Can flushing the cooling system make a borderline head gasket blow?

[Slomo]

First I believe my manners failed me. I never introduced myself in previous threads. I have been a Toyota fanatic for years with experience mainly in 1st gen. 4runners and 2nd gen trucks. I am new to the Land Cruiser and love it. I have been lurking for about 8 months but recently took the plunge. I am so glad to have found this forum.

I have been through the FAQ extensively on the topic and searched without luck to find the answer to my problem. Yesterday I started a cooling system overhaul with a flush on my 97 with 128k miles and the original HG, thanks to e9999's FAQ thread. First drained, changed the PHH (Thanks Houston FZJ80), hooked up to and flushed the 2 heater circuits with the valve open, then flushed the block and radiator. Minor grey sludge in Toyota red coolant, no visible exhaust particulates or buildup, the radiator looks pristine. Not sure of the PO's maintenance. He talked of great maintenance but did not have the paperwork to back it up. I flushed the entire system a second time this am and was preparing to flush with distilled to then refill with fresh Toyota red and distilled. I did not use a pressure guage as e9999 recomended :whoops: but I only turned the hose on a little to not blast the pressure.

While the engine was running about 6-7 minutes into it I noticed allot of large air bubbles coming out of the radiator cap, too many. upon leaning over to look at the exhaust there was too much steam and water drops for the weather conditions. Now filled with dread I checked the oil and.... you guessed it a few milky droplets. Minutes later I rechecked to make sure that I didn't pick up water off the end of the dipstick tube as some had splashed around the engine compartment off the fan(yeah right) and there was more than before. I shut the engine down and there she sits. I just did the second oil change last week with Mobil 1 and it looked great. It has not over heated ever during my ownership and ran great until this am.

So did I pull a bone head and put too much pressure on an already weakend HG or is it a coincidence that the HG blew in the last week? Could the flush have cleared a buildup of coolant residue and opened the flood gates? I don't want to make the same mistake again.

Lastly big thanks to IdahoDoug for the HG DVD on its way, Romer for putting together the FAQ, and to Cruiser Dan for saving my ass with all the parts I needed and would have needed later because I didn't know better when he was swamped today.

 

[IdahoDoug]

Mo,

A flush can cause significant thermal stresses if you refill a hot engine, or run it while filling it, etc. No way to guess on that.

Regarding turning on the hose just a little to lessen the pressure. Dunno why you made the comment, but if it enters into what happened be advised that house water pressure is too much for the cooling system if you were using some kind or threaded on fill system (vs open system and filling the rad through the open neck). Hydraulic pressure of a hose will go right up to the full pressure even if it's only cracked open a bit. Flow is reduced that way, but pressure is not.

So, no real conclusion here but a flush can involve some rapid cooling of the internals.

DougM

 

[Slomo]

IdahoDoug,

Thanks for the input. I forgot to mention that the engine was completely cooled down and hadn't been started for about 6-7 hours with both flushes. I also filled through the heater return line that goes to the thermostat housing with the radiator cap off. I waited to start untill it was full and coming out of the radiator neck. Then I started and ran the engine with the water flowing and the radiator cap off.

I only mentioned turning on the water slowly and a little because I was not sure if a water hammer type thing could happen or the water flowing in suddenly in great quantity could overwhelm any of the gaskets. I was thinking that slow flow with the radiator neck open would not increase the pressure too much but if it hit a bottle neck in the system the pressure could spike. After reading your post and thinking about it I might have turned the hose up higher than I originally thought.

I figure the HG had to be close to failing anyway. The real bummer is that I lost a week old fill of Mobil 1, filter and most of a day battling with the PHH. Oh well, at least this way I can learn from my mistakes and get to know the 1FZ intimately. Curious to see the #6 area of the HG.

Thanks again,
Mo

 

[tarbe]

Sounds like you were smart about how you did your flush. No bonehead move that I can see.

Sounds like you were ready to blow anyway and perhaps the flushing just sped things up a bit.

 

[ElJefe]

Mo,

unno why you made the comment, but if it enters into what happened be advised that house water pressure is too much for the cooling system if you were using some kind or threaded on fill system (vs open system and filling the rad through the open neck). Hydraulic pressure of a hose will go right up to the full pressure even if it's only cracked open a bit. Flow is reduced that way, but pressure is not.

DougM

It seems to me that the pressure in the system cannot ever exceed the 15psi that the rad cap will hold, regardless of the pressure of the hose... of course this is ASSUMING that hose was only cracked and trickling, and the flow was low enough to escape through the rad cap without the restriction increasing pressure much beyond 15psi.

