View Full Version : 6.5 Runs a lil' too hot. Tips to bring it down?
JSteward
09-14-2006, 19:40
Runs about 220 with the A/C running with no load. I'm gonna have to pull a 7500lb RV in about a week. As I understand it, my early production model '96 has a single thermostat and a weak water pump...
I've read that you can install a double thermostat system. If so, would I need to purchase a different thermostat housing? What type thermostats would I need to replace with?
As far as the water pump, can I order a factor replacement for the '97 model or is there a better water pump that could help it run cooler?
I've ordered an oil temp guage, boost guage, and egt guage which I'm sure will help me to further diagnose the heat problem.
Any other tips you could give to help bring the heat down (without having to spend too much).
Thanks
If you haven't already done so. Check in between the radiator and condenser. That sounds high even for having the single thermostat, especially with no load. I pulled my trans. and oil cooler away from the condenser and couldn't believe how much stuff was right behind them. I replaced my radiator because of a very small trans. cooler leak, but when I removed the old one there was tons of stuff in it and the condenser. I'd check that first.
And then I would also just pull the Rad. and clean it up good inside and out.
The one thing I've done has to do with laying Rad. flat on the floor and fill with a mix of CLR and water. Once you know the inter's are clean than only use destiled water. Most Rad. will last a long time with fresh antifreeze changes.
JSteward
09-15-2006, 15:51
If you haven't already done so. Check in between the radiator and condenser. That sounds high even for having the single thermostat, especially with no load. I pulled my trans. and oil cooler away from the condenser and couldn't believe how much stuff was right behind them. I replaced my radiator because of a very small trans. cooler leak, but when I removed the old one there was tons of stuff in it and the condenser. I'd check that first.
The engine compartment has been steam cleaned. Radiator is completely spotless...
I almost forgot, the "low coolant" light comes on when it gets hot. The coolant level is full and it doesn't seem to be using any. Actually, it only came on twice since I've had it and I was running up a long incline (hill) for quite a distance and I was getting a little hot. I also had the a/c on. I don't know if this is related to the issue or not, but the light came on and stayed for about thirty seconds or less.
I'm thinking maybe the coolant wasn't flowing enough. ...perhaps the dual thermostats could remedy this. Anyone have more info on how to upgrade to the dual system and better water pump?
Thanks.
DennisG01
09-15-2006, 16:00
Do as stated above - look between radiator and condenser. I highly doubt that the person you bought the truck from cleaned there. It's pretty easy to do, though. Just unscrew and remove the black plastic fan shroud. It may not solve your problem, but it's good thing to check before you go any further.
tommac95
09-15-2006, 21:08
The dual thermo + big water pump ("'97upgrades") are a big improvement. [later heads had larger cooling passages too].
If the radiator (and the space between it and the condensor) are clean, then probably your old thermo is shot ... or maybe the water pump isn't pumping much. The stock cooling system should cool OK when running light (not towing). Of course if the timing chain is real worn, and a couple cyls are weak, maybe not.
Check into this http://www.kennedydiesel.com/detail.cfm?ID=32
http://www.kennedydiesel.com/detail.cfm?ID=33 This help with those who tow.
Not hard to do and JK can walk you through.
At this time while I was doing my cooling up grade, I also went with the DSG gear drive http://www.kennedydiesel.com/detail.cfm?ID=46 that replaced the chain.
Ditto on cleaning the radiator, & AC heat exchanger,
Especially if run on dirt roads, Fine sand/grit gets packs
in the fins, Makkes a big differance,
Also clean the Oil cooler and trans cooler....
180 deg thermostats also help, the Correct ' high flow'
ones...
JSteward
09-16-2006, 09:24
The dual thermo + big water pump ("'97upgrades") are a big improvement. [later heads had larger cooling passages too].
Which brings me back to my original question... What type of thermostat would I need to order? In other words, what would I need to tell someone that I needed? Two thermostats for a '97 (my truck is a '96)? Will they plug right into a one thermostat system? Do I need to buy some type of adapter or a two therm housing?
Same for the waterpump. I realized that there was an upgrade available. Should I just ask the parts house for a '97 water pump, or is there a better water pump available via internet? I want the best for my model truck. What do I ask for?
