I'm looking to buy a 96 7.3 F350 dually/crew cab, the truck was a trade in and only has 129,000 mi, but the dealer doesn't know any maint. history. I have heard that if the anti freeze doesn't have an additive in it you can get cavitation. What I want to know is how can you tell if the engine has cavitation? The truck starts easy and runs smooth.
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Only way you can tell is if anifreeze is filling the oil pan. All diesels are subject to cavitation, it would take about 500000miles to get any significant damage

 

In short...If you like it..BUY IT!! I would.........just change all the oils and coolant when you get it home.. don't trust the dealer to do it...their motto is if it looks like it needs changing they will...I personally have no idea what kind of superman visual analysis they do and don't wanna know.

 

The reason for the additive is for corrosion control. The corrsion additves get consumed over time. As long as your antfreeze is in good shape you test the additive levels and add some if required.

 

You can't tell by looking at it. It takes about 30 seconds to test the coolant yourself, swing by an International dealer and pick up some test strips.

 

Cavitation only occurs in pumps when there is not enough suction pressure or too much air.
Most Diesel engines have a problem with electrolysis, especially around the o-ring seal where the cylinder liners meet the block. The additive is there to stop this electrolysis. There is a test strip that you can buy to see if you have enough additive in the coolant to stop this. There is additive you can buy to put in your coolant if your coolant don't have enough left.
There are three test on coolant to tell if it is time to change it. One is the PH level, should be above 8ph. Your additive brings the ph back up to above 8ph. Another is the amount of visible gunk in it. Should be a clean looking green on the ethylene glycol based coolants. Antifreeze breaks down over time and should be repalced overtime, depends on how well you maintain it and how many miles you put on it. The other is the amount of corrosion control additives still in it. The test strips test this, and the additive restores it. New antifreeze properly diluted with water has plenty of additive in it and the proper PH. If in doubt change it out. Do not ever use Prestone antifreeze unless you want a plugged up cooling system.

 

firebug,
The cavitation you are hearing about is actually caused by very small air bubbles that are entrained into the coolant during it's circulation. They stick to the hot cylinder walls and when they burst they take tiny metal particles with them. After a long period of exposure to this it causes corosion on the coolant side of the cylinder and the engine will end up with coolant in the oil. The additive prevents the bubbles from sticking in the first place thus preventing the corosion. There is no way to see this without completely disassembling the engine and looking into the coolant passages. This process can take a great deal of time unless the cooling system has an air entrainment problem which is not the case with most Ford products. The additive is a good idea but not entirely neccessary. Also do not overconcentrate the antifreeze as this will cause your water pump to leak due to the cilica in the antifreeze dropping out of suspension and becoming a particulate then getting into the pump seal.

 

Cavitation has nothing to do with entrapped air. cavitation is caused by negative pressure (vacuum) this causes the water or antifreeze to boil (turn from a liquid to a gas) when the water vapor bubbles colapse they can be very destructive.

The antifreeze cavitates (boils) next to the cylinder walls because the walls are expanding and contracting very quickly. when they contract this causes a negative pressure and the gas bubbles colapse against the wall.

The SCA additive everyone is talking about creates a barrior between the cylinder wall and the antifreeze. when the bubbles colapse they impact that layer instead of your engine.

Klr2mato I don't know how prone to cavitation damage the powerstrokes are but I wouldn't buy that didn't have the diesel additive.

 

grt,
In 17 years as a journeyman truck mechanic 9 of it spent as an apprentice and journeyman at Cummins Oregon Diesel I have overhauled and done failure analysis on probably a thousand engines. Most of them were 855ci cummins or similar powerplants. All the training classes I attended in those years told me the same thing I stated. One thing I noticed was that the corosion pattern on the liners was almost always in the same place. It was on the front of the liner where the coolant entered the cooling jacket and hit the front of the liner. The air is not entrapped it is entrained or brought into the coolant flow from the outside or from turbulance. However your theory about the negative pressure makes sense in that the negative pressure draws the air together to form the bubbles. Ever filled a clear container with water and then applied a vacum? What do you get? Bubbles. I can tell you that the engines have exhibited this effect to varying extents at varying and seemingly unrelated mileages. Some of it seems to depend on the quality of the maintenance and some does not. I'm not sure anyone really knows what the EXACT cause is. I do know however that DCA does help. I also know that in our fleet of ambulances we never use ANY additive in the coolant and we have had PSD's go over 300,000 miles without any problems. They also get very good PM. So there you have it.

 

isnt cavitation more of a concern on a wet sleeved engine than a solid block? due to the make up of the liners?

 

I didn't meen to offend anyone, and klr2mato you are far more quailifed to speak to how the engines fail or don't fail. and it is quite possible the damage your seeing is caused by entrained or entrapped air. There are a number of ways for corrosion to occur. I have torn the older engines apart but I haven't see the powerstrokes.

cavitation is a word that is often misused. much like the diffrence between concrete and cement. It bugs me when its missused. If I came off as harsh or rash I'm sorry.

Cavitation is what happens when the pressure drops below atmospheric pressure and a vapor bubble forms. When it occurs in large pipes (not engines) it can be very destructive and sounds like gravel and rocks are flow through the pipe. It is also what eventually destroys propellers. Cavitation is water vapor bubbles colapsing against a surface. when this happens the force is often equivilent to thousands of psi.

I know that in my engine the pre-power stroke the cylinder walls are not as thick as they should have been. This allows them to vibrate more, creating more cavitation and since its thinner it doesn't take so long to eat through. For these engines to fail from true cavitation is not uncommon. Prehaps, the newer engines are better and the failures listed under "cavitation" here are actually other forms of corrosion.

I'm considering upgrading to a powerstroke in the future and its good to know the newer engines do not have the same problem (or at least its not as bad)

Ryan

 

either way, you can ask for a limited warranty or ask to take an oil sample. The oil analysis will cost about $20 and then if their is no coolant in the oil, you can be pretty sure that there is no cavitation damage.

 

no rust with corosion or cavatitation, with evens npt+ watterless coolant. never have to change or add addatives. you can do a oil test to see if the truck you are buying has rust problems. cost 10 dollars i think, someyone here must have the address.

 

You major source of cavitation would be from the pump impeller. As the blade moves the liquid an area of vacuum is created behind each blade of the impeller. This is the vacuum grtf250 was speaking about. Depending on the viscosity of the liquid it has to fill in the area of vaccuum before the next impeller blade compresses the area. If the the fluid is to thick and can not compensate and move into the vacuum, then the fluid comes out of solution and boils at extremely low temperatures (with considerable release of gasses). If these gasses cannot be recombined then you will unbalance the fluid and cause breakdown of the chemicals.

The bubbles coming out of solution will cause damage to just about any material they run into. Our Nuclear subs can ruin a million dollar prop in a matter of minutes with enough cavitation. The accoustics and vibrations that accompany cavitation can even tear apart a subs drivetrain and powerplant.

both grtf250 & klr2mato are correct. My guess is that the coolant pump in conjunction with not so great coolant would easily send these destructive bubbles into the pipes.

 

I would do a test with a Fleetguard test strip to see if the additive package in the cooling system has been maingained. If you go to a Navistar/International dealer they have individual packets under part number OCC2602B for around a buck. If the additives are not at correct levels it does not mean you have the damage mentioned. If they are at correct levels it does indicate you are most likely fine.

Dave / Believer45