[jomomma]

I have a 2002 Dodge grand caravan, 3.3 engine. 137,000 miles. The problem started 2 years ago when top radiator hose blew off going down highway. Filled coolant system back up and put a screw type clamp on hose. From time to time the hose would be very tight and system still was pressured even from setting overnight and would have to occasionally add coolant. This finally cracked the radiator neck and I had to replace it last week. All hoses, radiator cap,thermostat are new and water pump is not leaking and jetting water through radiator just fine. I have had to continually pour coolant everyday in radiator for the past month, even now after new radiator. The system is getting so pressurized that the cap is letting the pressure overflow into the reservoir and so much is being released that it is overflowing and blowing on the highway. The drivers underside is wet with coolant and the top hose is tight, even a day and a half setting. From what I have read I have had a suspicion that the head gasket is bad and exhaust gases are entering the coolant system thus forcing the coolant out. The system has been tested cold and hot and no leaks detected. So at this point I am sure this is a terminal situation and it is definately a bad head gasket. I have to add 1/2 gallon of coolant every day just for short trips to work. Would someone please confirm that this is the problem. If not, what else. I cannot afford to continue to waste expensive coolant every day and the vehicle is not worth a $3000 repair.
Jomomma

 

[Dodgeboy77]

With the radiator cap off, does the coolant bubble like this?

If so, a blown head gasket is a good possibility.

I'm surprised you were blowing the radiator hose off. I would think the radiator pressure cap would have vented off the pressure first.

 

[gusc]

My guess is you have the wrong rad cap or the overflow reservoir is leaking.

This cap has a valve that opens when the engine is cooling down so the coolant is sucked back from the res into the rad to keep out air.

And, this valve must release excess pressure when hot to allow hot coolant to flow into the res. If the system is absolutely full of coolant the expanding coolant will automatically flow into the reservoir as it is supposed to do.

Is the reservoir full or empty after sitting overnight?

What I don't understand is why the pressure tests show nothing?

Also, if the hose from the res to the rad top leaks air it will not allow the cool coolant to be sucked back into the rad. It is a simple system but will not tolerate vacumn leaks.

 

[The_big_dill]

If so, a blown head gasket is a good possibility.

I'm surprised you were blowing the radiator hose off. I would think the radiator pressure cap would have vented off the pressure first.

Not unless his radiator cap was malfunctioning.

Have you checked the thermostat?

 

[Dodgeboy77]

<<Not unless his radiator cap was malfunctioning.
Have you checked the thermostat? >>

In the OP, it said that both of these were new.

 

[1994 Sport]

Welcome to the site. I would recommend you do a block test. You should be able to borrow the tool from AutoZone. http://www.autozone.com/loan-a-tools/block-tester

 

[gusc]

That radiator cap has a valve that works two ways.

Relieving excess coolant pressure is one primary function of the cap.

That is the reason your res level rises when the engine is hot and lowers when cool.

This is the very part of this problem that puzzles me, the cap should have relieved any excess pressure.

However, after thinking it over, the whole problem may be a leaky reservoir which may be cracked and only leaks when filled with hot coolant.

 

[soliyou]

The system may get highly pressurized also if you have an air pocket or bad thermostat (stuck closed).

Does it overheats?
also when the engine is at normal operating temp and you touch the upper radiator hose, is it hot or cold?


You can rent the tool from autozone to test for exhaust gases in coolant.

 

[gusc]

Very true, steam will form in the air pocket and greatly increase pressure plus make the temp gage show overheating if the sensor is in the air pocket. Been there.

 

[jomomma]

Took car to a reputable repair shop and was diagnosed with leaking head gaskets. There are several documented cases of head bolts expanding under pressure and head actually lifting from block. Tore top engine down and found that was true. Resurfaced heads, new top end gasket set, new water pump, thermostat, cap and radiator which was cracked. Pressure problem now solved but mechanic has replaced radiator twice due to circulation problem. Problem still exist in that after several days the heater blows from cold to hot. A look in the radiator when cold shows that it is down the equal amount in the overflow. When letting it warm up with the cap off, no jetting is seen coming out of the radiator fins. Only when the thermostat is fully open and the coolant has circulated for some length of time, a rap on the throttle produces the jetting action. Is this normal for the tiny orifices to open up only under operating temps or are the radiators a bad batch. In too deep now. Ether we fix this issue or we are gonna cut our loses and trade it in.

