View Full Version : Overheating at idle
I have been blessed that I have not had any issues with my truck since it was rebuilt about 35k miles ago.....Until today.
Got home and left it running while I ran in the house to get the mailbox key. Got in the truck and the "check gauges" light was on. The temp. was almost to the red. I shut it off, did a visual inspection...found no leaks. But it did start losing coolant through the overflow tube. I turned the truck back on, fan was spinning fine, still no visual signs of leaking other than the over flow tube.
I let the truck cool down, all hoses were cool to the touch. Started the truck, took it about 5min at idle to get over 210. Forgot to mention I DID fill it up with coolant again. I left the cap off, it did not start overflowing until i turned the truck off.
I have the HO water pump, dual thermostat system...I can't imagine that both thermostats froze...my hunch is the water pump...does that sound right or am I missing something. Any help here would be greatly appreciated.
Thanks in advance,
Bbudus
schamp6497
02-05-2010, 06:03
With any luck maybe your heads and head gaskets are still good. Three things I would do now would be,
1. replace thermostats- cheap
2. pull radiator and have it checked, not just flow check, pull side tank and rod it out if need be. good piece of mind knowing its good
3. just because the fan is turning doesn't mean its good. If its old replace with a known good one. cheap
A good head job with new heads cost about 4,000.00. Do it yourself for about 1,500.00 to 2,000.00.
Good luck.
Radiator was cored when new engine was installed, also had new tranny cooler installed at that time. It also has a new fan clutch and a duramax fan. I was pointing to the water pump, because even if the head was bad the engine heats up so fast.
I had to rebuild the engine and replace both heads because it was blowing coolant out the overflow, but the truck never got uncomfortably hot. Not like this, I mean it was damn near red lined after idling for about 5-10 minutes. It ran fine all the way home which is a 30 mile commute. Also, the tranny temps never went higher than 160. If the radiator was near 250 would that not affect the tranny temp in some way?
After letting it cool down, driving the truck made no difference in temp, just got hot, hot, hot.
I am pulling the thermostats today and going to run it without them at idle to see what happens. I will let you know what i find.
Bbudus
Well crap...took the thermostats out, they were both working fine....left them out and reconnected everything. Started the truck, let it idle for about a minute, no pressure in the radiator hoses, took a mirror to the exhaust, fogged it up like two high school kids on prom night. Could smell water in the exhaust.
So, now i am hoping it was just a gasket, if I didn't love the truck so much I would just shoot the SOB and be done with it. But alas, i cannot. If the heads are bad, anybody know were to get some of the newer heads?
Thanks,
Bbudus
Slow down!
If it doesn't over heat on the road but does in the driveway, the fan clutch is the most likely culprit.
Water vapor is a normal byproduct of combustion.
If you really suspect head/head gasket problems, remove the coolant crossover and fan belt and run it. Bubbles will appear in the water outlet of the head with the problem.
Thanks John, I revert to my old way of thinking with this thing when I see/feel/hear anything out of the ordinary. Which is the damn thing is blowing up.
I left the thermos out, and took it for a spin. I could not get it to warm up, which i believe to be a good thing. Tranny temp got to about 130 after 10 miles of 70mph. Pulled in the garage, no smoke from the exhaust at all. Smelled...well dieselly:) So, I will now put them back in, and test drive it again.
The fan clutch should spin pretty free correct, mine is a bit tight, as in it spins but there is quite a bit of resistance. You are giving me hope.
Thanks,
Bbudus
DmaxMaverick
02-05-2010, 12:48
The fan clutch is [mostly] controlled by the thermostat(s). Stats open, hot coolant flows through radiator, heated air exits radiator and contacts fan clutch, clutch engages. If it overheated at idle, and the clutch didn't engage, then either the clutch or stat(s) is bad. The fan should roar (with any throttle input) when it gets that hot. If not, it isn't seeing "hot" air. Go to the source of the problem.
