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2008 Tundra 5.7 temp issue.

Discussion in 'General Tundra Discussion' started by Primosoup, Jan 1, 2020.

  1. May 7, 2020 at 9:30 AM
    #31
    zeekevin

    zeekevin New Member

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    forgot to add i did replace the cap with a new oem cap, not loosing coolant, pass with headgasket and pressure test
     
  2. Jun 16, 2020 at 5:39 AM
    #32
    GRogdor

    GRogdor New Member

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    I've been having temp issues with my '08 5.7 and thought I'd share my path as I'm still working to fix it in case it gets some gears moving for anyone who hasn't solved their issues yet.

    The initial issue started after a thermostat replacement (stuck open and was over-cooling). Replacement was aftermarket, so I replaced it again with OEM but the problem remained. I bought a re-filler vacuum tool (OEMTOOLS 24444) and was able to get a lot of air out of the system (using the reservoir NOT the cap), but nothing changed.

    At this point, it got warm even with regular driving. Using TorquePro it would climb above 220F after 15 minutes of driving and I could watch the needle move higher as I accelerated between stops. Attempting to tow would send it straight to the red zone and I'd have to pull over and crank the heater. I noticed that the transmission temperatures were consistently higher than the engine and decided that since mine didn't have a tow package it was adding heat from the transmission. Mine is high mileage (180k) and adding an external transmission cooler and some much needed transmission maintenance solved most of the issue.

    The remaining issue... Although it's perfectly stable for regular driving and for about 30 minutes of towing, it climbs after extended towing (eg. everytime I go camping, the main reason I bought it). Seems that once it's had adequate time to warm up everything to a stable point, it never seems to cool down. I haven't driven extended without towing, since it's my primary tow vehicle for camping. Overheating is fairly slow and seems to stop shy of the red zone unless I push it hard, but also doesn't seem to recover very quickly when I give it breaks. It also becomes easier to overheat, so driving considerably gentler doesn't help much either.

    So, here are my thoughts, observations, and planned approach...

    It all comes down to air-flow and water-flow.

    Air is simple, I have a relatively new radiator with no bent fins.
    • My fan clutch is working, and my problem is most commonly seen at speeds over 40mph
    • Radiator is clear of debris and has healthy fins
    • Even during an overheat, an infrared gun shows that there's a good temperature difference top-to-bottom
    Water is always the more complex, and where I think my problem lies.
    • The heater core generated good heat, and helped lower the temp, which is usually an indication that water is flowing well
    • Pulled waterpump despite it being recently replaced. It looked new, snug bushing, no leaks, and impeller was secure and not slipping
    • Evacuated air using a vacuum re-filler in the overflow reservoir so that the cap will act as a check valve to get every bit
    • Used a rental pressure system to check that the system holds pressure and the cap pressure is good
      • Note, if either of these were an issue, I'd also expect a sudden climb in heat around 220-230 due to coolant boiling over
    • Checked for possible headgasket issues (make sure you get good block tester fluid, most places gave me bad stuff)
    • Checked the flow through the radiator to make sure it wasn't plugged up
    • The belt tensioner is good and keeping the belt tight around the waterpump
      • But more on this below
    This is usually where people end their investigation, but there's a couple more specific to this engine.
    • Related to the belt, I noticed that I could spin the waterpump by hand with the belt on and very tight!
      • My pulleys did get coolant on them during refilling, and may have during thermostat replacement as well
      • My belt was fairly new and looked good, but a closer look showed it had wide open v-grooves
      • On this engine, the belt diagram/design doesn't seem to think the water pump needs much grip
      • I cleaned pulleys and put on a new belt, I got a loud squeal for a couple minutes then went away
      • This didn't seem to be the problem for me, but might still be worth looking into
    • Lower hose - This will be my next attempt
      • After thinking about the belt being rubber and softening after heating a while, I think this is my issue
      • Despite feeling firm, it's hard to check while running (I also haven't replaced it, since it's "just a hose")
      • The 5.7 has a long lower hose and could easily collapse, but perhaps only partially
      • Replacing thermostats involve bending and working this hose, which could make a softer spot in it
    I'm a few weeks out from having time to drain coolant and put on a hose, but I'll post back here if it works for me.

