My 1987 dodge Ram van b250 overheats. It started 2 days ago when we went up a very steep slope for 10kms. The coolant saw a hot temp while we reached the top (2/3 through the gauge scale while it usually runs a little below quarter of the gauge). I believe I also heard the coolant boil while in the van. From then the coolant is running higher in temperature, let say fairly above the quarter mark at least and can rise up to the half mark when going up a slope or when outside temperature is getting hotter. The strangest is that it is not overheating when we are idling in traffic jam, it is then just above the quarter mark, i.e my new low reference...I suspect the thermostat took a hit when it first overheated while driving up the steep slope but I am not sure.

 

You issue is with the radiator not being able to dissipate heat fast enough during the higher temperatures generated during heavy engine loads.

 

Thanks Alloro. I went to the garage today and cleaned up the radiator which was very dirty. After that the engine is still running a bit higher in temperature than usial in slow traffic. Tomorrow we will travel 500km and check what's going on during engine load.

 

install a nascar (3 row) rad

 

I fixed my hot issue when I had to replace a freeze plug, there was so much gunk in the engine block I removed all the plugs and sprayed with a water house for about 10 minutes. Before that the radiator had been cleaned at least once a year. I finally fixed my issue; the freeze plugs are pretty easy to change if you feel comfortable about the job. Just knock them out, say the internal block, from t-state and any where else you can get into.

Good luck, I thought for years I had a head gasket issue but my test always showed negative but every couple months I would check.