Diesel owners...To cover or not to cover?

[FlatBottom]

I've got myself an 02 f350 7.3. Driving down the road I see maybe one in two/three trucks(diesels) that have some form of grill cover. My question is, is there any benefit or lack there of for covering the grill? I'd guess it would help with heating, but don't you need some air flow?? Just wondering. Thanks.

[pureinsanity]

Well, Im no expert. But I think it is simple logic. The grill cover just helps to hold the warm air under the hood and allows for a faster warm up when at idle. Hence why diesels have a higher idle when sitting in one spot. If you didn't have a grill cover you will just idle higher because cold air is being sucked in through the grill. It restricts the flow of cold air your fan can pull.

Once your vehicle reaches operating temp, your thermostat regulates the temp from there. But the bra just helps to hold the warm air under the hood and warm up faster?

If that makes sense?

[LMITOUT]

A cover doesn't hold the heat under the hood as much as it prevents it from flowing through the radiator(s) when driving.

Diesels have excellent cooling ability which is great for summer but no so much this time of year. In temps like these you can cover the grill entirely and not have any issues with overheating. When it gets around 30 degrees outside I'll peel my grill cover off, but the transmission temperature is affected more than engine temp at that point. The tranny cooler seems to need more airflow on my truck (Duramax), although the transmission cooler is quite a bit smaller than the engine radiator.

I use the factory grill cover and I fold the upper left and right hand corners down and tuck them behind the cover before I snap it in place to allow some airflow through the grill.

[BobT]

I have never really quite understood grill covers. Your engine temperature is controlled by a thermostat and if it is working properly, I would think it should be controlling fluid flow in order to maintain operating temperature.

The one thought I have had with diesels is that diesel fuel is prone to gelling. This can happen for #1 as well as #2, just at different temperatures. The gel point for #2 is somewhere around -5 to -10 degrees and #1 is somewhere below -40 degrees.

Wind chill does not cool diesel fuel below the air temperature BUT it does determine how quickly the fuel can cool to that temperature. Many truckers continue to run #2 at temperatures at or below the gel point but because the fuel is being heated by the return lines and in some cases by external heaters, they can get away with this. At highway speeds however, the air flowing through the radiator can have a tremendously low wind chill factor and this can draw heat out of the fuel fast. For example, #2 might gel at -10 degrees. If a truck is running the fuel in the tank might be held a little above this point as the heated return fuel keeps it warm. The fuel in the lines however could get rapidly chilled down to the air temperature as the air comes in past the radiator and this might cause it to gel in the lines. Covering the grill reduces the amount of air flowing directly in and this keeps the engine compartment a little warmer. This is my guess anyway.

[LMITOUT]

I have never really quite understood grill covers. Your engine temperature is controlled by a thermostat and if it is working properly, I would think it should be controlling fluid flow in order to maintain operating temperature.

I can let my truck idle for long periods of time in temperatures such as today and the engine will barely get over 100 degrees (normal operating temp is around 180). The cooling system is just that much more efficient on diesels, hence the reason for the higher idle setting to get some heat into the cab.

I don't believe the engine cover has any bearing on the fuel temperature. If it does I would think it would be minimal. My truck has a radiator near the tank which is used to cool the fuel before it returns to the tank. The high pressure injection systems create so much heat in the fuel that they have to cool it down.

The programmer I installed can monitor the fuel temp but I'm not sure where that reading is taken. I'd like to know just to have a reference of what it actually means.

[311Hemi]

I don't believe the engine cover has any bearing on the fuel temperature.

I agree. The covers are not to keep fuel warm or from gelling, but to keep cold air out of the radiator and engine bay. This will allow the truck to warm up faster and retain heat better.

[pureinsanity]

The covers are not to keep fuel warm or from gelling, but to keep cold air out of the radiator and engine bay. This will allow the truck to warm up faster and retain heat better.

That is what I said as well, but I guess I shouldn't have used the words "keep warm air under the hood."

[BobT]

I don't think the the higher rpm on diesels is because the cooling system is so efficient. It's the engine that runs efficient and at an idle won't generate enough heat to heat up the coolant, especially if you run your fan to defrost windows and heat the cab.

If the engine isn't heating up, the engine thermostat stays closed and no fluid flows through the radiator core. A grill cover in front doesn't matter if the coolant isn't flowing through the radiator.

[LMITOUT]

I think we're saying the same thing.

[BobT]

Oh.

[swamptiger]

As Limit said, the diesels have a better cooling system, so a lot of them won't really reach proper operating temps in cold weather, especially at idle. So the grille cover just helps them maintain operating temperature. If the engine runs too cool, it will burn more fuel. Also, diesels running too cool don't burn the fuel efficiently, so the raw, unburned fuel can wash the cylinders, causing premature engine wear. There's a good reason you see a lot of big diesel rigs running grille covers.

[dougger222]

Never put covers on my diesels. Overheated a few times with the plow so try to keep the front as open as possible.

Air on the Ford diesels gets through on the small "snorkel" on the driver side of the grill.

[pureinsanity]

Never put covers on my diesels. Overheated a few times with the plow so try to keep the front as open as possible.

