Cavation symptoms
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Cavation symptoms
What are the symptoms of an engine that has the cavatation problem that is known for the 7.3L engines??? My 88 has a lot of vibration at idle, and I can't tell if it's actually skipping or not, which I would think would be a problem if it did have a cavatation hole in a cylinder. I have checked the injectors, loosened each line to see if the engine misses or changes speed and they checked out fine...I do not see it smoke except on start up when it has a hard time of starting, then some blueish white smoke....I do have a small antifreeze leak somewhere, as I have to keep putting small amounts in the overflow tank, but I also believe I have a radiator leak too....As I have seen it wet at the bottom of the core..It has been harder to start when cold ever since Imessed with the timing, trying to get some of the vibration and shake out of it...I do know it has some of the vibration and shake when you start from a dead stop, then it quits. Truck still has plenty of power though....How smooth do thes trucks idle??? The chevy diesel I had years ago did not have any shake or vibration at idle...I'm also suspect of motor mounts, wouldn't they also cause a shake or vibration at idle??? What's the best way to check them without removign the engine??
Post Fiend
Joined: Nov 2003
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From: Nutter Fort, WV
As long as you keep the recovery tank full, does the radiator stay full?
Unless the cavitation hole is at the very bottom of the piston stroke you usually have compression leaking into the cooling system.
That causes coolant to be blown out of the radiator.
Since the cavitation hole also lets air into the coolant passages, when the engine cools down the coolant does not get sucked from the recovery tank back into the radiator.
Another sign is sweet smelling exhaust which will be white if the leak is big enough.
Motor mounts are almost indestructable.
The originals on my 86 are still like new.
Unless the cavitation hole is at the very bottom of the piston stroke you usually have compression leaking into the cooling system.
That causes coolant to be blown out of the radiator.
Since the cavitation hole also lets air into the coolant passages, when the engine cools down the coolant does not get sucked from the recovery tank back into the radiator.
Another sign is sweet smelling exhaust which will be white if the leak is big enough.
Motor mounts are almost indestructable.
The originals on my 86 are still like new.
Last edited by Dave Sponaugle; Jul 21, 2007 at 09:05 PM.
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Just yesterday got rid of the pepsi bottle that I had been using as a recovery tank. The original recovery tank had a slit in the seam on the side opposite the fender, so after fixing that and letting it sit full of water for a while to make sure it didn't leak, I put it back on...So I'll let you know about that if a few days. I did however notice today when the truck was cold I put some anti-freeze into the recovery tank, started up the truck and noticed air bubbles coming out the hose from the radiator...I did check the radiator beforehand and it was like 1/2" below the top....Could these air bubbles just be from the space on top of the radiator, or could it be something else??? I've never seen a diesel shake like this, except a semi....
Post Fiend
Joined: Nov 2003
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From: Nutter Fort, WV
The air at the top of the radiator will come out of the tank first as the coolant warms up.
If the recovery tank has coolant in it, the radiator will suck the coolant back into the radiator.
As long as there are no leaks in the cooling system and there is some coolant in the recovery tank, there should be no air in the radiator after a couple heat/cool cycles.
If the coolant tank has coolant and the radiator has air in it, you have a leak somewhere that is letting air into the system.
Cavitation, cracked block, cracked head, blown head gasket will usually put enough pressure into the radiator to blow the recovery tank lid off.
If the recovery tank has coolant in it, the radiator will suck the coolant back into the radiator.
As long as there are no leaks in the cooling system and there is some coolant in the recovery tank, there should be no air in the radiator after a couple heat/cool cycles.
If the coolant tank has coolant and the radiator has air in it, you have a leak somewhere that is letting air into the system.
Cavitation, cracked block, cracked head, blown head gasket will usually put enough pressure into the radiator to blow the recovery tank lid off.
Elder User
Joined: Feb 2007
Posts: 549
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From: Mississippi
make sure the line that goes from the radiator to the overflow bottle is sealed as well. mine has some slack in it (not tight enough) and on occasion when i load it heavy and run it hard, will push some coolant out. i'm sure that's not what's causing the shaking problem, just another leak site to check.
speedrdr
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Cavitation symptom
I have a simular situation: Within seconds after I start my truck, water starts boiling out of the radiator and over the storage tank lid. My aftermarket temp sensor shows the water circlulating through the system after the water hits about 200 degrees F. My original thoughts were a T-stat or water pump but since I have circulation I then thought cracked head gaskit, but I check the oil, exhaust, and did a compression check and everything seems normal. Is it posible to have exhaust getting into my coolant without these other symptoms or is there something else I can check. Diesels are a bit new to me, but before I bought a newer one I thought I should figure out the basics on a older one first. Any advice is greatly appriciated.
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From: KY
If you have a cavitation hole it will very likely hydrolock on one of these engines because the piston is flat. Most of the time coolant will not drain into the crankcase because there is carbon that has filled in the ring gaps. That isn't always the case but it is very likely.
Like somebody mention, keep your coolant additive up to date. You can't stop the cavitation but the additive coats the block to give the air bubbles something to beat on instead of your block.
Like somebody mention, keep your coolant additive up to date. You can't stop the cavitation but the additive coats the block to give the air bubbles something to beat on instead of your block.
Post Fiend
Joined: Nov 2003
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From: Nutter Fort, WV
carttim,
Welcome to FTE and the IDI diesel forum.
Cylinder compression can get into the coolant passages without going to the oil.
Also coolant does not have to show up in the oil when that happens either.
And sooner than later if that is the problem, the engine will hydrolock.
If you try to start the engine and it does not want to turn over, stop right there before you break something.
Welcome to FTE and the IDI diesel forum.
Cylinder compression can get into the coolant passages without going to the oil.
Also coolant does not have to show up in the oil when that happens either.
And sooner than later if that is the problem, the engine will hydrolock.
If you try to start the engine and it does not want to turn over, stop right there before you break something.
New User
Joined: Jul 2007
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Thanks
I will try adding more chemicals. When I bought the truck, I new I needed something for the coolant system so I went to to the dealership and used what they recommended. Hopefully I don't have a cracked block or head we'll see
Thanks
Thanks
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