6.2 Operating Temp Question- Didnt want to thread jack

[viggen]

There is the cool down thread but I didnt want to thread jack so Im starting my own. I am looking at buying a Land Rover Discovery with a 5 speed and a 6.2 NA in it. Its a HMMWV motor with low time that was swapped in. It runs great, accelerates smoothly, starts up with 15 seconds of glow (converted to 12v but still runs dual batteries), doesnt smoke at all and is unbelievably smooth. Being a 'hybrid,' there are a few Sunpro aftermarket gauges on it (mechanical oil pressure (40 cold and about 30 at 190) and electric temp). It has a large aluminum radiator, not sure of the dimensions but its pretty large with, Im guessing here, about 3" of thickness, and runs dual electric fans off a switch in the side tank of the radiator. The truck and the motor as a whole are fantastic but here is my question: proper operating temperature is what for this motor?

Ive driven the truck at 65 mph for a few miles and its temp was solid at 190 (ambient temp is in the 90's with a dew point around 70 or higher so it feels like upper 90s almost 100). Around the back roads at between 40 and 50, it runs around 190 also. I hit a few hills, one of which required a downshift from 5th to 4th and temp went up to about 195 and then settled back to 190 as soon as the hill was over. Talking to the owner and asking about the highest its ever peaked, he says 210 to 215 or so but it always settles back down to 190. Operating temp is the only thing that bothers me about the truck. I live in Northern Virginia which is flat but the truck will be in West Virginia quite a bit and well, that is anything but flat. If temp jumped just going up a hill and he has reported temps up to 215, I cant imagine what might happen when it has about 1000 lbs worth of gear and people inside it going through the WVa mountains. What temp is danger temp?

[Burbinator]

190 is about right for both naturally aspirated and turbo motors. 210 should be regarded as the maximum upper limit. Anything over 210 is going to hurt your motor, especially when you're in hill country like West Virginia while towing or carrying a lot of weight.

[viggen]

So, redline is at 240, and 215 is 3/4 gauge and thats not that good. What would an exhaust do to the operating temps? Right now it has the stock 3.9 liter V8 y pipe to a single probably 2.5" single exhaust.

[Robyn]

Adding a dual 2-1/2 exhaust will not hurt it a bit.

The biggy for keeping these engines cool is the size of the radiator and having an engine driven fan. The electrics just can't pull enough air through to really cool things.

If you can add even a small engine driven fan along with the electrics, you would gain a lot.

I am not familiar with that particular vehicle as far as the room it has under the hood so I can't say for sure about adding a fan.

Keeping the temps down below 220F is a real plus for engine life.

I would install a 180F stat in the thing too, this gets the water moving through the radiator a little earlier and gives things a chance to cool down some.

With a 180F stat, the thing starts to open at 180F and will be fully open at around 190F
With the 190-195F stats they start to open at these numbers and are not fully open until around 200-205F


Hope this helps


Missy

[convert2diesel]

For the most part, I agree with Robyn's suggestions but the one area I have proven is not an issue with the NA 6.2s is the use of a mechanical fan. Due to space limitations in the Buick, I was forced to delete the mechanical fan and in its place, I used two electric fans from the police varient of the 94-96 Chev Caprice and had a four core rad built for the car. When towing I use the 180 stat and have the fans kicking on at 195.

The only time the fans turn on is in summer traffic, when I use the AC and on long uphll pulls with the camper out back. The big test was coming out of North Carolina into Virginia on I77, outside temps at about 80 degrees and a 10 minute consistant uphill climb. Had the 3,000 lb camper out back, third gear, 65 mph and the temps never got over 200. Actually the telling feature was when the fans did kick on, even while pulling, it dropped the temps down to 185 and then the cycle repeated itself. To my mind, this means the fans were more then capable of controlling the heat build up and have never worried about it since.

Even when we towed our new RV back from the dealer to home (about 120 miles) and it was obvious the 6.2 did not have the oomph to overcome the added weight (5,000 lbs) and the abysmal aerodynamics, heat was not an issue. Spent 4 hours with the pedal welded to the floor at 50 MPH and still the fans kept it under 200 degrees. Granted the outside temps were in the 50s but certainly the heat load would have been taxing the cooling system.

I can't speak to how effective the electrics would be on turbo charged engines, but they are more then sufficient for the NA varients. I see no need whatever for the mechanical fans if you can find the right electrics.

Bill

[Burbinator]

Here's something you can try, along with the thermostat recommendation although in my opinion that's a tool for tuning or temporary fix and not the ultimate solution. The larger radiator core you have is a necessity, and you can add more rows (expensive, but a definite part of the proper solution especially since this a rig with an engine swap) if needed--but too many rows will boost your coolant capacity to that point that it will begin to tax your water pump, which will in turn have a parasitic effect on power and engine peak rpm. As for general cooling, I prefer a mechanical fan over an electrical fan because of the hp gain when using a hub with a thermostatic clutch. But if space is an issue, a good electric fan, or set of fans, will do just like convert2diesel said. You can even use an electric fan to help a mechanical fan if needed. That said, what I'm about to suggest will take you a bit of time and maybe a little knuckle meat, but its what I'd do in your situation.

Your idea of freeing up the exhaust by adding larger and better piping is a step in the right direction. On the other hand, a diesel is essential big air pump--the more air you put in, the more power you get out. Free up the exhaust, and you get more air in because more air is going out (simply put), and thus more power. That increase in power is going to equate to more heat in the engine bay, and thus higher temps. On another note, an increase in ambient temperature under the hood will offset the horsepower gain as the air will be hotter as it goes through the induction system and into the cylinders for ignition. Cooler air makes more power, more efficiently.