Thanks all who have responded.
JSteward
09-16-2006, 09:29
Check into this http://www.kennedydiesel.com/detail.cfm?ID=32
http://www.kennedydiesel.com/detail.cfm?ID=33 This help with those who tow.
Not hard to do and JK can walk you through.
At this time while I was doing my cooling up grade, I also went with the DSG gear drive http://www.kennedydiesel.com/detail.cfm?ID=46 that replaced the chain.
THANKS! This is what I was looking for.
There were some 96 models with OEM,97 HO cooling,
Look for a 'y' at the thermostat housing, thats the HO
It is very obvious , follow the top hose back to the block.
I think someone mentioned this before but clean between the radiator and condenser first. If you have not looked in there yet and want some idea of what may be there take a look at my site for some history.
http://mysite.verizon.net/vze54tx9/
You will most likely find leaves in the lower left corner because of the way the radiator is enclosed that is the collection point. My radiator was about 20% covered when I bought the truck.
One thing thats really good especially if you live in an area that has crappy water.
Flush the system completely and get all the coolant out of the block and radiator as well as the heater.
Refill with ELC (Extended life coolant) This stuff is premixed and you DONT add any water or other coolant additives.
Dont ever mix regular antifreeze either.
This stuff is very good for the system and prevents corosion and other sinister things.
I use it evclusively in my big rig.
Its a redish color and is available from several companies. Cat sells it and so does Shell.
I am sure many others do too.
All the sound advice I see here will give your little diesel rat a fighting chance in the heat.
I am running a 180 stat in my 94 and it seems to be doing fine in the hot weather.
Great stuff
Robyn
Mark Rinker
09-17-2006, 09:24
I own two 1994 K3500s. One has a newer '98 engine with the cooling mods, hiflow water pump and Kennedy fan clutch.
I have been running the other stocker with NO thermostat up here in Minnesota for almost two years. In the winter, it takes a little longer to get up to temp, but has no issues making plenty of heat and running in the 160-180 range, even on cold winter days.
You might try this little trick and see what results you get. IMO, the biggest restriction to flow on the old the single thermostat system is the thermostat itself, and you can't hurt the engine by trying this. If it runs too cool, you have at least eliminated other sources of restriction. If it still runs hot, you have issues elsewhere.
Running with out Tstats in cold http://www.cabelas.com/cabelas/en/templates/pod/horizontal-pod.jsp?id=0005914&navCount=1&parentId=cat20133&masterpathid=&navAction=push&cmCat=MainCatcat21412-cat20133&parentType=index&indexId=cat20133&rid=temps
Mark Rinker
09-18-2006, 04:53
Yup. That should work, and also keep the coolant flowing at max levels. Not ideal, but an economical work-around for an older vehicle.
In my case, the incoming air is restricted by a Western snowplow that spends most of its winter 'hanging around' in front of the grill ... :)
JSteward
09-18-2006, 15:42
[QUOTE=Mark Rinker]
I have been running the other stocker with NO thermostat up here in Minnesota for almost two years. In the winter, it takes a little longer to get up to temp, but has no issues making plenty of heat and running in the 160-180 range, even on cold winter days.
You might try this little trick and see what results you get. IMO, the biggest restriction to flow on the old the single thermostat system is the thermostat itself, and you can't hurt the engine by trying this. QUOTE]
If I run no thermostat, how often will I have to replace the coolant? Is there any other disadvantages to no thermostat?
...that seems a lot better than paying $360 for a dual thermostat & coolant system upgrade.
In Mark case,this is OBD I controled Comp. With the OBD II there could be issues. Have you looked to see if your indeed a single stat system?
JSteward
09-20-2006, 16:48
In Mark case,this is OBD I controled Comp. With the OBD II there could be issues. Have you looked to see if your indeed a single stat system?
It has one thermostat and was purchased in '95 (originally).
I just got in my guages and I'm trying to install them. I got an oil temp, trans temp, boost, and egt guages. I'm sure they will help to diagnose the heat problem...