Air on the Ford diesels gets through on the small "snorkel" on the driver side of the grill.

Gotta drive nicer jk. Over heating is no fun. Snow as light as it is, is hard on equipment. Only time I almost over heated was when the water pump in the skid loader decided to shred apart. Luckily the fan blades didn't puncture the radiator.

[Valv]

Air on the Ford diesels gets through on the small "snorkel" on the driver side of the grill.

That's engine intake, the snorkel funnels air to the air filter.

[FlatBottom]

Thanks for all of the insights. Now this may make little sense, but by blocking the airflow, is it harder on your fan/bearings/waterpump etc? I mean take your 20 inch box fan and put a piece of cardboard on the backside, eventually I'd think the fan'd work to hard and burn out. Or doesn't it work that way? Thanks

[pureinsanity]

Thanks for all of the insights. Now this may make little sense, but by blocking the airflow, is it harder on your fan/bearings/waterpump etc? I mean take your 20 inch box fan and put a piece of cardboard on the backside, eventually I'd think the fan'd work to hard and burn out. Or doesn't it work that way? Thanks

If you put the cardboard to the back of the fan yes. Hold it a few inches away and it wouldn't matter. The covers are not restricting the fan much, if at all.

[BobT]

The grill skirt covers the grill, not the radiator. There's some distance between the grill and the radiator that still allows air flow, just not directly through it.

[swamptiger]

Quote:

The grill skirt covers the grill, not the radiator. There's some distance between the grill and the radiator that still allows air flow, just not directly through it.

Yes - it's not a good idea to put cardboard or anything right next to the radiator because it can cause the engine to overheat very easily. I've even heard stories of the fan getting sucked into the radiator by doing that - don't know if that's true or not.

[311Hemi]

The grill skirt covers the grill, not the radiator. There's some distance between the grill and the radiator that still allows air flow, just not directly through it.

Not for the Cummins. Below is a pic of the one that Dodge sells. Also, many guys with the Cummins use cardboard or other homemade covers that are located direct in front of the radiator. (EDIT: I don't know if completely covering the radiator can cause issue to the fan clutch, some guys have made mention that it could overhead and cause additional wear). I can't speak to the other brands.

I personally just mount a plastic cover to the grill, but not sure it really helps a whole lot.

[swamptiger]

That's right up against the radiator? Is there screen or mesh or something in the opening?

[311Hemi]

That's right up against the radiator? Is there screen or mesh or something in the opening?

There is a mesh opening in the middle that you can see in the pic, and there are 4 flaps that can be opened/closed as needed.

This is obviously in front of the intercooler/trans cooler/radiator, but I don't know if it is touching the intercooler which I think is the first big cooler (most forward). I think it's pretty close and would when driving at any speed. From the sounds of it it connects to the bumper on the bottom which leads me to believe there is an open area to allow for some airflow. I don't own one so I can't say for sure.

A lot of guys drop cardboard or some other material between the intercooler and radiator.....thus only blocking the radiator. Again, I don't know if this can cause issues with the fan, but some say to cut a certain size hole in a measure out location to keep the clutch cool. That's just info I got off other forums when looking into this in the past.

When doing any heavy towing I would certainly question blocking the radiator.

[swamptiger]

My experience is you need at least some airflow in order for things to work properly. Sometimes people can get by with putting cardboard directly in front of the radiator if they cut a hole in the center to allow some airflow. Maybe there is enough room to get some airflow through or around that unit - looks like a nice accessory.

[Valv]

First large radiator visible is the intercooler, then we have a large gap then AC condenser, then a very small gap (1/2"), and finally the radiator.

If you put cardboard you can only put it in the large gap between intercooler and AC condenser, also if you use AC while driving the condenser will heat up and warm up radiator too.

[Powerstroke]

Yikes! Lots of interesting discussion, but very few facts on this one.

Diesel engines idle up to prevent wet stacking (the cylinder washing mentioned before. Unburned fuel begins to accumulate in the cool cylinders and can cause damage) HIgh idle also helps warm the motor to operating temp sooner. Although getting heat faster is a byproduct it is not the reason. Also heats up the cylinders for better combustion.

Covering the grill is not necessary, but it can be helpful and beneficial. Lots of systems combine to help the engine reach operating temp and if the engine never gets there than the motor is constantly compensating by adding more fuel and using exhaust gases to heat the engine. Ford's do this with the exhaust backpressure valve. Its the chugging commonly heard when you let off the accelerator.

Diesels are most efficient when they are as warm as they can be. If your diesel is never warm then its not working to its full potential. Monitor your coolant temps and see if its an issue for you.

Right now my truck is barely hitting 180* when I'm driving this cold. My mechanic at work things the thermostat is sticking open so I plan on replacing it. Most of the discussion on a certain powerstroke forum says I should easily reach 187-192. I may also place some cardboard inside of the grill to reduce the airflow over the radiator.

Seeing as none of the covers are welded on, I would think its a worth experiment. If you begin to overheat then remove part or all of it. If not, then you're fine. If you feel like your fan is coming on too much then that might be a sign too, but in general if its below freezing, it might actually help your diesel perform better.

[Powerstroke]

This is one of the few times when I wish I could link info to another site.