Overheating on long pulls?

[dcamilleri]

Took a trip up into the Big Horn Mtns today to do some fishing and test the new fan. Can not budge the tempature needle from thermostat temp! Noise on the other hand is tolerable up to about 65 mph, but kind of loud at 75. HP has probably dropped a little but when you have soooooo much who cares. I checked fuel mileage and got 17. 4 for the trip and that included about 7 miles of rough road in granny. Stay tuned for a long trailer pull around the end of the month. Oo. Oo.

 

[I-6DZL]

Myself and my brother being Auto Technicians, we were doing an engine swap in a 87 k30. We pulled the big block 454 out of it in favor of a 427 that came out of an old school bus. The reason for bringing this up is that the 427 has 2 thermostats in it. Both thermostats are right side by side with both being in their respective holes in the intake and the housing has 2 buldges that flow into 1 huge thermostat housing port.



I wonder if someone could machine a housing that would hold 2 thermostats and still bolt up the same as stock.

I think this would work better because with only 1 thermostat it can't flow enough coolant to keep it properly exchanging heat in the radiator.

I would love to offer pictures, but the engine is sold for a built 454, sorry.

let me know what you guys think... ..... Good or Bad



Curtis

 

[KOdegaard]

dcamilleri,

I have a friend in Hyattville. I have plans to be moving

up that way in a couple of yrs. I know what you mean

about the fishing. The Big Horns are great!

Kirk

 

[dcamilleri]

SHHHHHHHHH... ... the fishing is our little secret. The mountain passes around here are also very demanding. Look me up when you head this way. Dave

 

[SRehberg]

Another thought contributing to the load on the engine, with the temps in the 90's, was the air conditioner on dumping heat on the radiator as well as HP draw for the compressor? Just a thought that could possibly add to a already bad situation.

 

[Berrigan]

Curtis,

Is your feeling that more gpm would help reduce temps and that perhaps our stats dont flow enough?



If memory serves there are a couple threaded plugs on the stat housing. Was woundering if a guy could make up an in cab control to send more water to the rad through those plugs only during heavy pulls. Bill

 

[rweis]

If you send more water does it add to the cooling capacity?



I put a 180* in place of a 190*. Does not add more capacity just sooner.



The 180* cooled things down significantly. I will do a long 5er pull in two weeks to the smokeys. All be it they are not the rockies, but a reasonably good test of the cooling system.



If you tried to ADD to the cooling capacity, what are some possibilities?



RustyJC had a good reply earlier, the cooling system was built to fit the stock system plus some margin. We bomb the hp, bomb the air intake, bomb the exhaust, bomb the transmissions, but not bomb the cooling system.



Maybe we need to generate less heat or look at bombing the cooling system.



Bob Weis

 

[justinp20012500]

Re: Outside the box...

Originally posted by Blue Thunder

Usually the obvious thing we think of when our truck is overheating is the cooling system. However, if you go back and look at the signatures, you'll find a common thread. Those with autos are the one's overheating. The reason is because of the auto not locking up in second gear, causing heat to build in the transmission. Once the trans temp rises above the engine coolant temp (usually about 210*) the stacked coolers at the front of our trucks work against us. Since the trans cooler is in front of the intercooler in front of the radiator, the hot air from the trans. heats the intake air which makes the EGT's rise, which make the engine run hotter, which is trying to be cooled by the hot air coming from the hot trans cooler. Does that make sense???



That being said, the first thing we with autos need to do is make sure we are getting lock-up in 2nd. As long as the valve body is set up for it, all you need is a lock-up device. most trans builders have one available for about $300, or you could use some sort of mystery switch.



My new trans (with 2nd lock-up) is going in next week. I'll know then if my findings prove true.



Granted, our cooling system is likely inadequate for the power levels we are running. So, it would be good to check all the aforementioned devices (fan clutch, t-stat, coolant etc. ).