Naturally, I don't know your background with engines and whatnot. But I can tell you from experience that if you go down into the engine room of larger marine vessels that are running detroits, cats, etc. you'll notice that the exhaust manifolds and piping are insulated. If you take a walk onto the local tarmac, you'll see the same thing on many aircraft engines and GPU's. Military vehicles show the same thing, especially if your motor pool personel are smart and know how to squeeze every last bit of power and economy out of their equipment. Finally, flip open a hood on a turbocharged vehicle--you should see some sort of insulation there if time and wear hasn't rotted it away.

The biggest source of heat in your engine bay is the exhaust manifolds, which radiate heat. Now consider that the exhaust manifolds not only attach to the heads (and the coolant passages are right there at the attachment points), but extend downward and hug the block to a degree--where the water jackets are. Before proceeding, consider the following: most people aren't aware that the main bearing webs play are very large role in bleeding heat from the engine as it is running. The heat from combustion (which is used effectively to make power or lost by the piston and rings into the water jacket) is collected and passed through the pistons and sent through the rods to the crank which, through the medium of the oil, sends that heat through the saddles and webs into the cylinder case walls and ultimately the water jacket. So really, you're not just talking about the coolant and water jacket alone; you should consider the entire system and not just a part of it. By that reasoning, you have one area that you can control effectively: the exterior of the block and those components that attach to it. In this case, that's the exhaust manifolds.

By insulating the exhaust manifolds you not only reduce the heat and radiation effect produced by the exhaust stroke, which will obviously raise underhood and coolant temperature, but also cut down on heat exposure to the cylinder case exterior, which will be absorbed by the coolant in the water jacket. It will also allow the oil and main bearing webs, and your entire reciprocating assembly for that matter, to run cooler because the block will be able to radiate heat more efficiently, which will in turn allow your cooling system to be more effective and efficient.

The method then is to yank the exhaust manifolds off the left and right banks, and take them down to your local shop and have them cleaned and blasted (that is, if you don't have the equipment to do it yourself). While they're being cleaned, acquire several cans of hi-temp exhaust manifold paint--preferably black since it really does absorb and contain heat--and some hi-temp exhaust insulation. And don't worry if you can't see the black paint under the wrapping. It'll work anyway. :D When you get the parts back, paint them with several good coats, with plenty of dry time between, and then install the insulation material. Once its all set, hang your exhaust manifolds back on the engine, and reconnet the exhaust. You're done.

If you do it right, you should see a noticable drop in coolant temp on your gauge--it won't be a monstrous drop, but you'll see it. The main point is that your operating temp range should be much narrower regardless of how the vehicle is used. As a side note, this works well on tube-type exhaust headers, too. Just make sure that you use quality paint and insulation, or its pretty much wasted effort. In this case, I'd go to a marine division outlet for detroit diesel, caterpillar, cummins, etc. and see what they recommend and carry. That's where you will find the heavy duty stuff, and that's what you want to use--not the hot rod paint and bandage wraps that sell for nothing and basically do nothing.

The added benefit of insulating your exhaust is that the contained heat will actually produce a vacuum effect in the exhaust system, so with each exhaust pulse you'll scavenge more burnt fuel and take in more fresh fuel. That equates to better economy and more power, since the incoming charge isn't going to have as much spent fuel left in the chamber during valve overlap. Another reason why you'll see a power and economy increase is because the temperature under the hood will drop, which means cooler, denser air going in through the induction system.

From there, you will REALLY see the benefits of adding a proper fan and larger radiator, and you can fine tune the system by juggling thermostats. So like I mentioned in my previous post, 190 is about right, and 210 is the upper limit. I'd shoot for consistency in the middle of this range. Too cool and the fuel won't be hot and you'll get less performance and economy. Too hot and you'll damage the engine and its components.

[bleucrew6.2]

I'd like to go with the 180 stat, but GM/Delco only has a 190. Someone mentioned a Robertshaw unit. Does this stat flow as much as the Delco design? Can I get a part #, and possible source?

Thanks!

[DmaxMaverick]

I'd like to go with the 180 stat, but GM/Delco only has a 190. Someone mentioned a Robertshaw unit. Does this stat flow as much as the Delco design? Can I get a part #, and possible source?

Thanks!

I do not recommend using a 180° stat. If this is required to keep your ECT in a manageable range, you have other issues needing attention. If the system is healthy, it will maintain 190° as well as 180°. The key is a system able to manage heat, not necessarily keep it "cool". A lower temp stat is a band-aid, not a solution.

That said, kennedydiesel.com has the RS stats in the available temps.

[66stingray]

I'd like to go with the 180 stat, but GM/Delco only has a 190. Someone mentioned a Robertshaw unit. Does this stat flow as much as the Delco design? Can I get a part #, and possible source?

Thanks!

I just replaced the original thermostat on my 82 C10. It was a 180. Mr Gasket #4367 is an exact replacement. Found it on FleaBay.

[argo]

I just wanted to post the results of my heat related experiments and refer some of you who might be interested in doing electric fans to the conclusion in this posting right here. (http://www.thedieselpageforums.com/tdpforum/showthread.php?t=37463) Note that this is for my "Jumbo" size family station-wagon application, not a crewcab 3500 dually with a gooseneck. This might fit the bill however, for some of you who may be interested in going the electric fan route.