 

[gusc]

No circulation in the radiator until the thermo is open.

Don't fully understand about the low coolant levels; "A look in the radiator when cold shows that it is down the equal amount in the overflow."?

You may have air in the system.

When the engine is cold make sure the rad is topped off and the res level is at least mid-way between low and full.

When the engine cools, if the system is full when hot, the res level will decrease and usually increase when hot.

If the res level doesn't change after cooling down there is a leak in the rad cap or the line between the cap and res which prevents suction from the res to the rad.

All this is assuming the head work stopped that problem.

 

[jomomma]

Took van back to repair shop and mechanic spent 3 hours purging air from coolant system. Time will tell.

 

[443k3.3]

I have seen where a piece of the radiator tank or well baffle, had moved out of the radiator and parked it self behind the waterpump and caused intermittent temp issues.
If the 3 hour degaus did not help, then he might try removing the water pump to check for blockage and perhaps in the larger pipes and hoses for it.

 

[jomomma]

Repeat test of combustion gases in coolant system came back negative. I think your response of the reservoir line having a crack or something that allows the coolant to return to the radiator is a good option to pursue. Coolant flows to the reservoir hot, but does not reverse flow. Same level cold as when hot. Also every other day we take it back to shop to purge air from system. I'll pass this along and see if this cures problem.

 

[gusc]

With a cracked or loose return line, air will be sucked back into the rad as the engine cools.

Same thing happens if the rad cap leaks air as it cools.

 

[jomomma]

The head work is ok. Repeated tests show no gases in coolant system. System was pressure checked for 3 hours with res line plugged at the reservoir. No change in reading. This is what is puzzling. System was bled and air pockets removed. 2 days later the system has an air lock. Cooling fans running, radiator and both hoses cold. No pressure on top hose. Removed thermostat and ran engine and topped off radiator. No more problems so far with air lock, but need heat since it is winter. Put thermostat in a pot of boiling water, 212 Degrees, and thermostat opens as it should. Can there be a high pressure crack when hot that will allow a small amount of coolant to escape and cause air to enter as the system is cooling down? Would there be evidence of this and where would you suggest looking. I have noticed that there is an odor of coolant in the rear of vehicle. Maybe rear heater core has something going on. If so, where do I look for any leaks? My guess is access to it is to remove the interior trim panel. Also, what is the small heater valve for anyway? Even the guys at the local Chrysler place cannot explain it. Me and my mechanics are running out of options. Any help would be appreciated.

 

[jee34]

My van had a coolant leak,just in front of the rear passenger side wheel,at the quick connect couplings.

 

[jee34]

By the way,did you replace your radiator cap ?

 

[gusc]

The head work is ok. Repeated tests show no gases in coolant system. System was pressure checked for 3 hours with res line plugged at the reservoir. No change in reading. This is what is puzzling. System was bled and air pockets removed. 2 days later the system has an air lock. Cooling fans running, radiator and both hoses cold. No pressure on top hose. Removed thermostat and ran engine and topped off radiator. No more problems so far with air lock, but need heat since it is winter. Put thermostat in a pot of boiling water, 212 Degrees, and thermostat opens as it should. Can there be a high pressure crack when hot that will allow a small amount of coolant to escape and cause air to enter as the system is cooling down? Would there be evidence of this and where would you suggest looking. I have noticed that there is an odor of coolant in the rear of vehicle. Maybe rear heater core has something going on. If so, where do I look for any leaks? My guess is access to it is to remove the interior trim panel. Also, what is the small heater valve for anyway? Even the guys at the local Chrysler place cannot explain it. Me and my mechanics are running out of options. Any help would be appreciated.

The smell of coolant inside the van is a prime clue. Also feel around for wet carpet at the right rear, but the best bet is inside the rear H/AC compartment.

It could also be outside as jee says but AF odor points to the inside.

 

[jomomma]

yes..new cap as well