After searching through the archives and several shop manuals, I think I've narrowed down the cause of my splitting hoses and high pressure in the coolant system on my 130,000 mile truck. From what I've read, it seems that small crack (or cracks) in the head or a leaky head gasket could allow a pressurized cylinder to force air into the coolant system. I've split three hoses in the past month, and also replaced the heater core. It also started idling rough for the first 15-20 seconds after startup-- but not all the time. The other thing that bothers me is that I haven't noticed much loss in power if any. Should this thing be a dog now with this type of leak, or is it just not that noticeable except for the high pressure in the coolant system?

I checked the thermostat on Saturday, and while it wasn't opening as fully as new one, it was still opening and keeping the engine at good temperature.

Barring any other probable causes for this problem, I'm going to pull the head off tomorrow night and inspect it and the head gasket. I'm making a list of things that I should do while I have it all apart, and suggestions are welcome to add to it. MInd you, I'm on a tight budget, so I'm not looking to really do any performance upgrades. Timing chain was done last summer, so that's okay. Here's my list:

-Replace all necessary gaskets (intake, exhaust, head, etc.)
-Thoroughly clean inside of intake manifold and throttle body
-Change fuel filter
-Have fuel injectors inspected and cleaned (also install new o-rings etc. for them)
-Use new head bolts? (EB said that I may or may not have to, depending on condition of the ones in there)
-Inspect head and block deck for flatness and any cracks

Also, I've read some info regarding possibly torquing the head bolts to a higher spec than stock upon re-assembly. Should I or shouldn't I?

Before spending a bunch of $$ chasing a problem, step back and analyze the situation...

Think about how the cooling system works. It uses pressure to raise the boiling point of the water, and more effective heat transfer. This has to be regulated, however, or you will blow components out. The system pressure is regulated by the radiator cap. When greater than 16?PSI is achieved, it will release excess pressure into your coolant overflow tank, to avoid blowing hoses, cores, etc.

If your headgasket or head were pushing excess pressure into the cooling system, it would vent out into the overflow, either blowing the top off of it (seen it before), or overfilling it, spilling all the coolant out of the overflow tube.

Start by pressure testing the cooling system. When 16PSI is surpassed, see if the coolant is being pushed into the overflow. If not, replace the cap.

Heck, forget the test. If your cap is more than a year old, it can't hurt to replace it anyway. <img src="/forums/images/graemlins/cheers.gif" alt="" />

Thanks DRTDEVL-- I was re-reading a lot of your posts on your recent rebuild. I ran the truck for a long time, several times on Saturday, with the cap off, and the front of the truck uphill. Bubbles kept coming out of the radiator no matter how long I ran it...

The cap is about a year old. I did buy another one the other day because it doesn't seem to be venting. I'll throw that on tomorrow. But it still doesn't seem to explain the constant bubbling coming up through the radiator. I let it sit there and run for a good half hour and it kept doing the same thing.

I would hate to get this apart and realize there is nothing wrong. <img src="/forums/images/graemlins/ignore.gif" alt="" /> Thanks for the advice. <img src="/forums/images/graemlins/cheers.gif" alt="" />

A head gasket leak can start small and grow. Mine did this over the course of about a year. A decent shop can run a quick test to detect combustion gasses in the coolant.

A free trick than can tell you a lot is to go for a ride and let the engine thoroughly warm up. Leave it idling and go open the hood. Release coolant pressure by halfway unscrewing the radiator cap. Does the engine change note in how it runs?

The engine does not have to run badly with a blown head gasket. They can run just fine. In fact, sometimes they can run better due to having the chamber(s) cleaned up.

my V6 would start to bubble into the overflow tank... i was getting worried, BUT, the engine was OFF.. and it continued to boil over into the overflow tank! Replaced the cap (with pressure release just for grins) and haven't had a problem since! I know the seal was starting to rot, and probly the spring get weak.. so it would bubble.. even with the engine off.