It wont make a big difference at highway speed, but I have found that an old fan clutch seldom brings the fan up to speed the way it should. After replacing the clutch, I find a cooler running engine, and colder A/C due to more air being pulled across the condensor. My 6.5 has Bill Heath's clutch, which is supposed to lock up sooner than factory, and move more air. I pull loads only in flat FLorida, and see temp rises only when first accelerating when heavy, and they quickly go back down when the clutch engages. You can hear the fan inside with the windows up- it roars when engaged.
Rick
When mine was running Hot, the fan clutch would not kick in untill the temps were on there way to the red line,
After cleaning the radiator, condensor , oil and trans temp
coolers, and installing 180 degrees theromaststs.
the temps very rarly get up to 210, when it does the Fan kicks in, temps go down imediatly,
I believe the radiator, etc was so clogged that not enough heat was getting to the fan clutch, ala , delayed fan clutch
engage,,,
JSteward
09-21-2006, 15:41
When mine was running Hot, the fan clutch would not kick in untill the temps were on there way to the red line,
After cleaning the radiator, condensor , oil and trans temp
coolers, and installing 180 degrees theromaststs.
the temps very rarly get up to 210, when it does the Fan kicks in, temps go down imediatly,
I believe the radiator, etc was so clogged that not enough heat was getting to the fan clutch, ala , delayed fan clutch
engage,,,
...my radiator is VERY clean. The truck has never been taken off the road and appears to never have been driven at night as there's absolutely not one single sign of bug or stick anywhere in front of nor behind the radiator.
I have a question about that fan clutch. You said that it made your fan move more air and you could hear it roar inside with the windows up... is that with a stock fan? I don't see how a clutch could increase air movement. I don't know a lot about it, but isn't the clutch just supposed to tell it when to engage?
Thanks
DmaxMaverick
09-21-2006, 18:33
...my radiator is VERY clean. The truck has never been taken off the road and appears to never have been driven at night as there's absolutely not one single sign of bug or stick anywhere in front of nor behind the radiator.
I have a question about that fan clutch. You said that it made your fan move more air and you could hear it roar inside with the windows up... is that with a stock fan? I don't see how a clutch could increase air movement. I don't know a lot about it, but isn't the clutch just supposed to tell it when to engage?
Thanks
The fan clutch is a fluid coupling, not unlike a torque converter. Internally, the fluid passes through vanes and passages as the shaft speed is more than the head spead. Light duty (small car) clutches rely only on this fluid friction, and the fan will never get near shaft speed. On a HD, or truck clutch, it also has a bi-metal spring on the front. As that spring heats up, it twists a shaft connected to a valve that increases the fluid friction, causing the head to more closely track the shaft speed. Even with that, the fan will never match shaft speed, but get closer to it as the temp increases.
What causes the clutch to engage/disengage? The thermostat(s), and the A/C condensor to a small degree. The clutch is effected by the temp of the air passing through the radiator. As the stat opens, the coolant temp in the radiator increases, as does the air passing through it, and this air meets the fan clutch. A more aggressive clutch will have a tighter tollerance internally, and/or a more sensitive bi-metal coil. Beware of "High Performance" clutches. Many of these are nothing more than a Heavy Duty OEM clutch, which is exactly what came originally on most 6.5's from the factory. The only "High Performance" clutch I am aware of is only sold by John Kennedy, and is designed and manufactured to his specification. All others are available through normal distributing channels.
JSteward
09-21-2006, 20:08
The fan clutch is a fluid coupling, not unlike a torque converter. Internally, the fluid passes through vanes and passages as the shaft speed is more than the head spead. Light duty (small car) clutches rely only on this fluid friction, and the fan will never get near shaft speed. On a HD, or truck clutch, it also has a bi-metal spring on the front. As that spring heats up, it twists a shaft connected to a valve that increases the fluid friction, causing the head to more closely track the shaft speed. Even with that, the fan will never match shaft speed, but get closer to it as the temp increases.
What causes the clutch to engage/disengage? The thermostat(s), and the A/C condensor to a small degree. The clutch is effected by the temp of the air passing through the radiator. As the stat opens, the coolant temp in the radiator increases, as does the air passing through it, and this air meets the fan clutch. A more aggressive clutch will have a tighter tollerance internally, and/or a more sensitive bi-metal coil. Beware of "High Performance" clutches. Many of these are nothing more than a Heavy Duty OEM clutch, which is exactly what came originally on most 6.5's from the factory. The only "High Performance" clutch I am aware of is only sold by John Kennedy, and is designed and manufactured to his specification. All others are available through normal distributing channels.