    Further reasons why this gets my hopes up:
    • Once I'm running hot, it doesn't seem to cool down and heats up with lighter load
    • The heater works and helps lower the temp much faster at rest than without it and that flow doesn't rely on the lower hose
    • The overheating isn't out of control, just reduced effectiveness. The radiator is doing some cooling so it's certainly flowing a little bit
    • It's always the little things that get overlooked
     
    Wynnded likes this.
  3. Jun 16, 2020 at 8:54 AM
    #33
    zeekevin

    zeekevin New Member

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    I resealed the coolant passage under the intake manifold, replaced the t stat and fan clutch recently, before that I did the asin water pump, oem t stat, cap, upper and lower hoses, and denso radiator.

    after driving for 30 mins the temps fluctuate between 200-225°f

    I am at a loss on what to do next. The truck runs good overall with plenty of power with no other issues other than running warm
     
  4. Jun 16, 2020 at 9:15 AM
    #34
    Trident

    Trident New Member

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    shot in the dark but... heater core plugged? I've seen horrific stuff come out of them.
     
  5. Jun 16, 2020 at 11:00 AM
    #35
    zeekevin

    zeekevin New Member

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    I flush the system out 3 times already.

    what is the normal operating temp for the 5.7 motors
     
  6. Jun 16, 2020 at 11:29 AM
    #36
    snivilous

    snivilous snivspeedshop.com

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    My 2008 never gets over 204F and that's when it's working hard. Hangs around 190F the rest of the time.

    Mine started getting hot once and it was because the radiator had a crack in it and wouldn't hold pressure, but you said you replaced everything so not sure.
     
  7. Jun 16, 2020 at 1:07 PM
    #37
    zeekevin

    zeekevin New Member

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    Maybe I have a defective radiator, my temps are a solid 200-215 cruising. 220-230 when it gets warmer but it does cool back down pretty quick
     
  8. Jun 16, 2020 at 1:29 PM
    #38
    snivilous

    snivilous snivspeedshop.com

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    Sounds similar to mine. Though I knew mine had a potential crack since it had some crusty shit in a corner. One day I pulled onto the interstate towing and the temperature just started climbing and hit 230 right away so I backed off and went home. New radiator and did a thermostat to be safe, and she went back to low temps. I could even drive it without towing and it wouldn't get that hot, like 210. Sounds similar to what you're having, could also be a faulty radiator cap too. I don't know if you can pressure test the cooling system, but if that's possible I would try that if you've already replaced everything else. Food for thought either way, good luck!
     
  9. Jun 16, 2020 at 2:12 PM
    #39
    huntertn

    huntertn New Member

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    I was wondering about the cap too. The system really needs to have some positive pressure to work correctly. A bad cap or crack in the radiator will prevent the system from pressurizing.
     
  10. Jun 18, 2020 at 9:22 AM
    #40
    zeekevin

    zeekevin New Member

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    i bought a new oem cap. I’m starting to think it’s a defective denso oem replacement radiator.
     
  11. Jul 6, 2020 at 10:58 AM
    #41
    zeekevin

    zeekevin New Member

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    Well I replaced the radiator with a full aluminum koyo one and am still stuck with the same issue.

    I’m starting to lose hope
     
  12. Jul 6, 2020 at 12:03 PM
    #42
    GRogdor

    GRogdor New Member

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    Do you have one of those infrared heat measurement tools?

    I was getting ready to replace my hoses but worried I'd have the same result so after a trip while it was still trying to get into the red, I looked at the hose and measured temperatures....
    This is after sitting a bit (mine doesn't cool down quickly, even after sitting idle for a while).

    I got 216F at the upper hose, 209F mostly across the black plastic top of the radiator. But it was 163F at the metal top, gradient down to 97F at the bottom. It was around 100F up the hose to the thermostat, and about 206F on the other side of the thermostat (the metal casing). My heater works (and my pump looked great when I pulled it last year), so this looks like something at the thermostat to me. Thermostat is OEM, my third as a matter of fact (no difference with others...). I read about the weep hole check valve adding 10F if installed "up" like most cars since it doesn't get enough heat to open. Looks like throttle body and heater are closer to the water pump, so that bypass hose is the main thing heating the thermostat (until it opens and closes the flow). If I take it down again, I'll be making sure that hose is flowing properly and see if I can check clearance with the thermostat piece that lines up with that end.

    Mine doesn't sound the same issue as yours, but that temp gun may eliminate some of the good parts as targets.

    I haven't been watching the actual temps on the Torque app much anymore, but recalling how the guage mapped to the numbers I sit at 190F when warm and until it hits the issue about 30-40 minutes into towing. On short tows, or driving without towing, it's quite solid at that 190F spot (slightly left of the middle). Once it climbs, it moves very slowly and I can't seem to get below 210F or so with it regularly pushing over 230F.

    Does your heat climb to a hotter zone and stay there? Or does it back down when going back to cruising? Does it rise as fast as it goes down?

    I noticed my exhaust is incredibly hot. It's quite hot just starting with a cold engine, but also feels like it'd burn you once it's running hot. I haven't put the heat gun on that to see what it actually is, but I'm curious if mine is just not "breathing" as well and is just cranking out more heat at the engine side. I am approaching 180k miles and have no idea if I have the original cats/muffler on there so I'll be checking that out soon.
     