 

[Slomo]

Another Question I just thought of. I still have the week old batch of Mobil 1 with only trace amounts (small drops of cloudiness most oil clean) of water in it. After I do the head gasket repair should I change it and use regular oil for a short period to flush all the debris and then go back to Mobil 1 for the regular oil? Can I safely run the Mobil 1 that is in there for a very short time? I would like to save some money but don't want to risk the engine.

 

[elmariachi]

Can I safely run the Mobil 1 that is in there for a very short time? I would like to save some money but don't want to risk the engine.

Do not run ANY oil that has the appearance of water in it.

 

[CJF]

So you're completely convinced your head gasket's blown??

Curtis

 

[Slomo]

Originally posted by elmariachi
Do not run ANY oil that has the appearance of water in it.

I thought so but was hoping against hope.

originally posted by CJF
So you're completely convinced your head gasket's blown??

Curtis

Yes, between constant air coming out in the cooling system while running and water in the oil it sure seems like it to me. The inside of the oil fill cap in the valve cover looks like chocholate milk. It was not that way a week ago. The engine has only run a short time so the contamination is minor. After I dug around the engine compartment some more I found it still has the original 1997 spark plug wires, hoses etc, I am no longer convinced that the truck was maintained as well as I originally believed. As a back up I had a friend run my VIN with the Toyota dealer and it shows no service or warranty work in its life. Which further supports my suspicion. I was almost going to do it as PM but my wife objected. At least now I can say I told you so. ;p

 

[CJF]

Good luck, and keep us posted.

Curtis

 

[elmariachi]

As a back up I had a friend run my VIN with the Toyota dealer and it shows no service or warranty work in its life. Which further supports my suspicion.

Just a point of clarification: Toyota dealers do not have access to national service repair histories in the same way that Lexus dealers do. A Lexus dealer can tell you everything that has been done to a truck regardless of where it was done. A Toyota dealer can only tell you what was done in their shop. For this reason, it helps to know exactly where a truck lived if you are chasing service history. The check you ran only means that nothing was done at that dealership.

 

[ElJefe]

As well as the fact that many things that you menthioned... i.e. the plug wires, coolant hoses, vacuum lines etc. have no defined service life or scheduled maintanance intervals. Many of those parts are considered "replace as needed" The only time that you start running into problems with the older hoses is when you break the bond with the nipple and then can't reseal them. Some of those hardened lines will live quite happily for decades without causing any problems as long as they were not touched. Even a dealer maintained truck from new, would not likely have the wires replaced unless there was a reason to believe that they were faulty i.e. a missfire or rough running, or the hoses replaced unless they were visibly cracking/deteriorating/leaking.

There is a difference between well maintained and obsessively maintained, and many here cross that line, but I doubt that many... if any... of the 10+ year old trucks out there for sale, even the 1 owner dealer maintained trucks, will have been maintained to the level of the maintainance zealots around here.

 

[Slomo]

Originally posted by elmariachi
Just a point of clarification: Toyota dealers do not have access to national service repair histories in the same way that Lexus dealers do. A Lexus dealer can tell you everything that has been done to a truck regardless of where it was done. A Toyota dealer can only tell you what was done in their shop. For this reason, it helps to know exactly where a truck lived if you are chasing service history. The check you ran only means that nothing was done at that dealership.

I assumed that they were all networked. Good to know. I will have to give my buddy some crap about that.

Originally posted by ElJefe
As well as the fact that many things that you menthioned... i.e. the plug wires, coolant hoses, vacuum lines etc. have no defined service life or scheduled maintanance intervals. Many of those parts are considered "replace as needed" The only time that you start running into problems with the older hoses is when you break the bond with the nipple and then can't reseal them. Some of those hardened lines will live quite happily for decades without causing any problems as long as they were not touched. Even a dealer maintained truck from new, would not likely have the wires replaced unless there was a reason to believe that they were faulty i.e. a missfire or rough running, or the hoses replaced unless they were visibly cracking/deteriorating/leaking.

There is a difference between well maintained and obsessively maintained, and many here cross that line, but I doubt that many... if any... of the 10+ year old trucks out there for sale, even the 1 owner dealer maintained trucks, will have been maintained to the level of the maintainance zealots around here.

I was under the impression that plug wires have an expected life and should be replaced after a certain mileage depending on the brand and quality. I guess the if it ain't broke don't fix it addage could apply. I definitely fall into the obsessive maintenance group, I just don't understand why everyone doesn't.
Good info on the hoses, I forgot about that.

Thanks all, I will post the verdict when I get the head off. Now I just need to remember to take pictures.

 

[IdahoDoug]

ElJefe,

Agree. It would just push past the rad cap. The only way someone could do that is to have some hose adapter that clamped onto the rad opening. In that case, you'd be subjecting the cooling system to the full house pressure but it would be a pretty dumb way to fill the system.

DougM