Definately check the cap first. Whether it's good or bad, make sure the overflow tube from the rad to the tank is not clogged. My $.02. Staceman

*Okay Ive been watching this for a day or so now...all good advice and tips so far. Part that bothers me is when Jeremy ran the truck for a half hour and continuous bubbling in the radiator. Sure sign that something is pumping air into the system and last I checked the only thing capable of overcoming the cooling systems pressure is engine compression. My original head give me plenty of warning by bubbling the radiator. Next sign was coolant coming from the overflow bottles overflow tube. It took all of about a month to finally give up the ghost. Turned out to be erroded coolant passages along the exhuast side..yup all 4. When I cracked a head back in summer of 2002. The only sign of any problem was slightly rough idle on startup. Didnt think much of it since it cleared up once the engine reached temperature. A few days later I had a hydrolock situation...took 3 keyhits to fire. So I pulled the plugs and found #3 and #4 to be extremely clean. Ended up being cracks in both those chamber between the seats.
Hope this aint discouraging, just keep an eye on things and make preparations for pulling the head off and getting it checked out.
~Darin <img src="/forums/images/graemlins/baby.gif" alt="" />

That's exactly what is bothering me. I put on a new cap this morning, and drove to work. After several hours of cooling off, I pulled the cap and it still had quite a bit of pressure underneath it, but maybe not as much as before. Unfortunately, I think some of the pressure may be allowed to relieve itself through a weak spot in the radiator, because there is yet another leak formed under the truck, coming from the radiator. <img src="/forums/images/graemlins/angry.gif" alt="" /> <img src="/forums/images/graemlins/angry.gif" alt="" />

Darin- I did pull the plugs on Saturday to look at them, and none where exceptionally clean. There was one whose insulator was a bit whiter than the others, but not enough to make me really take note of it at the time.

A lot of my hoses are swelling up like crazy--- I'm just waiting for another one to blow. <img src="/forums/images/graemlins/frown.gif" alt="" /> I may have to start tearing into it tonight or tomorrow night.

Jeremy, if you have the tools to perform a leakdown test then Id try getting the engine up to temperature then doing a leak down as quick as possible before things get a chance to cool much. A crack starts off as a being invisible to the eye, while engine is cool it stays sealed. As the engine warms up the aluminum starts to expand and the crack opens-and stays open until the engine cools enough for the aluminum to contract back down. While the engine is running, the compression of the engine is alot higher than the cooling jackets pressure and would only pull traces of coolant through on its intake cycle and never be noticed as it is burned off quickly. On the other hand compression and exhuast cycles would force air into the crack...thus into the cooling system. A compression check under normal conditions wont show a crack or soft breach in the fire-ring of the headgasket in the beginning stages...a leak down may show the ugly creatures head though.
What really surprised me is all hose failures you are having. The only time I had hose failures was when using Toyota Red coolant...seeped from every end. Is your overflow working properly? At one point my cooling system was getting so over pressurized that the coolant would be forced out of the engine, out of the radiator out of the overflow bottle and Id have a steam whistle blowing Dixie from the overflows spit tube LOL. Ahh those were the days....
~Darin <img src="/forums/images/graemlins/baby.gif" alt="" />

Darin-- thanks for the insightful reply. I've been wondering the same thing about my overflow as well. I'm fairly certain it works, because when I loosen the radiator cap slightly when it's under all that pressure, air is forced through the tube into the overflow bottle. I'm still wondering if something is not right with the brand of cap that I have. I bought a Stant 13 PSI (equivalent to 0.9 bar) cap a year ago, and it seemed to work fine. This was the one I was using up until this morning, when I put on another Stant 13 PSI cap. Think I should try a Toyota cap? I might have to just to make certain that the system is working the way it is supposed to.

I am using Havoline Dex Cool as my coolant. I flushed the system fairly well of the green (that had turned to brown) stuff in the spring of last year - which was about a year after I bought it. I wasn't happy with how the coolant was looking, so I completely flushed the system several times in late November, and put Havoline Dex Cool in there again. I had some debate in a red vs. green coolant topic about whether this stuff is right for our engines or not, and I came to the conclusion that I probably wouldn't know until things went bad over the long term or not. The point of that is that it needs to be maintained, and it wasn't done that well before I got my hands on it I'm presuming.

Back to the main topic at hand though-- troubleshooting this thing. I don't have tools to do a leakdown test-- I suppose I would have to take that into a shop to do it. I don't even have a compression test gauge. <img src="/forums/images/graemlins/baby.gif" alt="" /> By a quick search, I did find a good FAQ on leakdown tests (catered to FWD cars for the how-to) : Leak down test FAQ . <web browsing> <web browsing> Oh hey, it looks like if I have access to compressed air (which I do), I should be able to thread a fitting into the spark plug hole, turn engine to TDC for that cylinder, and turn the air on to see if any bubbles start coming up through the radiator. I guess that would work for other parts of the test, too, if someone was in a pinch without a leak down tester.