I hate to compare.... Chevy 5.3 vs Ford 4.6

[Larryjb]

Lots of variables here as mentioned. All the little differences can make huge impact on a Max effort climb like the Coq. Tahoe at least 300 lbs heavier according to Google.

Definitely the weight would have been a factor, but that's impossible to control unless I decide to bring both vehicles, go up and down the Coq with one, then hitch the trailer, move all our gear to the second vehicle, go up and down a second time. Sorry, I'm just not going that far with this to prove my casual observations!

Tahoe 6 years older vehicle, how was condition of the cooling system? Fresh coolant, newish pump, radiator not restricted from external debris or internal corrosion etc etc. Poor old Tahoe...

I wouldn't have gone up the Coq with such a bad cooling system. I have read about other's experiences where the temperature would rise a little towing up a hill like the Coq, so it does seem that the cooling system on the older Chevy's do get quite warm. However, you cannot rely on the gauge to know what the temperature is. The Scangauge is far superior to monitor the temperature. Poor old Tahoe.... don't forget these Tahoes live long healthy lives if taken care of.

Going up grapevine, our 6 speed Toyota SUV don't hunt as much for gears compared to our 2002 Yukon...that 3/4 hunt is annoying... usually have to keep it in 3rd manually so I don't wear the 2-4 band premature.
Happy New year!

Why don't you use the Tow/Haul mode on the Yukon? These new 6, 8, and 10 speed transmissions do a lot for drivability. I think Swathdiver is right, the 6 speed automatic and VVT are probably the big differences. One other difference that you might not know of unless you have one of these Fords, the newer cooling systems operate at 20 psi instead of 16. I've been curious if this increase of 4 psi is enough to allow more heat to be absorbed by the cooling system without a temperature rise.

 

[afpj]

The onboard coolant temp gauge definitely inaccurate. During summer climb over grapevine, the dash gauge stayed below 210, but torque pro would show 215+. As far as 3/4 gear hunting, yes, tried the towhaul, but wouldn't make a huge difference. The Corvette servo made the biggest difference by far for holding gears. Got 198+k miles and plan to keep 'er going!

I had no idea about higher pressure cooling system...is that just Ford?

 

[RET423]

Firdtly, 212 degrees is not "hot"; that is about what the thermostat is set to run at on a 5.3

Secondly, the Grapevine is between 5 & 6 percent at the steepest points Southbound and 5 percent is the maximum pull Northbound; I am not familiar with the other grade you mentioned but if it is 7 percent or more as you indicated then it is a MUCH harder pull than the Grapevine.

 

[swathdiver]

The onboard coolant temp gauge definitely inaccurate.

The coolant temperature gauge is purposely made to stay at or near 210 over the normal operating range of temperatures so as not to worry drivers and clog up the dealerships.

 

[TheAutumnWind]

What transmission cooler is each vehicle running? If the Hoe doesn't have an external cooler and the trans is hunting for gears you will definitely see a temp increase.

That being said ~212 degrees is not something I would be concerned about.


This sounds to me like one vehicle is better equipped for this sort of thing, and has nothing to do at all with engine differences.

I'd take a 5.3l over a 4.6 anyday based on reliability and maintenance, but the 6 speed is definitely superior to the 4l60e.

In stock form the 4l60e is a decent trans for a car, but in the trucks they are inadequate if you intend to do much towing. vette servo and improved cooling go a long way to help longevity pretty inexpensively.

In addition your old Hoe has a mechanical fan and probably one of the smaller radiators. You can swap to a HD rad and electrica fans.

 

[Larryjb]

afpj: The 20 psi cap on the Ford will only provide a higher boil over protection. It won't provide any significant extra heat capacity. In fact, since the trip to LA, I replaced the cap with a 16 psi cap to reduce the stress on the radiator gaskets.

RET423, the grades on the Grapevine vs the Coq are similar. The main difference between the two of them is the Coq is much longer. When I went up the Coq, the temperature gauge on the Tahoe began to rise when I got to the steeper parts. But, in general, even in the steepest portions of both, are similar.

Swathdiver, when I saw the temperature gauge rising, that got me worried because I knew it wasn't accurate as we know, and I didn't know how high it could go without boiling over looking at the gauge. I just knew I didn't like the trend. The biggest reason I won't take the Coq again is that it is 4 lanes (2 each way), and a narrow shoulder in many parts. If you have any breakdown, you will be partially blocking a lane where cars may be approaching at 70 or 80 mph. That is a death wish. I know some one who was killed changing a trailer tire.

AutumnWind, Yes I believe the 08 Explorer is better equipped for towing. I can sure say I feel the difference with VVT. My Grand Marquis had pretty good acceleration, but not as good as my 5.3 Tahoe. The same engine in the Explorer with VVT and a 6 speed auto, it is at least as fast as the Tahoe, and seems to have better pulling power. The Tahoe is better equipped for our stuff though. The cooling systems of each vehicle are fragile: the Tahoe has those nylon "Y" fittings, the Explorer has a pipe snaking within inches of the exhaust manifold, and has its versions of nylon "Y"s. As for reliability, I had a 4.6L in my 1992 Grand Marquis. I sold it last year because I didn't have room for it in my driveway, but with nearly 250000 miles, it was still going strong. The only reason I had to change the water pump and radiator was that I neglected to change the coolant once and it went acidic on me. 6 months after I changed the coolant, both radiator and water pump went on me. The big difference, as I said before, is that the 5.3L (at least in 2002) is much simpler to work on. Overhead cam engines are a pain, and with VVT even more of a headache to work on.

