[mercury4221]

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 gauge started to rise rapidly when going 55 mph on the highway. This was about 20 miles into the trip. Before that point, the temperature gauge 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). 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 gauge 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 occurred 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.

[richards mopar]

If I`m not mistaken a`92 van came with an electric fan at the radiator. Check the wiring for the fan. If not check the fan clutch. Make sure the temperature gauge is in proper working condition.

[TxGreaseMonkey]

It's very possible the radiator needs replacing, due to mineral build-up. Never use tap or well water--only distilled water. The link below should help:

https://www.askmehelpdesk.com/cars-t...tml#post235973

[bones55]

I have the same problem with my 1992 ram 250 van. Did you ever come up with a solution? I think the radiator is too small.

[rustyluthier]

Check Fan clutch

[Kraut]

Having wrenched most of my life, and working in a heavy truck shop I can tell you places to start. Usually if a vehicle overheats under a load, as in driving down a highway, it is almost always the radiator is bad, as in not flowing coolant through all of the tubes evenly or at all. Take a laser temp. gun and check each tubes temp as you go across them and down them. You will normally find a large discretion between one that are open and flowing and ones that are plugged, if this is the case a new core is in order. Sometimes the clutch fan can also be not working, but normally it will overheat at a lessor load. I hope this helps!