another cooling problem

mpower

Well-Known Member
Ok so heres the deal, on my 05 tacoma v6 4x4 I am having some small cooling issues.

Past couple of summers I haven’t had any cooling issues even after adding a prerunner bumper and big trans cooler. So now all of a sudden the past couple of months ive been having these small intermittent problems with low speed cooling mainly.

First off I monitor my temps with a dashhawk , which is hooked up to the obd port. The past couple of years my temp usually hovers around 192* with the max ive seen throttling it up mountain grades in the dead of summer at 208*. Now lately its been around 195-200* and when I am stopped at a light for awhile after getting off the fwy it starts moving up to 210* real quick . when I start moving or raise the idle 500rpm everything cools down .toyota calls for a operating temp of 185-212* and up to that point the needle on the dash stays where its supposed to . but when it starts climbing up to 220-230 the needle starts moving toward hot and I shut it down(I know its not the smartest thing to do but its only happened twice and I kind of panicked when it started to get that hot)

so I replaced the fan clutch with a brand new oem unit after that .

Went out to Lucerne last holiday weekend and started having same problem again , but at night everything was fine no problems ? so when I got back I replaced the water pump, thermostat , rad cap, hoses and flushed rad the best I could.

Now that was fine for a few days until I made a trip to ft Irwin area last fri night. And started to get the same symptoms again . but on top of that I noticed that my reservoir keeps overfilling and puking up coolant every now and then ? popped the rad cap while truck was running and noticed medium sized bubbles intermittently come up to the surface. I immediately thought head gasket.

So today I preformed a cooling system pressure test ( leaked down maybe a 1/2psi in a 15min time frame)

Also preformed a hot cylinder compression test and all those results are very good??

Tomorrow im getting a cylinder leak down tester, ir thermo gun to test rad and a vacuum fill kit to make sure I got all the air out. If that fails to yield any results I guess my last indicator of a leaking head gasket would be to use a 5gas to analyze what the air bubbles are made from.

Other that that im stumped . I really don’t think it’s the head gasket , and. its just something that I really don’t want to have to do at 80000 miles. ive talked to 4 toyota service managers today and all of them said they haven seen 1 hg failure on the new 4.0 and one service manager said there was one overheating issue that only a new rad fixed. if I get a new rad its gonna be a pwr unit and im afraid that if that’s not the problem it will only mask the problem im experiencing.

Hoping someone could have some useful info that might help

thanks , mike
 

Baja Fool

Well-Known Member
Other than the obvious questions: Is the A/C on when ambient temp is 100+ degrees...

I would change the thermostat out; one that allows some flow if it fails and replace the cap, of course with the correct pressure...13, 14 lbs or whatever. Then if that doesn't work, try driving it with running the heater full blast to see if it cools significantly. If it heats up after that, it has to be the water pump or radiator cuz that really all that's left that cools the motor.

Guess it could some deal with the ignition but pretty uncommon. Those things are pretty solid.

Good luck!
 

Prerunin554

Well-Known Member
another simple question: did you check the radiator for hot/cold spots? This is the most overlooked issue and is the easiest to diagnose
 

mpower

Well-Known Member
Other than the obvious questions: Is the A/C on when ambient temp is 100+ degrees...

Good luck!
yeah its on but i had the same setup last summer w/o any problems

another simple question: did you check the radiator for hot/cold spots? This is the most overlooked issue and is the easiest to diagnose
checked to the best of my ability and checked out ok

Does your truck come with a secondary e-fan, like for the A/C?....
no secondary fan except the spal pusher i have for my trans cooler



anyways during the leakdown i had bubbles coming out of my rad from #2 cyl so im putting another motor in this week so the old one can get built up, as long as nothing is cracked or too far out of spec. just seems to be the headgasket, im hoping its that easy anyway.

anyone in the north oc area want to rent me a nice sized cherry picker or know where to rent them ?
 

Baja Fool

Well-Known Member
Vacuum leak? Low voltage to the ECU causing a lean condition? Just throwing it out there.....
 
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