I am no expert, but you may find this info helpful.

There is also that stupid heat exchanger on the passenger side of the motor. My motor runs at a constant 185-195. My transmission in the summer runs 140- 150. With the coolant surrounding the coils in the heat exchanger you would think the coolant is warming the transmission. And vice versa when the transmission temps are hotter then the coolant. I might be removing mine if I can't get this BHT3B to fit. If need be I will also see if I have to add another transmission cooler. I will have to see how it goes.

 

[Hohn]

I've had really food luck with Redline Water Wetter, though it appears that it slimes up the cooling system. It must not have negative effects, though, since a) the engine runs 20° cooler when pushed 2) the cooling system has NO CORROSION, and 3) I've had no cooling system failures in 180,000 miles of use on 3 different vehicles.



I can only guess that the water wetter slime acts as a water pump lube, It only appears on top of the coolant-- it floats up. It coats the inside of the overflow bottle and makes it look nasty.



But it seems to work well. If it doesn't, believe me, all of TDR will know!

 

[I-6DZL]

Berrigan



Yes that's exactly what i was saying. I do not think our cooling system can flow enough water through the thermostat in order to properly cool the anti-freeze. Think about this for a minute, a thermostat is about 1 to 1. 5 inches in diameter at the thermostat part. If you put 2 thermostats in there that's roughly 3 inches for coolant to flow. The only problem with 1 thermostat is the obstructions in the thermostat that is causing turbulence within the flow of coolant. Just thinking outloud here, with a little food for thought.



don't hold questions back, let me know what ya think.



curtis

 

[RustyJC]

Ummm..... don't you think the Cummins guys sized the thermostat and water pump to get the flow rate they want through the engine and radiator? Engine designers typically design for a specific delta T between inlet and outlet at full load conditions plus some margin (e. g. , our DEMA-rated engines are rated to run 110% of nameplate horsepower for 2 hours out of every 24 hour day. ) That design flow rate, specific heat of the coolant and delta T are then used to size the water pump and radiator. More flow isn't always better (ref. the old wives' tale of just removing the thermostat. )



Rusty

 

[Berrigan]

Rusty, point understood but there still could be room for improvement.



Curtis, As soon as I get a chance Ill look at the configuration of the housing.



Im thinking that there are alot of bombed trucks pulling heavy that need more cooling capacity.



We work to increase engine power. We work to lower egts. We maybe need to work to lower coolant temp. Bill

 

[RustyJC]

Yep, but unless you improve the specific heat of the coolant (it's tough to beat pure water!), the heat rejection capacity of the stock radiator is going to be the limiting factor. Of course, you could put less heat in the radiator (with an automatic, use a large auxiliary transmission cooler upstream of the radiator tank cooler, thus making more radiator capacity available to cool the engine), or change the heat rejection capacity (move more and/or cooler air through the radiator), but playing with the coolant side probably isn't the "silver bullet" solution. You can't transfer more heat than you can shed. Think of it in terms of a refrigerated A/C system. How much good does it do you to double the size of the evaporator coil if you do nothing with the condenser side?



From the engine's standpoint, having the radiator at the back of the heat exchanger stack isn't the optimum placement, but the sales types would apparently rather have you be cool (A/C condenser first) and let the engine struggle for what heat rejection it can get (radiator last) due to extremely high approach temperatures on the air side.



Think about our worst case scenario - that 450 BHP truck pulling a 16K 5th wheel up an 8% grade on a 110 degF day. The A/C is blasting away (dumping heat into the air flowing through the condenser). The turbo boost is, what, 40 or 45 PSIG, so the intercooler is trying to dump far more than its design heat load into the cooling air that's preheated by the A/C condenser. So, when the air finally reaches the radiator, it's probably way above design spec due to the excessive heat from the intercooler. On the engine side, we're trying to dump 450 BHP worth of heat into, say, a 245 BHP radiator (plus a fudge factor). Frankly, I'm surprised that we don't see more overheating problems than we do!



