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Old 04-02-2007, 03:00 AM
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Join Date: Dec 2006
Posts: 21
Default 4.9 engine High rpm Overheating

When i drive the van in the city the temperature remains stable. The needle points between the R and the M on the Temperature gauge that spells out NORMAL. Sometimes it goes up to the A but rapidly cools back down to the R. The problem i am experiencing is that when i drive on the highway the temperature raise up right on the A or L mark and wont cool down for about 20 minutes after i get off the freeway. These are the things i have tried.

1. tightend the hose clamps

2. add more coolant mixture of PEAK and PRESTONE concentrated fluid. I mixed the water and coolant myself.

These parts are about 8 months old.
1. 3 Row Radiator

2.Water pump and hoses

3. Fan Clutch

I noticed that the thermostat housing has coolant dripping out but stopped leaking after i tightened down the hose clamps. This help the cooling system alot but not enough. The bolt on the thermostat housing appears to look and feel like it will break in the block if remove it. The heater core is block off and plugged up by the previous ownerbecause he said that the hoses popped and wet the entire engine compartment.The parts i mentioned above are from auto zone. What can i do to fix this problem. Thanks everyone.
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Old 04-02-2007, 03:29 AM
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Join Date: Feb 2007
Posts: 1,106
Default RE: 4.9 engine High rpm Overheating

If it has that much pressure to pop hoses you have a more major problem. I'd look for a cracked head gasket or head or block into the exhaust or cylinder head. You have a high pressure crack where the piston fires partly into the water jacket in the cooling system. Did I say into the intake earlier? - oh nuts. I'll go back and change that.
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Old 04-02-2007, 03:41 AM
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Join Date: Feb 2007
Posts: 1,106
Default RE: 4.9 engine High rpm Overheating

Then again - I rechecked and what I said was right (but more rare). Increased suction by crack to intake side of system. But it wouldn't explain the blown hoses. That is pressure - not suction and would be relegated to the exhaust side which also explains the temperature increase and overheating which accompanies it.
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Old 04-02-2007, 04:12 PM
Join Date: Mar 2007
Posts: 8
Default RE: 4.9 engine High rpm Overheating

sounds like theres no thermostat in there, and if its not there to slow the water down, the engineit
would act like your exsplainin.

good luck.
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Old 04-02-2007, 07:45 PM
Senior Member
Join Date: Feb 2007
Posts: 1,106
Default RE: 4.9 engine High rpm Overheating

Not usually.The pump wouldn't allow enough pressure to blow hoses apart and pressure is the same whether or not the thermostat is there (unless the thermostat is shot). What pressure is the radiator cap? If it's rated too high over what it calls for that could cause some trouble. I've run engines plenty of times with no thermostat and it shouldn't blow the hosesapart unless you put in a high flow pump that's higher than stock and couple it with a higher pressure cap. All that seems unlikely he'd have missed both troubles though and the pressure still shouldn't do that. It should have a reinforcement spring in the lower hose to keep it from pinching shut totally. And you should pressure test the piston cylinders to check for a bad head gasket. That's the one place the abnormal high pressure could come from. If you pressure test and leakdown test the pistons and don't find anything I'll be surprised. If it doesn't have a thermostat it wouldn't hurt to put one in - but check the motor first so you don't end up pushing the antifreeze out the tailpipe on startup.
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