Recurring radiator issue, blown head gasket?

868 Views 31 Replies 13 Participants Last post by stidley007, 2 d ago

GS21

Discussion Starter · 10 d ago

2

Hi,

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.

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itsallgood

· #2 · 10 d ago

My first thought is the water pump. The plastic impellers have been known to wear down or break off in the system. Also, have you verified that the thermostat is functioning properly?

Do you have white smoke coming out the tail pipe? This is one indication of a possible head gasket leak. Check the oil dipstick for a brown milky substance on the dipstick. Do you see any oil in the radiator coolant?

GS21

Discussion Starter · #3 · 10 d ago

I’m not sure how to test the thermostat without removing it, but my oil’s been clean and no white smoke.

With the engine cold, cap removed, and not all of the added coolant puked out yet, I can watch the coolant rise up to the very top of the neck in about three minutes. This doesn’t seem normal, especially given the fluid is still cool to the touch.

itsallgood

· #4 · 10 d ago

It sounds to me like coolant isn't flowing through your system. To test the thermostat the engine has to be cold. Start the engine and let idle. Remove the radiator cap and watch the coolant get sucked down in the radiator, while coolant is coming out of the radiator cooling tubes. In your case, I'd remove some coolant from the radiator first.

The cooling fans should turn on and thermostat open, when the temp gauge is at the mark just below the halfway mark, on the temp. gauge. (That's around 220F)

Hope this makes since.

atoman

· #5 · 10 d ago

GS21 said:
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.

Are you certain the rad cap is in the "second" notch position, not first?

If pressure gets too high in cooling system, it should dump out to overflow res...

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GS21

Discussion Starter · #6 · 10 d ago

atoman said:
Are you certain the rad cap is in the "second" notch position, not first?

If pressure gets too high in cooling system, it should dump out to overflow res...

Yes, I’m sure it’s on properly in its “second position” so to say. The fact it pukes out with such ferocity from beneath the cap instead of steadily going to the overflow is what’s leading me to suspect something more foul.

atoman

· #7 · 10 d ago

Aftermarket radiator?

Even if you had and exhaust leak into cooling system and it over pressurized, normally it would be 'puking' coolant into overflow res until res is full and then overflow on the ground...

I'd personally find that OE cap and if you can carefully compare the present rad filler neck to the OE one - that second (larger diameter seal) in the cap should seal tight enough to force overflow into reservoir and yours does not...

Or you could assume the worst and do a leak down test on the (warm) engine.

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Valhallalla

· #8 · 10 d ago

I agree with atoman here. You should not be leaking coolant around the pressure cap. Your cooling system is supposed to vent any pressure over the rating of the cap to the reservoir/overflow bottle. If it is blowing coolant out around the pressure cap then you have a poor seal between the cap and the radiator filler neck or perhaps a crack in the radiator in that area that you can't see well.

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GS21

Discussion Starter · #9 · 9 d ago

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.

FabricGATOR

· #10 · 9 d ago

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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2019GTlife

· #11 · 9 d ago

GS21 said:
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.

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atoman

· #12 · 9 d ago

what's this? dirt or crack?

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FabricGATOR

· #13 · 9 d ago

atoman said:
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

FabricGATOR

· #14 · 9 d ago

atoman said:
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.

FabricGATOR said:
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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GS21

Discussion Starter · #15 · 8 d ago

I will upload a video and check that neck area and vent on Monday, I’ll be out of town until then. Thanks for all the insight thus far.

Road Ripper

· #16 · 8 d ago

Why is there NO HOLE inside that radiator neck, for the excess coolant to go to the hose/reservoir? At least that's what it looks like, a defectively made radiator. If there is no hole to allow coolant to go into the hose ziptied onto the barb, that is why the coolant is blowing out from under the cap - - it has nowhere to go!

GS21

Discussion Starter · #17 · 8 d ago

Road Ripper said:
Why is there NO HOLE inside that radiator neck, for the excess coolant to go to the hose/reservoir? At least that's what it looks like, a defectively made radiator.

The hole is present, it’s just hard to see in the photo. I’m not sure if the radiator is original or not, the only maintenance history I have on the cooling system is the water pump was replaced at some point around 2017/2018 (previous owner, not sure why or what material impellers).

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Mbriggs

· #18 · 8 d ago

You might also want to check to see of the outlet on the overflow reservoir is clogged. At one point, I used Bar's stop leak in mine and was having similar issues as you. Found that the Bar's had sealed the outlet on the overflow.

Road Ripper

· #19 · 7 d ago

The overflow reservoir would burst if the outlet was clogged, as it is thin plastic. It would at least swell up. Remember the cooling system would be at 16 psi venting off hot coolant, and if it is coming out from under the cap it might take even higher pressure than that. I wonder if the barb or overflow hose has an obstruction somewhere?

Ditto about the water pump. With the cap off and engine running, does the coolant get sucked lower in the radiator when you rev the engine by hand at the throttle body? If it doesn't, I'd investigate the water flow and possible water pump failure. Plastic impellers crack and then don't turn, while the shaft spins inside of it on some pumps. Better to get one with an aluminum impeller.

Mbriggs

· #20 · 7 d ago

The outlet for the overflow is also the inlet(2 way flow where the thin hose is attached), if it is clogged, no pressure can get in. Believe me when I say that mine was more than 16 psi clogged.😮

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