Radiator leak, MAYBE a head gasket problem

Mikerizer

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#1
Make
Dodge
Model
Grand Caravan
Year
2006
Miles
85,000
Engine
3.3L
The engine was losing coolant, with no visible leak. Had to add coolant at a rate of about a gallon per 20 mile or so trip.

I did a pressure test on the system with it cold, and coolant was leaking rapidly from the driver's side of the radiator, about 1/3 ways from the bottom. So, I replace the radiator, hoses, radiator cap. I watched it idle until it reach operating temperature. Then, I put on the radiator cap. It built pressure in a seemingly normal manner. However, a few minutes later I squeezed the upper hose, and there was zero pressure in the cooling system. I looked under the vehicle, and the new radiator was leaking in the same place.

I watched more closely with the engine idling and the radiator cap off...there was a steady stream of bubbles coming up from inside the radiator. The bubbles were at a consistent size and rate. When I held the engine at a little higher RPM and topped off the coolant, the rate of the bubbles increased.

This leads me to believe the cooling system is over pressurizing, due to engine gases getting into the cooling system via a head gasket or other problem. What do y'all think? Does this vehicle have similar problems with the upper intake plenum, like the 3.8L GM motors did in the late 80's and early 90's?
 
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#2
Mike said "and the new radiator was leaking in the same place".
I could ask a buncha more guestions, but if the radiator is leaking, it will be difficult to find any other problem.
 

billr

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#3
I'm puzzled that a new radiator developed a leak, just idling. I would think the cap would have bled off pressure fast enough to keep pressure close to normal. How about doing a block test? I think you can borrow that from your FLAPS and only have to pay for the dye consumed.
 

Mikerizer

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#4
I should have given more information. Last night I was tired, cold, and frustrated.

1-there is no sign of oil in the coolant
2-there is no sign of coolant in the engine block
3-the motor runs perfectly, and no DTC is present

I'm thinking about replacing the radiator, but before I add coolant, do a pressure test, to see if the new one holds pressure. That way, if there is a leak between a cylinder and the coolant passages, I won't fill the cylinder and crankcase with coolant. If it leaks down, I'll pull the spark plugs, and maybe be able to hear a hissing sound if it's leakage. I know that sounds a little silly, but it's a start.
 

kev2

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#5
A NEW radiator or another radiator?

A new pressure cap and blowing a NEW radiator that quickly SAME location IDK.

OK pressure test the system plugs out, see what is ejected when bumping starter motor over - a spray of coolant?

I am agreeing with billr just the what and WHYs
 
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Mikerizer

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#6
NEW radiator. I was unaware of the block tester, which changes fluid from blue to yellow in the presence of exhaust gasses in the radiator. I'm going to try that later today.
 
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#7
Just read a short sentence that requires clarification. Mike said "NEW radiator."
My first thought was that Mike meant that he had installed a NEW radiator...........but after re-reading, it seems likely that a full sentence would have said something like this "I'm thinking about replacing the radiator (with a FRESH NEW one, of course) but before I add coolant, do a pressure test, to see if the new one holds pressure.



Did you install a "brand new" radiator and verified that it is actually leaking and not just having residual fluid dripping off the vehicle after the NEW radiator was installed?


The way those Caravan radiators fail can trick diagnostics...they leak the most after you leave your house, while you are driving, and by the time you get home, the fluid level is low enough that there are "no visible leaks". If no more fluid is added, more leakage happens only when the thermostet opens and the fluid comes out out of the upper rad hose and splashes against the hole in the radiator...mostly "at speed", not at idle.....so, again "no visible leaks". Just leaks while driving.

I have replaced leaking intake manifold gaskets on several Caravans with that type of engine. They don't leak into the cylinder, they leak mostly "into the valley" and the fluid dries up there, or spills out when you go around a corner.
 
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#9
Well, It sucks to have a defective new part when replacing it is a lengthy process. At least you know how to do the job (typically seems MUCH easier on the second go-round).
The Dodge 3.3 / 3.8 engine is very robust, overheating does not (usually) cause head gaskets to fail. But radiator failure in the area you describe is frequent and repeating.
 

Mikerizer

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#10
The block test revealed NO signs of exhaust gasses in the radiator. What a relief!

I'm going to pressure test the current radiator one more time. If it's leaking, I'll replace it, and test the replacement before I put everything back together....Saturday project.