DM, you are one stand up guy! I greatly appreciate your answer to this question (and my other posts)... very detailed and thoughtful.
It will be tommorrow afternoon or Saturday morning when I take my 7500LB RV on a 6 hour pull. I've decided to take out the thermostat to head off any heat problems. As soon as I get settled into my next job location (I pipeline), I'll be ordering the '97 cooling upgrades and a 4" straight exhaust system. That should have me running cool. Thanks to everyone who replied to my post!
My condensor got ' grit' from the back roads in Montana and Dakota's, Had to clean each slot with a metal feeler gage,
Yes, I can here it inside, you will also see temps drop
very quickly, On a long hill in PA, the clutch and temps would cycle, But the max temps were at the red line,
the gage as ref, would show about 230 degrees before
clutch kicked in...
after cleaning , and the 180 deg thermoststs
Temps stayed much lower.
I could get the fan clutch engaged on I26 going up to ashville NC, but max temps about 220 degrees
I too once thought my radiator was clean as could be, until I had to remove the oil cooler to change the lines. The fins on the cooler are at about a 45 degree angle to the fins on the condensor. Dirt stalls out at the condensor and can't make the turn. There was zero air flow through the cooler, condensor and radiator under both the oil and the trans coolers.
YMMV
JSteward
10-04-2006, 07:21
First, I'll reiterate that the radiator and entire engine compartment are spotless. There are no bugs or debris nor bent places that would restrict air flow...
I removed the thermostate entirely and the truck STILL runs hot! I'm perplexed... It only seems to run hot whenever it is idling. This made me think that the fan clutch may be going out. I popped the hood and checked the fan and it was turning...
The temp gets up to about 220 (w/ no thermostat) and would probably boil over if let idle over 30 minutes. Is this typical of the inferior early '96 water pumps? How could I check to see if my water pump was working?
Thanks.
moondoggie
10-04-2006, 09:53
Good Day!
"First, I'll reiterate that the radiator and entire engine compartment are spotless. There are no bugs or debris nor bent places that would restrict air flow..." Unless you've unbolted & moved the engine oil cooler & tranny cooler, you will not see what's stuck in your A/C condenser. ;) Your answer doesn't address whether you've done this or not.
When I looked into this on my 95's & my daughter's 89, all looked perfectly clean. When I tipped the coolers out of the way, the A/C condenser behind them was COMPLETELY plugged. The same was true of the radiator when I tipped it from behind the A/C condenser. My brother's a mechanic. His theory is that the 1st device in the airflow slows down the bugs etc., the 2nd is the one they stick to. He sees this with every car he works on (the place he works gets mostly lower-middle-class vehicles, > 100K miles).
"...and would probably boil over if let idle over 30 minutes." Sorry, I've never idled my 95's that long to know. I don't think they would unless it was 80F or warmer outside, but really have no hard data. :(
Please forgive me & JohnC for being redundant, but we're only trying to help. :D You didn't say whether you've done the above or not, just restated that everything's clean. Saying everything's spotless is not the same as saying yes, I did that & all is clean. While our being redundant might frustrate you, please remember that it's also frustrating to do your best to help folks & not get clear answers to the advice offered. You owe no one any explanations; I'd only ask that you accept the help here in the spirit given - we'd like to help you succeed. ;)
Blessings!
moondoggie
10-04-2006, 10:03
Good Day!
"...that seems a lot better than paying $360 for a dual thermostat & coolant system upgrade." If you're only infrequently going to pull heavy, true; at some point the upgrade is beyond doubt worthwhile. The original water pump did something like 80 gpm (corrections please); the upgrade pump does 130 gpm. The combination of this pump & the dual thermostats increases flow through the radiator ~ 9%, but increases flow through the block ~ 75%.
I too haven't upgraded either of my 95's, due to budget constraints. I don't tow often or very heavy, & live with what I've got when I do.
Blessings!
