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four runner head problem


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bowdog
New User

Apr 5, 2010, 10:15 AM

Post #1 of 6 (1487 views)
four runner head problem Sign In

i posted the other day about my four runner having i think head problems, now i found out when you put a thermostat in it it just overheats, and with no thermostat it runs normal and there is hot heat, thats what i dont understand i thought when no thermostat no heat? any ideas


Tom Greenleaf
Ultimate Carjunky / Moderator
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Apr 5, 2010, 3:37 PM

Post #2 of 6 (1483 views)
Re: four runner head problem Sign In

Is it consuming coolant or blowing it out?

Engines need a thermostat as the open hole is too big and only on that end of the engine. When missing the water pump is just rushing coolant at that end leaving far end to overheat not indicated on temp gauge. With thermostat the thing will be wide open as needed and still mix coolant inside engine to an even temp averting warpage from hot here and cool there as metals of an engine don't like that nor head gaskets!

You can check for head gasket issues like exhaust fumes in the coolant, white smoke out tailpipe or contamination with oil.

All this still requires a good radiator, fannage to it.

Again - water pumps are generally not capable of circulating enough inside engine while thermostat is missing. Keep in mind the pump never stops pumping so when thermostat is closed it's still there keeping engine temp uniform,

T



bowdog
New User

Apr 6, 2010, 6:25 PM

Post #3 of 6 (1474 views)
Re: four runner head problem Sign In

i dont have any coolant in oil, smoke out pipe, or pressure in radiator but when i put themostat in it overheats, could it be blocke radiator


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Apr 6, 2010, 7:31 PM

Post #4 of 6 (1469 views)
Re: four runner head problem Sign In

Yes it could. One way to test is to feel the fins on engine side using all caution of fan(s) when upper hose is warm to hot you should note the heat max where it enters radiator which is cross flow and notably cooler at lower and opposite ends as coolant travels back to return hose.

Back: This behaviour with thermostat in and out is telling of a problem. When a thermostat is opened it's not as large a passage as not thermostat at all but more than adequate for flow to cool engine. It should evenly and gradually get cooler. If you ran across a cold spot or row it could be plugged up. That reduced flow capacity allows water pump to circulate all the coolant within the engine to be uniform temp. I don't totally understand why when taking it out (which is not a fix) appears to stabilize this as that may seem cooler but inside engine water jackets and far away from water pump doesn't get flow or mixed with the rest and should be running hot but not seen by sensors as they don't place them there.

I guess with thermostat out the flow is excessive and enough to satisfy some observations but that isn't right. The worry is alloys especially vs cast iron engines really expand and contract with temps and the weak link first would be head gasket and or cracking the head!

Have you tested that thermostat really opens? Old phart test is put it in a pan of water and by the usual 195F ratings they should be pretty well open. Pluck it out and watch it close up. Do totally wash any pan with a thermostat in it and rinse it off outdoors before doing that at all as antifreeze is toxic.

Now, if head gasket has a problem it might not easily do the most common things to verify. Could also be the system either pressures up too quickly for expansion or not at all (sqeeze upper hose to feel pressure) with either condition not being right there's something wrong.

One thing is that when thermostat is out, when filled all air will rise to top and not trap air in engine as thermostat would be shut giving a false sense that it's full, heater wouldn't work and low coolant would overheat. Low level or too hot to boiling won't throw heat.

Other issues without a thermostat include the engine always will send signal to enrichen fuel mixture as it may not be sending signal for mixture for a warmed up engine. Rich mixtures would cause problems but might just run cooler also - not a solution though.

Flush radiator or whole system noting how much guck comes out as seen fit. Go easy removing hoses as they can break necks on radiator and if you go further nasty to break a neck of the heater core,

T



re-tired
Veteran / Moderator
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Apr 8, 2010, 7:03 PM

Post #5 of 6 (1459 views)
Re: four runner head problem Sign In

FANNAGE ? suggestions for: FANNAGE
The word you've entered isn't in the dictionary. Click on a spelling suggestion below or try again using the search bar above.

Your repertoire of the nearly incomprehensible English linguistic offerings continues to amaze me TOM


LIFE'S SHORT GO FISH


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Apr 8, 2010, 7:57 PM

Post #6 of 6 (1454 views)
Re: four runner head problem Sign In

It's pretty remote - admitted. Should just say ability to move air.

Like "ton" and what tonnage is required to cool a given area. Real words!

Crazy

Still crazy after all these years!

Tom







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