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Recurring radiator issue, blown head gasket?

906 Views 31 Replies 13 Participants Last post by  stidley007

I made a prior thread a while back concerning this issue but wanted to make a new one with new insights I've found. The issue is as follows:

The coolant level in my 2007's radiator consistently stays about three inches below the filler neck. It does not decrease below this height, nor will it pull in coolant from the overflow. I have driven it as such for months to confirm this. Upon refilling the level to its proper height to the filler neck, putting on the cap, and starting the engine, coolant will begin to quickly gush out from just beneath the cap after only ten minutes, when the engine temperature reaches the first notch on the temp gauge. I have been through four different radiator caps and none have stopped this behavior.

I have verified that the hose from the neck to the overflow tank is not clogged, and used a ziptie to firmly seal it to the horizontal valve in the filler neck. I can watch it, and it does not leak from the hose. I have rented an Autozone pressure test kit and pressurized the system with the engine off at 16psi. It holds pressure just fine. The mating surface between the cap and gasket is clean, tight, and free of nicks, and the caps are not missing their gasket (see photos).

This troubles me, because I am beginning to suspect there is a greater issue here. I find it hard to believe that coolant is gushing out at the rate it is after the engine barely gets to operating temperature. Part of me wonders if there are exhaust gases somehow escaping into the cooling system, creating excess pressure beyond 16psi that would cause this behavior. But if this is a case of a bad head gasket, shouldn't the engine be burning up coolant over time? It's never run dry or fallen below the same three inches under the filler neck, and I'm not blowing white smoke out the tailpipe either.

Of course I could continue to drive it this way, as most people would. But this small annoyance has been bothering me and I'll be damned if I can't figure out the issue. I've attached a photo of the cap and cap mating surface (AFTER topping off fluid). Any and all insights are welcome. Thanks.

Fluid Gas Tableware Auto part Machine

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OK, so you fill the radiator to the rim, replace the cap.
Then you start the van and drive all day, then park the car over night for the evening.
They next morning, you open the cap and oh sugar that same 2"-3" of coolant is missing again. Same as the last time I checked it a week or two ago... no more or no less,,, just about the same.

What I purport is that your vehicle has rubber radiator hoses (it's ok, mine does too)

When you get your vehicle up to operating temperature, the coolant expands and flows over to the 'expansion tank' (at least it should. The coolant expands, building pressure within the radiator until the 13-15 psi cap allows the excess to vent past to the expansion tank and stops damage to the radiator or hoses (the weakest link)

The hoses have a nylon cording inside the rubber hoses to reinforce them. Although they do not blow up like balloons, they do expand a little bit under the pressure. So are the heater core hoses expanding (if they have not been bypassed as is sometimes common in older vehicles operated in warmer climates.

Overnight, as the engine cools, the fluid contracts, and created a suction... and if / when the system is operating normally, the expansion tank refills the radiator through suction past that spring loaded 13-15 psi radiator cap. BUT it also created suction on the whole of the system, thus slightly collapsing the two large hoses slightly.

When you open the radiator cap, that suction is broken, the hoses spring back to their normal (cool, zero pressure / zero vacuum) diameter and the fluid refills them and that is where your two inches go. No more, no less.... I imagine if you had a clear window on the cap, it would be full and air bubble free right up to where you open the cap.

NOW, what you describe as coolant gushing out of the skirt of the cap??? That is not normal and I would like to see a video of that posted here. You may also post a video online on YouTuber or Flikr somewhere and put a link for us to diagnosis if you like.
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what's this? dirt or crack?
Eagle eye... myself I didn't bother to look that hard because it was filled to where I couldn't see the lower mating surface for the pressure relief.

Nice catch Atoman
what's this? dirt or crack?
Eagle eye... myself I didn't bother to look that hard because it was filled to where I couldn't see the lower mating surface for the pressure relief.

Eagle eye... myself I didn't bother to look that hard because it was filled to where I couldn't see the lower mating surface for the pressure relief.

Nice catch Atoman
Nice catch Atoman

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The best I can zoom with what I got it does appear that the little salt drop up on the radius lip has an straight line shadow down the the white spot inside the bore. Certainly worth a discerning look under an electron microscope.
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I would remove the overflow tank and drill that plug out and not worry with the junk yard. But glad you found the problem.
Yeah, might as well remove that useless (currently useless) part anyway as you are going to have to whether you can clear the clog or needs replaced.

Dorman makes a replacement tank on Amazon p/n 603-069 for like $35

I did end up removing and drilling it out. Not sure why I opted to get a replacement at first honestly.

It was extremely difficult to get good access to the three bolts, namely the bottom one, but it can technically be done without removing anything other than the battery + tray. Took me about two hours of messing with swivel sockets and small ratchets to get a good angle.

I’m going to get the cooling system flushed out next oil change as the stuff that’s in the system right now has a bunch of dirt and other contaminants in it and I don’t want to have it clog again.
Did you really have to use a drill?
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