If the engine overheats, for any reason, it will puke coolant. That's a given. That's how the system works. Under normal circumstances, the system can be up to 15 PSI (or whatever your cap is rated) before dumping coolant. If it didn't, something else would give (hose, radiator, etc.). If it didn't overheat or overpressure with the stat(s) out with a good test drive and a repeat of the idle situation, then it isn't likely a combustion leak. Thermostats, of any brand/rating leave a lot to be desired when it comes to consistent quality. Over the years, I'd say at least one in four are bad out of the box, of any brand. Also, they don't work very well if installed backwards (most often causes overheat and puked coolant).
Ok...new development...apparently, it is not just at idle. Allow me to recap:
1.drove home, normal temp., let idle for about 5-10 min. almost pegged temp gauge.
2. inspected, no fluid leaking anywhere until vehicle was turned off, then blowing out overflow
3. took out thermos, tested, they seemed fine
4. drove truck, without thermostats, could not get vehicle to operating temp after 10 miles
5. reinstalled thermos, copper to the engine, so they are in correctly
6. drove truck, could not go 2 miles and almost pegged needle. pulled over waited about 5 min, truck cooled to about 210, drove home, lost more coolant through overflow
7. allowed to get cold, idled truck in garage, same result if allowed would have tried to peg temp gauge
now the upper hose is hot so it seems coolant is circulating. seems to be some kind of restricted flow or water pump not pumping correctly?
called heath, they suggested i tank the dual system and replace with old single and new thermo. I still think this must be some kind of water pump issue but would like to get more feedback before i tear the front of the truck apart.
thanks,
Bbudus
john8662
02-05-2010, 15:54
Sounds like a waterpump, or hose leading up to the waterpump. They can collapse (the hose) and cause issues. The problem with suspecting the waterpump is that it's so simple and not a common failure point. The only things that I can see that could go wrong with the waterpump is the impeller slipping on the shaft (press fit), or the shaft itself breaking. Would take something in the system to stop the wheel enough to cause damage though.
It's HARD to see if the waterpump is really working on one of these systems that doesn't have the cap on the radiator. On older systems all you had to do was open the cap on a cold engine and see the coolant circulating and tell the waterpump was doing it's thing. Not so with the coolant recovery tank being part of the pressure system.
It's not the dual thermostat housing :rolleyes:.
jerry598
02-06-2010, 10:24
Sounds like a waterpump, or hose leading up to the waterpump. They can collapse (the hose) and cause issues. The problem with suspecting the waterpump is that it's so simple and not a common failure point. The only things that I can see that could go wrong with the waterpump is the impeller slipping on the shaft (press fit), or the shaft itself breaking. Would take something in the system to stop the wheel enough to cause damage though.
It's HARD to see if the waterpump is really working on one of these systems that doesn't have the cap on the radiator. On older systems all you had to do was open the cap on a cold engine and see the coolant circulating and tell the waterpump was doing it's thing. Not so with the coolant recovery tank being part of the pressure system.
It's not the dual thermostat housing :rolleyes:.
X2! Going back to a single tstat will not fix the issue. I'd bet it's a bad waterpump or tstats, or some restriction in the system. If it were a leaking head gasket your upper rad hose should be pressurized and hard to the touch in the first 2 minutes from cold startup.
Thanks for the post everybody. Going to get it warmed up and check the lower hose. If it's good, the water pump is coming out. I will let you know what I find.
Thanks,
Bbudus
DmaxMaverick
02-06-2010, 12:37
Water pumps rarely, ever, fail to pump. When they fail, it is either the seal or bearing (which usually go hand in hand). When you have a temperature issue, the water pump is the LAST suspect. If it isn't leaking or making noise (remove the belt and give it a spin), look EVERYWHERE else first. Sure, the impeller could be spinning on the shaft, or the shaft broken. Your radio knobs are more likely to fall off during a summer breeze.
At idle, during winter temperatures, about the only thing that might cause your issue is some sort of a restriction. The lower hose is probably the right direction to begin with. If it is "soft", replace it. If it has a kink, replace it. If it has any blisters, replace it. If you don't know how old it is, replace it.