(signature in previous post)
Yeah, not to sound like a broken record, but if you haven't pulled the various coolers apart, you can't be certain they are not blocked. Mine looked spotless on the surface (pun intended) but was completely blocked behind the oil and transmission coolers.
Your symptoms sound like either the fan clutch is shot or the radiator is not flowing air well. They are not typical, even without the cooling system upgrades. Don't spend any money upgrading anything until you figure out what is really the problem.
moondoggie
10-04-2006, 12:26
Good Day!
"I'm gonna have to pull a 7500lb RV in about a week." I just pulled an IH 2500A tractor (industrial version of the 574) with loader & cab on a tandem flatbed trailer, the bed being above the tires & axles. So, the tractor was fairly high in the air, even though this is a very short tractor, even including the cab (which is why he bought it). The tractor is listed at 4800 #, but I'll bet that's without fluids. With all fluids (I don't know if there was any in the tires), loader, & cab, I bet it weighed 7000 # or so, PLUS the trailer (1500#? 2000#?). I pulled it 65 mpg with ease on our VERY flat highways (169 NB from Rogers MN to Mille Lacs). It handled the tiny "hills" in the highway fine, but would have had trouble with any hill with any length at all. Fortunately (or unfortunately, for the sake of collecting data), it was ~ 65F that day, so nice & cool & no A/C needed. I pulled it with our Sub, which has 3.42 gears & no mods other than JK exhaust & -1.94 TDCO.
Soooooo, if a guy can take it easy on the hills and/or doesn't tow real often, your setup ought to handle this RV with no trouble.
Please let us know what you find - it will help all of us. ;)
Blessings!
(signature in previous post)
I assume you looked at my web page to see what we have been talking about when we mention a restricted air flow through the radiator. I am still willing to bet if you put a trap under the truck and backflushed the AC condenser and the radiator you would cover the tarp with bugs. I cleaned a friends system who was sure his radiator was clean and suprised him with the bugs.
Another problem I have seen, not on GM trucks but on a Dodge, is the blades on the water pump desolve so only the back plate remained. Without a cap on the radiator it is hard to just rev the engine and see if you have flow through the radiator but it might be worth removing the pump if it is original and checking.
JSteward
10-06-2006, 06:01
SITUATION RESOLVED. First off, as Moondoogle pointed out, I was too quick to dissmiss the sound advice of those with years of experience in such matters based on my inexperienced limited observations. I pulled the radiator yesterday and there were buggs in the back side. However, the main problem was that there was some oily residue all over it which had caused dust to stick to it. I put some engine degreaser on it and washed out a pool of black liquid. I put the hose to the radiator and washed out all the dexcool. I installed, filled back with water, ran five mintues or so, then drained the water and filled back up with regular green antifreeze.
Truck now runs about 185 instead of the 210.
Thanks for all the help and sorry I didn't give your (plural) advice more weight.
moondoggie
10-06-2006, 18:05
Good Day!
I think I'm safe in saying for all of us, we're just glad you found what was wrong, & many thanks for the update. :D Your update will help many who search these forums in the future, which includes me - I can't seem to remember anything anymore! :(
Blessings!
(signature in previous post)
Hello... when I started working on my truck... I removed grill guard and grill, fan and shroud... and then I proceeded to use high pressure washer to clean out the rad/coolers... I even lifted the front of the truck 3 feet in the air to do the underside... I spent a long time (60 minutes) washing with commerial (2500 psi) washer
and I was so sure that rad would be clean... removed a few more items and washed all over again...
then I pullled the oil cooler away to install the SS lines and I could not beleive the junk behind the cooler against the AC condenser... so all my washing did not make it though the first oil cooler... but when you looked at the rad, front or back... it looked clean... behind the trans cooler was also a mess :eek:
Then I pulled the rad so I could look at it and clean again... it was still very dirty... swing all the coolers away from the front, remove the rad, and then you can clean the AC conditioner in the truck...
plus you get to straighten all those folded fins from the years... if 2500 psi water can't get through a 2 inch wide oil cooler (and my rads/coolers were just dirty with bugs... not oil or coolant soaked)... how could air ever get through there...
just because it looks clean in the places you can SEE... doesn't mean it clean;)
PS>>> that rad is one very EXPENSIVE item ($700.00 at GM) so be very carefull with it!
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