stats aren't "very inexpensive", so an after market one might contribute to your problem. You get what you pay for. Have you ever flushed and refilled the cooling system?
 
  • Like
Reactions: Curbo
#14 · (Edited)
My bad. Yepp, had that done less then a year ago, last May to be exact. I had studs put in last May so while they (the shop) already had the truck I asked if they would flush the cooling system as well, along with some other unrelated items.

If it helps you, today after I got back from a car show. I did a little "testing" to see if I could figure out exactly when it cools down and when it warms up properly. I did this by running up and down a large hill a few times. While climbing said hill the temp would hold around 130*(hard to be exact but its a little below 140*). On the descent, the temp would slowly begin to climb back into normal OT's (140* and above). Essentially I'm now 90% sure it has to do with engine RPM because I ascended and descended the hill at the same speed (roughly 45mph give or take for the error of speedo etc)

Thanks for your help, Oliver
 
#15 ·
The temp sensor is at the rear of the head. It takes awhile for the gauge to react to whatever the t-stat is doing. Increased RPM only make the coolant flow faster, so the gauge lag will be shorter. You are wasting your time trying to troubleshoot using the gauge only.
 
#16 ·
ALWAYS check a new tstat in a pan of boiling water with a thermometer or IR gun. It's fast, free and easy and it removes all doubt from that part of the troubleshooting equation (i even put the old one in alongside for comparison). I have seen to many new ones that are bad. Including Cummins.
 
#17 · (Edited)
@ GAmes, (notice the name spelled correct). So IR gun it is. I don't currently own one so I began searching for one and came to find out there are many different capabilities etc. Anyone I should get specifically?
@Ed Font, thats a good idea. I'd heard that a long time ago from an old hot rod builder but I completely forgot. The good news is that this Tstat doesnt get stuck closed anymore like the old one. It opens at 190* everytime.

Thanks,
 
#18 ·
@ So IR gun it is. I don't currently own one so I began searching for one and came to find out there are many different capabilities etc. Anyone I should get specifically?

Thanks,
I got one at Harbor freight ~$20 Seems accurate at the mid range where most engines operate. I wouldn't trust it for checking EGTs. I don't think you could find anyone to sit on the fender and hold it with your foot to the mat anyway:hehe:
 
#19 ·
Thanks Ed Font, I'll pick one up this week!

Thanks for the help guys. Just trying to learn as much as I can
 
#20 ·
Here's a update: I set the idle at 1000rpm and used the heat gun to measure block temp as well as the top radiator hose and bottom hose. What I found was that while the engine temp was reading 192.5* as read by the heat gun and dash. The top hose read 80* with the tstat housing reading 110*. The lower hose read 130* give or take 1-2* for IR gun error.

GAmes I will try and get the temps after the Tstat opens when I have someone to can push the skinny pedal for me. (I had to use a weight this time)
 
#21 ·
To end this thread with the solution to the problem.

Esentially what I did was begin to systematically rule out potential issues. Starting with the temp sensor and working through another thermostat as well as looking at the fan clutch. The fan clutch was not froze but it did engage the fan a little more then what i considered normal so I replaced it with a Mopar fan clutch which helped a little but not a whole lot. After speaking with my shop they recommended throwing cardboard over 70% of the radiator, which I did and has fixed the problem completely.
 
#22 ·
Thanks for updating this. A search on here should have produced your end result much sooner. I run corrugated plastic in front of my radiator in the cool months.
 
#23 ·
Yeah I agree. I did a search and it came up, the only other cummins owners i know have 24v or commonrails and they dont run cardboard so I thought I shouldnt need to either. Welllll I was wrong haha, as my mechanic politely advised to do so.
 
#24 ·
......they dont run cardboard so I thought I shouldnt need to either. Welllll I was wrong haha, as my mechanic politely advised to do so.
Actually you don't if everything is up to snuff. You have heat now, but you haven't fixed the problem. I've never felt the need to block my radiator, and I only select recirculate to keep the cab warm when the temps are well below 0* F.
 
#25 ·
I actually use some in my 24v when it is really really cold to aid in warm up but I remove it when I plan to tow. I think I do have some problems with the t stat on my 12v as it never gets to 180-190 unless I'm working it hard but haven't been able to tear into it yet.
 
#26 ·
natemoses13, I thought I had tstat issues as well but after the changes Ive made, I've come to the conclusion that they were designed that way.
 
#27 ·
I actually had some time today, so I replaced the t stat again and it is now holding heat quite well. It'll go all the way to 190 then dip to 150 then back to 190 and after a few cycles will level out at 180-190. It's great to have again.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top