I read somewhere that cavitation is caused by the fact that diesels compression vibrates violently causing rapid changes in pressure in the coolant passages and that's the root of cavitation (not corrosion).
I've also read that cavitation really only happens in diesel engines that have cylinder liners (sleeves) to expedite changing a bad piston. They say that because the liner isn't actually part of the block, it doesn't offer enough structural integrity to prevent rapid flexation, which causes cavitation.
Apparently ALL Volkswagon diesels DONT have liners and only Cummins bigger than the 5.9s DO have liners. Since this is a Ford forum, I've also read that our 7.3s DON'T have liners and therefore DON'T need SCAs added to the coolant because the walls are thick enough to resist flexing rapidly enough to cause cavitation.
I've also read that our beloved 7.3s DO have a history of cavitation, so I'm not exactly sure who to believe?
Are 7.3s sleeved or not?
If they aren't, are the walls thick enough to prevent cavitation, or do I/we still need SCAs?
Thanks!
Last edited by Fluxcore : 07-17-2008 at 04:53 PM.
Reason: typo
The NAPA commercial duty coolant is low silicate and can be purchased in ethylene glycol. However, it does not contain SCA and you would need approximately three pints for an initial charge. After a few weeks you could test again and see how much as dropped out and if you need to add any additional.
Regarding Evans, what they don't tell you is that there is a large difference in viscosity in the Evans coolant, which is fairly hard on your water pump. Evans even makes specialty water pumps for many applications because the stock water pumps will not keep up with the circuit time needed for effective flow rates. Unfortunately, they do not make water pumps for Ford Truck applications. There are Evans products that have lesser viscosity differences than others, and are also rated with less effectiveness. But, all of them are substantially thicker than anything stock.
NAPA Kool is a surface tension modifier that will release any liquid to smaller particles. They go by many names, and they will work to some degree. They are not the end all of additives that will make all your problems go away, but they don't cause any damage either. If you use the right coolant you shouldn't have any problems, and adding a surface tension modifier doesn't hurt and might help depending on what you think of the science behind it. However, it is not SCA.
444-4D is correct. In stock format, none of the 7.3L engines come stock with sleeves. However, they do make sleeves for them and it would not be uncommon to use a sleeve if the repair calls for it. And, you still need to use SCA to compensate for cavitation damage.
jstrauss is also correct. It is a confusing subject. However, it doesn't need to be. Just don't go by the color of the liquid. Read the label and determine for yourself if it is the correct product you want to use.
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Thanks for reading, Dale Pics 1995 F350 - To much stuff to list,
more money spent than I want to admit.
There are all the pictures from the engine tear down. They are in the article too a bit. Anyways, 7.3L IDI do indeed cavitate and do it fairly quickly. 100,000-150,000 miles without SCA protection and you could be screwed.
I actually need to go an reword some of the explanation to the cavitation. When I go back and reread it after all this time I don't really like it. I think a phase diagram along with the engine animation would be the best visual aid.
If they aren't, are the walls thick enough to prevent cavitation, or do I/we still need SCAs?
Thanks!
Nice analytical deduction, but it has a problem. The 7.3 is not sleeved and does need protection. This block in 6.9 form soldiered on for many years of trouble free service. Then they bored it out, thinning the cylinder walls and creating this problem.
Cavitation wasn't even known until just a few years ago so you can drop the wet/dry sleeve analogy. The first 7.3 I ever saw was helping a friend in 1994 rebuild the engine in his 1989. He is a service adviser and was at the time. Back then the official theory was casting flaws with sand somehow trapped in pores gradually falling out causing the leak. IIRC
This is an excerpt of an article on the subject I have:
Q: What is the history of cavitation?
A: From what I have heard the first people to realize cavitation was happening inside an engine was CAT. Supposedly in the 80's they started a study about cavitation. They were the ones who came up with SCAs and ways to protect high compression engines from damage. They discovered more heat and pressure in the cooling system actually slowed cavitation. On their engines that were run with smaller loads failed sooner than the more heavily worked engines. Also, if the engines were allowed to cool down more often they failed more quickly. Ford apparently didn't know about cavitation until the late 90's. My truck is a 92 and not in one place in the owners manual does it mention cavitation or any special coolant to use. A few years after having to replace the engine due to cavitation they sent us a letter in the mail alerting us to put SCAs in our coolant to avoid damage. In fact, I still have this letter and it is dated January 1998.
No offense, but that article's full of holes. Cavitation (liner erosion is the proper name in the real world) has been around ever since there's been big diesels. I can't count how many pitted liners we changed in Cummins NTCs, etc, way back in the '60's and '70's+ due to erosion. Most all heavy diesels had Perry Filters on them to prevent the problem, but many drivers would neglect changing them. If I remember right they were made by Penray, now called Nalcool or maybe Pencool. Coolant additives have been around for decades too.
And the one and only engine I did see in person with cavitation (Ford) WAS a 6.9. It was in about '92 and the truck was torn down in an IHC heavy truck shop. I'd heard vague rumors of it happening and went in to ask the service manager if there was any truth to it. The Ford dealer wasn't aware of it at that time, but I started adding Fleetguard real quick-like. Evidently the 4.9/7.3 Navistars in a commercial application came with a factory SCA filled coolant filter like most diesels but Ford deleted them in the Ford diesel pickups---not good.
Quote:
A few years after having to replace the engine due to cavitation they sent us a letter in the mail alerting us to put SCAs in our coolant to avoid damage.
Right, and then what frosts my butt, not only was it Ford's screwup, but then they charged people twice as much for the SCA as any local truck shop.
NAPA Kool is a surface tension modifier that will release any liquid to smaller particles. They go by many names, and they will work to some degree. They are not the end all of additives that will make all your problems go away, but they don't cause any damage either. If you use the right coolant you shouldn't have any problems, and adding a surface tension modifier doesn't hurt and might help depending on what you think of the science behind it. However, it is not SCA.
NAPA Kool is relabled Wix Cool. It is a nitrite based SCA that is very similar to DCA-2.
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service adviser and was at the time. Back then the official theory was casting flaws with sand somehow trapped in pores gradually falling out causing the leak. IIRC
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