Diesel engines, operating normally, generate very little heat at idle. Even with a blown head gasket, they don't get hot until the coolant is gone. It sounds like your coolant overheated, then blew out, not the other way around (such as a head gasket issue).
Back to the thermostats.....The dual stat isn't the problem. Toss that idea out. Changing back to a single, if it fixes the problem, would be no more than coincidental. If you can't duplicate the issue with the stats removed, that's probably the source of your problem. They are either bad, or installed incorrectly. Double check their direction of install. The large spring must face toward the block, and not the radiator hose. If you don't have an application-specific stat installed, that could be your problem. The correct stat for your engine should have bypass holes in the disc. These are necessary to circulate a little bit of coolant during low volume periods (like idling) to expose the block-coolant temp to the stat. The stats are remote, as opposed to older styles (actually mounted in the manifold), and can be isolated from actual coolant temps without some flow. The result is a run-away temp condition. Changing the heater hose routing can also cause this condition, as some designs rely on heater core flow to expose coolant heat to the stats.
In any case, you will be draining the system for one reason or another. Replace the coolant with fresh water and leave out the stats. Leave the upper hose off at the radiator. Start the engine. If water flows, the pump is pumping.
a5150nut
02-06-2010, 18:10
Has all the air been bled out thruogh the brass bleed nut?
Slow down!
If it doesn't over heat on the road but does in the driveway, the fan clutch is the most likely culprit.
The fan clutch serves 2 purposes. The well known one is to "lock up" when the coolant temps get high, bu the less well known one is to drive the fan at reduced speed when the coolant is not too hot. On the highway you have higher engine speeds, higher fan speeds, and forced airflow due to the forward motion of the truck. In the driveway you have nothing but the fan. If it isn't being driven you'll overheat and the clutch will not engage (even if it could) because the hot air from the radiator is not reaching the clutch thermostat.
Tomorrow is the day. Was supposed to be today but life intervened. I will try Dmax's theory first, as it is logical. My thinking was that the water pump was floundering just enough to move coolant with out the tstats, but with them in they were to much of a restriction.
Again, all the hoses, radiator, tstats, water pump, so on and so forth are all fairly new (engine only has 35k on it). But *#@& happens right, so I will check all hoses and then move forward with the test. I cannot tell you how relieved I am that everything is pointing away from a head gasket issue.
John is there any way to test to see if a fan clutch has gone bad? I have a few ideas, but I can't be the first with this issue, so I will defer to experience.
Thanks,
Bbudus
schamp6497
02-07-2010, 07:50
I would still check the radiator. I asked a well known group (on this site anyway) to have my radiator reworked and thought they had. Didn't happen. For piece of mind and an about 80 bucks have it checked. I am betting its fan and somewhat restricted radiator. When running down the road without a load it getting enough air to cool. Not so when idling. Kennedy Diesel used to sell a better fan setup. May still. Good luck.
John is there any way to test to see if a fan clutch has gone bad?
With the engine warmed up, shut it down and spin the fan by hand. If it spins easily and coasts for more than a turn or so, the clutch is probably shot. Compare with a known good example if you can.
Also, if your temp is getting above 230 or so and you are not hearing the fan clutch engage, something's amiss...
On a cold start, the clutch often will act as if it is engaged due to the fluid puddling in the bottom of the housing. If you get the RPM's up to 1800 or so you'll notice the roar of the fan. This usually subsides after 1/2 mile or so. Again, if you don't hear it, something is probably amiss.
I agree with the above advice. The consdensation you got from the exhaust after a few minutes' running is normal, and not evidence of a coolant leak.
Dug in today, pre-Subparbowl. After getting the shroud off, checked the lower hose. Right by the water pump the hose was very....soft. Didn't feel as though there was any spring to it. Took the fan assembly, and lower shroud out. Drained the coolant and removed the hose. That same "soft" spot looked flat. Had to order the hose, will be here tomorrow morning.
