The Chrysler Minivan Fan Club Forums banner

Recurring radiator issue, blown head gasket?

909 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

Automotive tire Motor vehicle Camera lens Rim Automotive wheel system
See less See more
1 - 2 of 32 Posts
Can I use some silicone grease between the cap and the neck to help seal it? I don’t believe that four different caps are all faulty in a row, each one being a different brand.
That will just make a mess.
If you know that the radiator is stock or a Mopar unit it could be that you are being given the wrong radiator cap. The only way the cap would leak as you describe is if there was a great amount of volume of coolant or air leaving the radiator. I would imagine it would take a couple cylinders to make it do that and you would know there was another problem.

what gets my attention is that you say you have driven the van for some time after the initial “puke” and the level does not change. That is basically the way old cooling systems worked. You did not fill the radiator full when cold.

You said you checked the hose to the overflow tank,,,did you check the overflow tanks vent? If that is plugged that could cause your symptoms.
  • Like
Reactions: 2
Well there you have it:
View attachment 72367
I really did not think I’d find anything out of the ordinary with the reservoir, but after a good ten minutes of pulling and straining I got the overflow hose off only to see this.

I couldn’t even poke a paper clip through that gunk, it’s an absolute miracle I had coolant bursting out of the cap instead of a blown hose on the highway. Another trip to the junkyard is in order it seems.

I suspect that before the previous owner replaced the water pump, they used some stop leak to try and remedy a leak in that area, thereby causing this tough gelatinous buildup. At least I learned that lesson the easy way, to not to use stop leak in any of my vehicles.

Thank you all so, so much for the help. I genuinely would not have ever found this out on my own and it’s why I keep coming back to the forum. Much appreciated everyone.
I would remove the overflow tank and drill that plug out and not worry with the junk yard. But glad you found the problem.
  • Like
  • Helpful
Reactions: 4
1 - 2 of 32 Posts