Cooling/heating system malfunction

Last Edited By Krjb Donovan
Last Updated: Mar 11, 2014 07:47 PM GMT


QUESTION: Hi, My van started overheating a few months ago, and I was told I needed to change out the Thermostat. It is a 1998 Dodge Caravan with a 3.3L Engine. I followed the instructions to change out the thermostat that were in my repair manual (Chilton? Clymer? - Not sure which one). Back in December is when I changed that out. But since then the engine started overheating again. This time, I had the coolant flushed by a local mechanic. After I got it back it STILL overheated. That mechanic told me to add coolant to the radiator. When I did, although the engine was overheated, the radiator was COLD and EMPTY. There was a small amount of steam coming out of the radiator. The hose going to the top of the radiator was HOT, and the coolant in the reservoir was filthy and bubbling. Not hot, just bubbling. Adding a gallon of 50/50 coolant to the radiator made a huge difference and the engine seemed to calm down immediately. But then this morning the whole scenario started right back up again on my way into work. I've been very puzzled by this. There does not seem to be any coolant getting into the oil or into the exhaust, but I do think it is spilling out of the overflow in the reservoir while I'm driving. Also, there are NO PUDDLES under my car where I park on a daily basis. What could possibly be wrong? Is there a blockage in the radiator? Is the Water Pump bad? Did my mechanic rip me off? He's certainly not offering to fix the problem for me. I need my car for my livelihood, and it's been spending way too much time in the shop lately, and I'm going broke over the dumb thing! (Sorry, just venting a little.)

ANSWER: It may be that the radiator is either crudded up and not allowing coolant to flow through it or that the water pump is not doing a good job. With the radiator filled and the overflow bottle also filled to the mark, start the engine and let it warm up. Listen for bubbling, and watch the gauge and for any overflow. The radiator's upper and lower hose are on the same side which meand the coolant has to flow across the radiator to the manifold on the opposite side from the hoses and then back to the hose-side where it exits from the lower radiator hose. The upper hose will be hot if the thermostat has opened, but if the radiator is not flowing freely you will find the the far-side manifold is a lot cooler than the mainfold where the hoses are located. It should be quite warm (not cool) if the flow is good going across and back. So assess that flow situation to begin this process of evaluation. Roland

---------- FOLLOW-UP ----------

QUESTION: Thanks for the info. That is what I was thinking too. However after bringing it to a mechanic who tested the van, he told me I had a bad head gasket and that the bubbles in the overflow reservoir was actually exhaust gases. The mechanic performed a "Block Compression Test"(which changed the color of the radiator fluid when carbon monoxide was present). I know the van needs a new EGR valve as well, so I am really hoping the mechanic was wrong. The repairs for a head gasket would start at $1,200.00. The EGR valve was going to be a few hundred dollars and also the rear valve cover is seeping oil and needs a new gasket. PLUS the windshield has a nice 12" crack in it from a stone chip. So all in all, the van easily needs well over $3,000.00 or more worth of repairs. At this point, It's just not worth doing.


PS With regard to the broken radiator draincock, the way to remove it is to turn it counter-clockwise until it comes to a stop, then turn it clockwise 1/8 of a turn and then pull on it. If you can get to to that position it should be removable without damage to the radiator. Then you can buy a new drain cock at a dealer or radiator shop. Good luck!

Hi George, One idea to get some further use out of it would be to try to stop the gasket leak by putting some Bar'r Leak head gasket sealer in the cooling system. If you aren't losing coolant to the oil or exhaust system in any large amounts that might just work for you. Then you would only need to do the valve cover gasket and the egr which you could you do yourself if inclinded. It may be by the way that the head bolts on one side or the other are a bit undertorqued which also can cause a slight leak. So at least when you put a new gasket on the side that leaks oil you could try backing off all 8 head bolts while you have the cover off, about a quarter of a turn, then torque them to 65 foot-pounds starting with the center (rear) under cover and going across to the opposite side, then the center (front) under the cover and across to the opposite side, etc. Then in the same pattern torque all eight bolts 1/4 turn further. You could do it on the other bank of cylinders as well. If you are lucky the leak will stop by doing this. I've been able to seal slight leaks this way with my vehicles without using Bar's leak, when the issue was really just loose bolts. But then if not successful you can try the Bar's Leak which should work. The egr may just be 'cruddy' as far as the action of the valve stem so you could try squirting some WD-40 on it where it enter the body of the valve and then work the stem back and forth by means of a screwdriver tip inserted in the circumferential slot of the stem. The internal spring-action should close the valve to a dead stop and that may solve that problem. Roland


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