  13. Jul 6, 2020 at 1:08 PM
    #43
    zeekevin

    zeekevin New Member

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    I think we have very similar issues, my temps drop fairly quick if I put the truck in neutral and rev it up. My temps rise under constant load it sits at 220°f per the scan gauge.

    My normal operating temps are 200-210 right now. My system feels like it is functioning fine I’m guessing a potential air bubble causing air lock. Or a bad temperature sensor?
     
  14. Jul 6, 2020 at 2:39 PM
    #44
    GRogdor

    GRogdor New Member

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    Mine does not go down quickly when I rev it, which is why I initially thought it was a water pump issue.
    It does seem to like a specific RPM, regardless of load. Just under 3000 RPM, it will cool down to about 220F regardless of if I'm towing up a hill. If I downshift to go faster, or upshift downhill, it'll heat up more.

    I suppose mine sounds a lot like a bubble too, but I've put hundreds of miles on it and would think it would've worked it's way out by now. My overflow always fills and reclaims each trip... I'm likely hitting boiling pressure and it releases a bit, since I can feel the hose go from firm at warm to soft again once it starts filling the overflow (Tested cap, but bought a new one to be safe and it behaves the same).
     
  15. Jul 6, 2020 at 3:12 PM
    #45
    jtwags

    jtwags Concrete jungle

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    Best to pressure test the whole system if you can. I use the vacuum method that uses air compressor to draw vacuum before filling. I let it sit for 10 minutes with vacuum and if it stays pegged i open valve to fill it. Found a bad heater hose on our cheby that way, barely came down after 10 minutes but just enough to know i had a leak that wasnt dripping during operation, but also didnt run hot either. If you have compressor the vacuum fill device isnt too bad on Amazon.
     
  16. Jul 7, 2020 at 5:20 PM
    #46
    zeekevin

    zeekevin New Member

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    I’ll try parking on a bigger incline first and try burping the system again.

    if that doesn’t work I’ll drain the system and do the vacuum method.

    has anybody changed their temp sensor out with this similar issue?
     
  17. Jul 12, 2020 at 12:08 PM
    #47
    GRogdor

    GRogdor New Member

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    @jtwags I put a vacuum on it for 15 minutes and it went from 24 to about 23.5. It was morning with the sun coming up, so I'm not sure there's a leak in my case. When I pressure tested in my garage last, it held the pressure for over a half hour, and it should be under pressure while at operating temp.

    However, I dug into it this morning and I'm quite certain I found my issue (it was the thermostat bypass!). I still need to do a towing test to fully verify, but it checks off all the boxes...

    My symptom "hints" were:
    • Overheating more in colder temperatures
    • The heater worked fine (on the same hose, the transmission cooler was seeing the high temps flowing as well)
    • The radiator was cooling as water went through
    • It wasn't the waterpump or thermostat, replacement had no change
    • Once it got higher into overheating, it seemed to stop increasing
    • The biggest hint, it was cold at the thermostat but not on the back of the housing
    Tearing into it this morning, I found what looks like parts of a radiator cap in the bypass connector of the thermostat housing. It makes perfect sense now, my thermostat wasn't getting enough heat to open up.
    I never had a cap fall apart, but I'm guessing the previous owner did (and might have been why I got a good deal on this one, lol).

    One thing I don't see come up a lot in response to the "why not remove the thermostat" question is the bypass function. The thermostat actually plugs off the bypass loop as it opens, so it'll force more flow through the radiator.
    In this case, however, I think the transmission warmer competes as well, so when it's plugged (and thermostat doesn't open), all flow ends up going to the transmission warmer. Which also explains why my heat issue did improve a little when I installed a transmission cooler...

     
  18. Jul 12, 2020 at 1:30 PM
    #48
    jtwags

    jtwags Concrete jungle

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    Good find, hopefully this will get the temps to normalize for you. This is a good post for anyone else troubleshooting. I wonder if there is a way to test for this without tearing it open.
     
  19. Jul 12, 2020 at 2:27 PM
    #49
    GRogdor

    GRogdor New Member

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    It might be testable. When I was using my temperature gun, there was a 100F+ difference in temperature between the two sides of the thermostat (black plastic vs. metal housing) even after sitting a few minutes after overheating (~100F to 220F). The aluminium housing might transfer heat even if there's cool water sitting around the thermostat.

    It might be even clearer to measure further back on the housing towards the water pump inlet, but there's a chance it wont be a big difference. However, if the heater works very well, the radiator is cool at the bottom, and there's any sizable temp difference around the thermostat, then I would lean heavily towards this sort of issue.
     
    jtwags likes this.
  20. Jul 13, 2020 at 6:41 AM
    #50
    blanchard7684

    blanchard7684 New Member

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    fantastic thread. Thanks.