The plan is to replace it, fill full of water and let it get to operating temp. If that does not work will be ordering two new tstats. Probably call Heath, there closest, and I'm a tight arse and don't wanna spend the extra on shipping:)
After that will check water pump. I realize the truck will more than likely run a bit warm without the fan, but I should not see the spike in temps.
Everything looked fine though, nothing was jumping out other than the lower hose, so I am hopeful.
Thanks,
Bbudus
midniteplowboyy
02-08-2010, 08:07
Sounds like a small headgasket leak letting letting in enough compression to airlock the stats.
I reread your first post. Are you saying it goes from cold start to 210 in 5 minutes?
I would not run it for more than a few minutes without the fan.
It did, replaced the lower hose, let it idle without the fan for about 10min or so, got to operating temp, then climbed to about 210 and held steady. So that is improvement. The upper hose is getting warm, then hot, but i do not feel coolant moving through it. Then, only the lower half of the radiator was warm, and now I have no heater.
I sat there and bleed the tsat housing, left the overflow cap off, and when it got really hot(210) it finally start coming out the overflow, at no point did I need to add coolant. Yet, no heat...my brain hurts. It has to be the tstats or water pump, its like i have no flow whatsoever. Once it cools down again I am removing the upper hose from the radiator and run it until it gets hot, that should tell me more.
As always your feedback is invaluable.
Thanks,
Bbudus
If only half of the radiator is warm it must have air in it. The heater not working also suggests air in the system. The t-stat housing is the highest point other than the overflow tank. If you pour water in the tank and it comes out the bleeder, the radiator must be full. The only catch is it takes some time for all the air in the block to bleed out through the closed thermostats, so it can air lock again.
Keep bleeding it...
not to mention all of the air that can get stuck in the rear heater core and hoses.....takes quite a while to get it all out.
Did you run it with the fan removed but the belt still on, or with the fan on and the belt off? I just want to point out the obvious. If the belt was off while you ran the engine there would be no flow due to the pump not turning. Just checking.;)
Ha ha, yes the belt was on:) Will get back on it in the morning. Hopefully by noon there should be a resolution to this issue....my sanity is at stake here.
Thanks,
Bbudus
Ok, we are getting there! Almost have heat. Still burping the air out. Good news is the temps are back to normal. No fan, or clutch and it will idle at about 190 degrees, highest it climbs is about 210, but that takes awhile. But I found another issue. Hole in the radiator right next to the lower hose, not big but enough to get it fixed. This thing has been rodded and a new tranny cooler installed. I am just going to scrap it and get a new one. Anybody have any suggestions? If I am going to do it I might as well go all out. I don't want to do it again for a long time.
Thanks,
Bbudus
Update: New radiator is in, new thermostats are in, lower hose connected. Filled with 60/40 mix, burped out air. Truck warmed up fine. Took it for a spin, heater is hot, truck drove normal. Then got a "check engine". Code 48, air intake temp is to cold, have no idea what that means. But did get some coolant on the sensor, so maybe it is just shorting. Sprayed some wd-40 on it, no help. But the frustrating part is, was topping off tranny fluid, truck at idle, went over 210 again, then when I turned the truck off, belched out a bunch of coolant.
So, now I am going to replace the radiator cap, and look at a new fan clutch. When I reinstalled it, i could hear it, but it seems that once it gets warm it kinda craps out. I know the water pump and new thermostats are working because I can see on the temp gauge when they open.
Getting to the end of my rope here. Any thoughts on the code 48 or the heating issue is much appreciated.
Frustrated,
Bbudus
Yukon6.2
02-18-2010, 09:02
Hi
Have you confirmed that the motor isn't pressure the coolant system?
It's where i would look next.The motor in my tow truck was doing very similer stuff.It would overheat/get hot every time after startup if it sat for a while/overnight.I would get the air bled out then it would be fine till it sat again.
I pulled the thermostate crossover and the belt,then started it.it started bubbling on the drivers side right away.
Switched motors,problem solved.
The problem was after sitting.once the air was bled out it was fine,could even tow with it and it wouldn't overheat.
I havn't dug into the old motor to see what happened,it's very low on the project list.