Rusty

 

[Berrigan]

I guess what Im thinking is to look at all pieces of the system. Maybe more cores if there is room. Maybe higher cfm fans. Maybe a Horton type fan that locks.



But also its not uncommon to have a simple cheap mod that makes a big difference. If the stat does restrict flow at high rpm under load then removing that restriction will help. What we need to do is test for restriction. If we find its there, remove it and look to see if we have lower temps under load.



Im game for this cause my cooling system is in good shape and still makes me downshift to bring temps down when I have the power to pull it in a higher gear. Bill

 

[RustyJC]

Originally posted by Berrigan

But also its not uncommon to have a simple cheap mod that makes a big difference. If the stat does restrict flow at high rpm under load then removing that restriction will help. What we need to do is test for restriction. If we find its there, remove it and look to see if we have lower temps under load.

Yes, the thermostat is a design restriction placed in the system to limit flow in order to (1. ) obtain the design delta T across the engine based on the engine's heat rejection rate, the specific heat of the coolant and the residence time required to transfer the heat and (2. ) to be compatible with the water pump's head/flow curve. If one wants to reduce restriction to increase flow for a BOMBed engine, they really need to know what delta T the design engineers want and what flow and head the water pump is capable of delivering.



Rusty

 

[Berrigan]

Well what ever the original design criteria was no longer applies. If we are making more heat now, we need to increase cooling capacity.



I just find it interesting that Curtis has seen an old 427 with dual stats. To me that says that some engineer saw a restriction in that engine that was improved by more flow. Its gotta make you wounder if that could hold true for the 6bt. And it may not.



Time to experiment------------- Bill

 

[I-6DZL]

Bill and Rusty Great points on both parts, But... ... . You can only know what will work if #1 You're a very intelligent and wealthy Engineer that designs the cooling systems. #2 Try and Fail, If you fail, you try harder. My idea was only intended to be exactly what it is an IDEA. Myself i think 2 thermostats will solve 60 to 70 % of the over heating problems.



Rusty the old myth about taking the thermostat out completely is only in my book applicable to Race cars, where more rpm is important rather than hooking onto 16K worth of load. The more rpm you turn without a thermostat the less the water will cool in the radiator. Berrigans case he wants to run less rpm because he doesn't need 3 k rpm to pull his load, so in turn less rpm will move less water and cool ALOT more in the radiator... ... . IF (and in my eyes that's a big IF) the water can get by the thermostat and cool in the radiator.



FYI on our race car we had to have a pulley specially machined to slow the water down in order to let it sit in the radiator a lilltle longer in order to cool the engine... ... ... 388 small block chevy. Stroker crank, . 060 over sized bore, huge 4 core radiator, and engine driven fan.



Curtis

 

[Sixpack]

Originally posted by gonzo2

You might want to take out the intercooler/rad and separate them for a good cleaning.

I ran into a guy up north last week that was encountering similar symptoms. He said that everything looked clean but between the two was caked up with bugs and dirt. Reported that she worked good after.

DITTO!

 

[dcamilleri]

Hey guys,

You don't have to look all the way back to the old 427 for dual thermostats. G. M. went to a dual thermostat system starting in 1997 on their 6. 5 TD along with a higher flowing water pump. When the above modifications were coupled with a 22 inch duramax fan it helped cool some of the modified 300 hp 6. 5's.

 

[RustyJC]

Originally posted by dcamilleri

G. M. went to a dual thermostat system starting in 1997 on their 6. 5 TD along with a higher flowing water pump.

Precisely my point. Reducing restriction in the thermostat area is going to change the point the current water pump is operating on its head/flow map.

When the above modifications were coupled with a 22 inch duramax fan it helped cool some of the modified 300 hp 6. 5's.

Yep, as I said, you've got to do something with the heat rejection capacity of the radiator.



Rusty