    So this can be not only a thermostat not getting heat, its also a flow restriction.
     
  21. Jul 13, 2020 at 9:41 AM
    #51
    zeekevin

    zeekevin New Member

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    Thank you for posting that bit of information up. I think that may be the root cause of my issue also.
     
  22. Jul 13, 2020 at 6:23 PM
    #52
    zeekevin

    zeekevin New Member

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    Well I didn’t find anything in there and bleed the system again. Back to square one.740B26E0-46AC-49FA-A22F-EAFB36A6FA01.jpgE8553349-4B79-48EA-9ADC-FB5F92B56CA2.jpg
     
  23. Jul 14, 2020 at 5:47 AM
    #53
    blanchard7684

    blanchard7684 New Member

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    Its possible that removing the housing and disassembling may show something...

    debris stuck in thermostat?
     
  24. Jul 14, 2020 at 8:24 AM
    #54
    GRogdor

    GRogdor New Member

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    @zeekevin Does your temp fluctuate even at idle? Do you overheat even without a load? Do you have to back down to keep it from climbing past 230?

    Thinking out-loud here...
    Even with my blockage, idling/cruising warmed up to a fairly solid 190F which, to me, means the thermostat had to be regulating properly. That temp didn't fluctuate at all, and rose/fell mostly according to load (albeit, very slowly). I'd point to the temp sensor if it wasn't load based and more random, but you mentioned that you can cool off quickly by revving it up, which I think means that you have good airflow but may mean water-flow may be less ideal (likely why the new radiator made sense).

    Mine was a water-flow issue obviously but, in my case, the thermostat was inevitably the culprit preventing the flow through the radiator. If your bypass is clear, and you have a good thermostat, I can't imaging the thermostat not opening. Even if heater core, throttle body, and transmission cooler was plugged, it'd just force more flow through the radiator. I saw a post in another forum talking about new radiators coming with plastic plugs and one getting jammed in the lower hose, if you haven't checked that already. I wonder if you could feel it from the outside of the hose so you wouldn't have to drain it all over again...
     
    Wynnded likes this.
  25. Jul 14, 2020 at 10:22 PM
    #55
    zeekevin

    zeekevin New Member

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    @GRogdor

    my temp rises slowly to from ambient temp to 200-205. It gets warm just driving normal. I had the engine pretty much tore down when I resealed the coolant valley and did the cam tower and timing chain cover reseal.
    during that time i did not see any FOD in the system.
     
  26. Jul 25, 2020 at 9:42 AM
    #56
    blanchard7684

    blanchard7684 New Member

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  27. Jul 25, 2020 at 9:49 PM
    #57
    zeekevin

    zeekevin New Member

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    Nothing, it sits on the side of the house or just short trips around town to pick up stuff from the store
     
  28. Aug 22, 2020 at 3:38 PM
    #58
    busterg

    busterg New Member

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    on the same boat as you @zeekevin, I have obd with torque and my temp will hang arround 205 going 75mph sometimes. I did a slow climb up a mountain 15mph with it and saw temps rise to 209 w/o towing anything and this was a slow climb, I live in Tucson AZ so it does get hot here. I ordered a oem clutch fan to replace, I will update you if that improves anything, you would think going 75mph would bring temps down. temp also hangs around 204 just in idle with ac on, thats why im just going to replace the engine clutch fan see if that improves anything. My next guess would be thermostat again from mishimoto that opens at 160f. I forgot to mention, I just replaced the radiator, thermostat, hoses, water pump and v belt.
     
  29. Aug 22, 2020 at 5:13 PM
    #59
    zeekevin

    zeekevin New Member

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    More and more people are having this issue and all signs point to airlock. Gotta find a better way to burp the cooling system
     
  30. Aug 22, 2020 at 5:45 PM
    #60
    blackdemon_tt

    blackdemon_tt Battery Slayer

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    This shit sounds like this old Corolla from the late 80's we struggled with back in the day... It would overheat at stops and would cool down when it moved... there was no real resolution, just dealt with it for the longest time. MR2s have similar issues without any known issues.
    I haven't caught whether the poster's truck is equipped with a tow package or not. Would it be possible that the transmission thermostat be a contributing factor in triggering the overheating, since it appears to be related to towing? Maybe even the transmission radiator?? I've lost the same piece of radiator cap, but I haven't seen any temperature change, and I've yet to find it as well.. Would it be more of an electrical issue or even an ECM issue?? On my 07 my fuel gauge doesn't read correctly, but sometimes it does.. Any chance the coolant hoses were swapped at the IAC?? causing air to go in the system triggering an overheat??
     

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