Thomas
DTC 48 probably means the air temp sensor didn't get reconnected, or is damaged. Open circuit == too cold.
Pull the coolant crossover off and run the engine without the fan belt installed. Look for bubbles in the coolant outlets on the two heads. The one that bubbles has a bad head gasket...
Ugh...this truck is going to be the death of me. Now it wont start. I will start a new post on the DTC 48, as it has nothing to do with overheating. Have to get it started before I can continue down that path.
For mercy's sake,
Bbudus
Bubbles!!!....Bad head gasket on the drivers side. Almost have it out, so we shall see. The water pump crapped out, so I am thinking it got to hot, to fast and that is what fried the gasket. Hoping no other damage. This truck has one more year of ownership left and good bye and good riddance. Time for me to graduate up to the 21st century. Duramax...I like the way that sounds. Just rolls of the tongue...Duuurrraaamaaax!!
Thanks for all the help, will report back once this project is done to left folks know the end result.
Bbudus
Yukon6.2
02-23-2010, 08:57
Sorry to hear about the bubbles.Don't write off the older truck so fast.
Duramax also means lots of bucks for repairs,3 to 4 k for injectors,they can have headgasket/injector tube leaks,all repairs you can do yourself,but not as easy or as cheap as the 6.5.Take it to a dealer and watch the $$$$ roll out of your pocket as easly as duuurraamaax rolles of your tounge:rolleyes:
Good luck
Thomas
Ha, ha, Yukon:) I get to keep him(names Jim, Jim C.) for a couple more years yet it seems. The gasket failed on the #7 cylinder, compression was seeping through the gasket into the water jacket. None of the head bolts had sealant on them, and two of the head bolts were not torqued down all the way( checked every one). All this from a "reputable" local shop here in Billings.
Ah well, no point cryin' over spilled milk, finish cleaning it up tonight and reinstall tomorrow. On a side note, pulled the water pump. Works fine, so it was air locking. Tricky. Anyways, by tomorrow should be up and running again, although I am worried about the other head now. I report back then, hopefully with good results:)
Bbudus
john8662
02-23-2010, 20:15
Carefully examine the gasket. Cylinder #7 would be a common one, end coolant port failure. Ensure you get the re-inforced gasket, see if the one used was old stock.
Head bolts, ensure you're not re-using these. These are TTY, use once throw away. The sealant is pre-applied on the bolts as a dry sealant. This sealant is awesome to say the least. So if you had bolts with none of it, then it's possible the previous mechanic reused the bolts. If that's the case, you're gonna be doing the other side sooner or later.
Just thought I'd offer this advice while it's still apart.
J
Are you replacing the head bolts? That could have been the problem before...
Might be worthwhile to replace them on both heads, for that matter.
Yep, pops told me a long time ago, do it right the first time, wish the guy rebuilding my engine had somebody to tell him the same thing. The big debate in my head at this point is doing the other side now...or wait, I am due for a turbo replacement, and I really need this thing running....may try and hold out till this spring and replace the passenger side head gasket and bolts when I put on the new turbo. Hell, after you get the turbo off you are half way there anyways. I will make the call tomorrow when I pick up my parts, usually that little voice in my head wins, and it is for fixing it now. Along with glow plugs....on that subject, would you do the bosch or the delco 60's? I am leaning towards the bosch.
Thanks for letting me rant a bit,
Bbudus
This will not benefit anyone, but I never had to change a single glow plug on either my '93 or my '95. On the (ford) it was about every oil change...
YMMV...
Finally done with the upper engine rebuild. I am quite suprised it ran at all. Nothing was torqued down, the intake all but was hand tight. Anyways, it is put together correctly now. No more heating issues. Did find that the waste gate on the new turbo was locked shut. Had to take a hammer just to get it to move. Luckly I had another laying around. Thanks for all the help, still am having a DTC 48 issue, but I will talk about that on the other thread.
Thanks,
Bbudus
Powered by vBulletin® Version 4.2.5 Copyright © 2024 vBulletin Solutions Inc. All rights reserved.