I would love to try a new Tahoe with VVT and the newer transmission, even if I can't afford to get one. I'm sure that would make a huge difference.

Another reason the Explorer is nice for travelling is that it is much quieter. I could add insulation to the Tahoe, but I have other things I have to spend my money on.

 

[TheAutumnWind]

AutumnWind, Yes I believe the 08 Explorer is better equipped for towing. I can sure say I feel the difference with VVT. My Grand Marquis had pretty good acceleration, but not as good as my 5.3 Tahoe. The same engine in the Explorer with VVT and a 6 speed auto, it is at least as fast as the Tahoe, and seems to have better pulling power. The Tahoe is better equipped for our stuff though. The cooling systems of each vehicle are fragile: the Tahoe has those nylon "Y" fittings, the Explorer has a pipe snaking within inches of the exhaust manifold, and has its versions of nylon "Y"s. As for reliability, I had a 4.6L in my 1992 Grand Marquis. I sold it last year because I didn't have room for it in my driveway, but with nearly 250000 miles, it was still going strong. The only reason I had to change the water pump and radiator was that I neglected to change the coolant once and it went acidic on me. 6 months after I changed the coolant, both radiator and water pump went on me. The big difference, as I said before, is that the 5.3L (at least in 2002) is much simpler to work on. Overhead cam engines are a pain, and with VVT even more of a headache to work on.

The 4.6L 2v in your 92 grand marquis and the 4.6 3v with VCT in your 08 Explorer are not the same engine.

The latter likes to shoot spark plugs through the hood, and cam phasers like to fail.

I had a 99 F150 4x4 with a 5.4L that was a great truck btw.

 

[Larryjb]

I realize they're not the same engine, the same way the 5.3L in my Tahoe is not the same engine as what's in the current 5.3L. I believe that by 2008, the spark plug issue had been fixed. What can be an issue is spark plugs snapping off when trying to change them. There is a tool available to remove such a plug. As for blowing out spark plugs, there had been issues with spark plugs getting shot out from the Grand Marquis, and from the 5.4L as well. As I recall, as long as they're installed correctly without antiseize, and torqued properly, they're fine.

I'm hearing that the cam phasers and timing chain guides fail if strict oil changes are not followed. However, replacing the phaser and chain guides, while annoying, is not too bad. Replacing lifters in the 5.3 involves a fair amount of work as well. All engines have strong and weak points. Both GM and Ford have been pretty good with the V8 engines. I wouldn't get a NA V6 from either Ford or GM though. While the latest 3.8L in my last Buick was not bad, the transmissions in those were terrible, and GM never fixed the problem that caused it.

The 4.6L in our Explorer now has 170000 miles on it. There is no sign of phaser problems or timing chain guide wear. I keep up with regular oil changes using synthetic oil and a catch can.

Overall, the Explorer has been a great vehicle for my wife, the Tahoe is great for me.

 

[RET423]

RET423, the grades on the Grapevine vs the Coq are similar. The main difference between the two of them is the Coq is much longer.

I just googled Coquihalla Pass and the highway department reports the steepest parts at 8.5 percent, this is much, much steeper than any part of the Grapevine and is most definitely not a valid comparison to judge which engine is performing better.

 

[RET423]

I guess I should explain why I posted that info about the different specs of these two grades beyond the obvious.

VVT is primarily used to eliminate the need for an EGR valve to meet emmisions and economy standards, the valve overlap is altered so the time that the exhaust valve is opened during the intake stroke is slightly increased which allows exhaust gasses to be sucked back into the cylinder as the air/fuel mixture is being sucked in through the intake valve, this is done as the engine computer deems necessary; this task is performed by the EGR valve on your 2002.

When exhaust gasses are introduced they provide "cooler combustion temps" but that is not the same thing as "cooler engine temps"; it just means the polluted air/fuel mixture burns slower due to having less clean oxygen to assist in the burn.

For this to translate into a cooler running engine would require a cooling system in extremely poor condition as this reduction in combustion temps is very slight.

VVT can be used to alter valve timing to increase performance as well in race applications but on a factory vehicle it is used primarily for emmisions control.

I would not consider VVT as a desirable feature for any vehicle that tows a heavy load, when it works it is probably slightly preferable to an EGR valve but an EGR valve can be serviced easily without dismantling the engine; a problematic VVT requires major surgury to service.

The ideal for Towing and performance is neither system, just cool clean air in every combustion cycle and a fuel curve designed for only clean air and fuel.

The 5.3 vortec in your Tahoe will dust your smaller ford in any apples for apples comparison if both engines are running correctly.

Also the LS series of GM motors is the most efficient cooling scheme that I have ever encountered in a V8 engine; even when built to immense power levels in race applications they are very easy to keep cool.