Expert: Ben Deutschman - 7/21/2006

Question
Ben;
I wired to fan to stay on when the engine is running. What's the best way to flush the system? Should the engine be running or off when bleeding for air?
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Followup To

Question -
Ben;
  We have a 1990 Dodge Caravan 2,5L with Turbo and just replaced the cylinder head with a new one. It runs great,but when the A/C is on it tends to  overheat or runs hotter. we had to convert the R12 to R134. The A/C gets real cold,but is it possible for the A/C to make the engine to run hotter temp?We installed temp gauge and it reads 190 most of the time except when the A/C is on for a long period of time.Sure don't want to do another cylinder head again!!! OR could it be the Turbo WasteGate?

Answer -
While this is a little out my area, I'll give it a try.
Generally speaking, A/C won't overheat an Engine with a properly functioning 'Cooling System.' If the Thermostat were not opening fast enough, or was stuck shut, that would overheat the Engine. If the Radiator was clogged with sediment, accumulated from poor Cooling System maintenance, that would cause overheating, and even more so when the Engine is under load (such when the A/C is on). A bad Fan Relay, or Sensor, that isn't kicking the Fan on when it's needed, will also cause overheating, especially when the A/C is on. As long as you don't have a cracked Engine Block, or Cylinder head, than you can rule those items out as possible causes of your troubles.

I'm not certain if the 1990 2.5L still had a Distributor, but if it does, and it is adjustable for Timing purposes, that would be another thing to look into. If the Timing is too retarded, the Engine will labor, and when placed under additional load, overheat.

Hope this helps.

Answer
Depending on how badly gooped up the system is, an ordinary Garden Hose flushing may or may not help, but it is worth a try. If the Garden Hose method doesn't work, and your Van has a Brass Tank Radiator in it, it may be able to be 'Boiled Out', and or 'Rodded' to clean it out. The Block, if it's badly gooped up, may require professional attention, as most home fixes won't do much for it.