2002 4.7 4x4 Quad Cab sport

Bought used- 265k

Two weeks ago my truck overheated - the same day it had a rough start (low rpm) but stepped on the gas it seemed to be back to normal. Got home, and my coolant reservoir was about empty so I refilled it and everything seemed fine.

Last week - overheated again. Reservoir was down just a little, so topped off. Had another low rpm start the next day - and coming to idle while driving it would dip down to a lower rpm. By the time I got home it was overheating again. Reservoir was pretty full.

I parked it - got a radiator pressure test (pump) and got it up to 20 psi with no sign of leaks.

I go to start it - and now zero to extremely low oil pressure. I check the oil, it’s full (a tad over). Open the oil cap (inlet) and notice a slight orangish/green color residue under the cap. Seemed like radiator fluid. I used green coolant , not sure what was in it before.

What could it be? Guessing a head gasket failure, but the zero-low oil pressure? Oil pump? Inlet tube or screen clogged?

I emptied the oil last night and it looked pretty good. I did notice a real small amount of white stuff within the oil - couldn’t tell if it was a liquid substance or more of a solid material (like dusty).

I paid a few grand for the truck - so fixing it myself is a must. Seems like a heck of a job getting to the head gasket and also dropping the pan (4x4).

K-Seal? Seafoam? The combination?

Any thoughts or ideas are welcome

 

The orangish buildup on the cap is normal on the 4.7 while the green is not. The reason for the low RPM start was likely water getting into the cylinder. When coolant mixes with oil it often will dislodge and gel chunky bits. Your zero oil pressure is probably from that or a convenient pressure switch failure. Also the oil won't milkshake till there is enough water mixed in so that's probably why it looks normal. I've heard of some people having luck with headgasket sealer. Might give it a try. Make sure you have oil pressure first. You can get a tester from a parts store and pull the pressure switch and insert it there. If you have oil pressure then get clean oil and distilled water into the system. Add the sealant to the coolant and get it up to temp multiple times. Check the oil each time and replace it if it gets watered down. If that doesn't work then your looking at a headgasket job or rebuild.

 

Very informative response - thanks!

For the test to work accurately, does the truck need oil? I emptied it yesterday. Ill buy a switch. I gotta find the correct pressure for this engine, maybe it’s in the manual…

If the test shows little to no pressure - I’m sure it could be a host of things, but a major gasket fail I’m guessing? Any other common issues? I guess I’ll cross that bridge after I test it.

appreciate ya

 

Rent a block tester (free when U return it). Look up vids on YouTube on how to use. Sniffs coolant for exhaust gases and is a sure fire way to detect a blown hg. Drain a pint of coolant before using.

Also if you start cold with rad cap off and coolant shoots up or is turbulent. Well u know the story.

I fixed a small hg leak chemically many. years ago. Been good since. Don't use the stuff you add to coolant. It will eventually block the heater core. Figure out where u stand then I can elaborate more if needed.

BTW....true zero oil pressure would have your engine making a racket. The same place you pull the oil pressure switch from is where you hook up an oil pressure tester. This is just above the oil filter.

 

You will need it filled with oil. 40PSI at idle is around what your looking for. Also the gauge on the dash is not an accurate measurement. Its just a simple on or off with a couple levels. If the test shows less than 30 you have either a blockage/restriction before the oil pressure switch, or a bad oil pump. Did the engine sound really rough when it was running? If not you almost certainly have atleast minimal oil pressure and its just a bad gauge or low pressure. The oil pumps on these are pretty good so I'm not expecting that. I would be betting on a bad switch. They are the more common failure.

 

I’ve started it twice - first time I don’t think the oil pressure gauge moved at all or maybe minuscule. Second time it moved up a little, but still in the very low to zero range… but the engine did not sound bad. Nothing out of the ordinary. I’ll check the oil pressure, change the switch, and get back with ya

 

I had similar problems with over heating as you described. After extensive troubleshooting, it turned out to be air gaps in the coolant system. The cooling system needs to be void of all air.
There is a bleed off plug located where the top radiator hose goes into the top of the motor. Before tearing things apart, I would 1st try bleeding the air out by removing the top pressure cap on the hose, and then the bleeding off plug, then with the engine running let the coolant circulate and adding coolant as needed until there is no more air bubbles in the system. Then replacing both the pressure cap and bleeding plug.

 

Jacking up the front end or driving it up on ramps, makes this a much easier process. Air bubbles rise and if the front is lower than the rear, the air never leaves.

 

I’ll give that a try, thanks! Hopefully that’s all it is. I rented a block tester last night to rule out or confirm head gasket failure…gonna check that today.
Let me ask - I saw a vid where somewhere said the coolant needs to be the orange stuff, not green - that the green coolant leads to problems - have you heard anything about this? I currently been topping it off with green coolant.

Appreciate it

 

I don't think it really matters which you use...... However, MIXING them is a major no-no. It tends to turn the coolant into jello..... which doesn't pump very well.