94 MPV overheating when driving up hill

[kjitpatima]

Does anybody know what could cause the 94 MPV 3.0L engine to overheat when driving up hill on the hot day(85 degree F)? Confusingly, it happened when driving on the high speed on freeway, but on a local street it seem to be fine. The gas mileage is poor, approximately 14 mpg combine local/highway, which before was 18 mpg combine for the same drive.

I checked the engine head with dye solution, the color didn't change.

Just replace the fan clutch, water pump, oxygen sensor, still having the problem.

Questions:

1. Could MAF cause this problem? Anyway that we can test and clean this unit?
2. Could it be the transmission? I am thinking to install a transmission oil cooler. Will it help?
3. How about MAP, water temp and air temp sensors could it cause the engine to overheat?

Thank you in advance for all the help.
kj

[gruss]

If it was the MAF it probably wouldnt run well enough to get ut of your driveway...so I dont think it was that
Unless the tranny isnt shifting inot od or something I dont know how it would affect the engine temp just on the highway
I would probably try a new t-stat if you didnt do that, maybe its opening way to late..I imagine you flushed the coolant when you did the waterpump so...
maybe check the plugs and wires too..any cel's?
how does it run normally? would a clogged up cat cause this? just throwing out ideas

[bryanj]

I'd make sure the radiator is not blocked up with crap. If its not, my diagnosis would be a $15 thermostat.

[kjitpatima]

Thanks, gruss and bryanj. I will try new thermostat. The radiator is new, but it is not the stock. Do you think that might be the problem?

Thanks again,
kj

[gruss]

If its to small fo rthe application that definately could be the problem. I wouldnt think you would need a huge radiator in an mpv but...double check the stats and make sure they didnt give you a miata radiator or something