Overheating problem in 1992 Dodge B250 van

I have a van that still has an overheating problem though it has been to the shop. The places that did the repairs replaced one of the heater hoses and the bypass hose which fixed the initial problem of overheating and leaking coolant. The leaking has not occurred since then. However, the temperature guage started to rise rapidly when going 55 mph on the highway. This was about 20 miles into the trip. Before that point, the temperature guage was indicating that the engine was at the normal operating temperature. So, I pulled over to check out what was going on. I checked underneath for leaks and found none. When I checked the coolant overflow reservoir, the tube going to it from the neck of the radiator was too hot to touch and the water was bubbling (possibly boiling) and the level in the reservoir was about 3/4 full. Also, I could hear boiling from inside the radiator when I put my ear close to the radiator cap without burning myself. I let it cool for a while and started it back up again, when I put the engine to about 1500 RPM, the temperature reported on the guage would decrease back to operating temperature. I'm thinking that the radiator could be clogged as some radiator stop leak has been placed in it before.

The ambient temperature at which this occured was about 85 degrees Fahrenheit to 90 degrees Fahrenheit. Turning the heat on to maximum heat decreased the temperature, but it rose back up about 2-3 miles later.

The engine in this van is a fuel injected 318 cu. inch (5.2 L) V8.


Once the engine cooled enough to open the radiator cap, the coolant level was the same as that with which I started. So, I lost no coolant.

The water pump was replaced back in April of 2006.

Does anyone have any ideas as to the cause?
Would a blown head gakest be another possible culprit causing these symptoms? (I think it is unlikely since I'm not losing coolant)

Thanks in advance for any ideas that can be offered.

There is two things I would check out. The first being you're thermostat, an extremely cheap and easy job. The next would in fact be you're radiator where you had mentioned before about it having had stop leak put into it. This could cause a clog if the vehicle had sat for an extended period of time.

I believe that the thermostat was replaced by the shop. I notice that when driving it 2-3 miles that temperature increases, then decreases below operating temperature and then comes back to operating temperature, which I believe is when the thermostat opens. The thermostat is very hard to get to as it is under the belt driven accessories. Also, the vehicle has been used on and off.

How would define an extended period of time? more than one week?

I'm thinking that replacing the radiator would be a good call at this point since it is the original radiator and backflushing it could cause any weak spots in the radiator to fail. Would this be a good idea?

I'm thinking that replacing the radiator would be a good call at this point since it is the original radiator and backflushing it could cause any weak spots in the radiator to fail. Would this be a good idea?

Yes, that would be the best thing to try where that is where most of the overheating problems come from. Quite often the fins bend up or as in you're case someone has used some kind of stop leak and either let it sit for like a week and the stuff stays where it is. I would call a week an extended period of time with that stop leak in there because although most are designed only to solidify when it contacts air and coat the inside of the radiator with the rest, they typically do solidify to a certain point(enough to cause a clog). And yes in most cases backflushing the radiator will show you weak spots in it that you never knew about nor wanted to know about and you would wind up having to replace it anyways. So the replacement is the smartest way to go about it.

I drove it around today in stop and go traffic (8 miles) and it did not give me any trouble. In fact, the needle would get to the 1/3 mark on the gauge and then go down halfway and then come back up and stay at the 1/3 mark while fluctuating a small amount. I figure that is from the thermostat opening and closing. If the thermostat were the problem, I figure that the water temperature would increase lot sooner, correct?

You would think that, however it does depend. If the thermostat is stuck open, it would take forever to heat up and in the winter time, would make you're heater useless. If it were stuck closed however, it would heat up at a normal rate, but it would not stop heating up and over heat within a little while of warming up. This is just a curiosity test for you, disconnect the coolent temp. sensor's wire and ground it out, then go inside you're van and turn the ignition on. The needle should shoot to the very top of the gauge. Now, if this is the case, have someone watch it for you while you jiggle the entire length of this wire from sensor to firewall. If the needle moves from top-off, then it is a bad wire and you're van is fine. If not, the radiator change would be the next action along with running a garden hose through you're upper radiator hose while the radiator is out to remove any other debris that may have collected between the different owners.

I would think that the gauge is working as the time when it got close to overheating, I heard boiling and the gauge reflected that (it was centered between the max on the guage and the 2/3 mark). Also, if the thermostat were stuck in the closed position, would it overheat within 8 miles of stop and go traffic?

Also, it has been throug a lot of coolant changes. This may seem a bit far fetched, but could the radiator cap be a culprit here? It was replaced back in January 2006. This just occurred to me as the reservior was about 3/4 full and boiling when it came close to overheating.

Is it also possible that there could be air pockets in the system as it has been recently worked on?

well in order to get rid of air pockets you run the engine with the radioator cap off.

For how long should I run the engine without the radiator cap (while parked of course)?

not too long

you should see those bubbles come right up the radiator cap if that is the problem.

Im not positive how long it would take to make 100% sure I mean not long you have to get the entire coolant to run through the system once right?

I mean concentrate on whats going on.