# 2003 Tundra V8 Overheating **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** overheating, tundra-4wd-truck, toyota\ **Created:** [November 10, 2024, 6:44pm UTC](https://community.cartalk.com/t/2003-tundra-v8-overheating/197970 "2024-11-10T18:44:57Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![hqgrizzard\_191863](https://avatars.discourse-cdn.com/v4/letter/h/35a633/32.png) [@hqgrizzard\_191863](https://community.cartalk.com/u/hqgrizzard_191863)\ **Post date:** [November 10, 2024, 6:44pm UTC](https://community.cartalk.com/t/2003-tundra-v8-overheating/197970/1 "2024-11-10T18:44:57Z")
Radiator blew a crack in the top. I replaced the radiator, replaced the thermostat. Put it all back together and still overheats. I removed and reinstalled the thermostat on the off chance I didn’t put the bleeder at the top. Put all back together with same result. What am I missing? ---
**Author:** ![Mustangman](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/mustangman/32/44130_2.png) [@Mustangman](https://community.cartalk.com/u/Mustangman)\ **Post date:** [November 10, 2024, 6:48pm UTC](https://community.cartalk.com/t/2003-tundra-v8-overheating/197970/2 "2024-11-10T18:48:26Z")
When does it overheat? Sitting still at idle? Low speed traffic? High speed traffic? From your post, it seems the radiator cracked because it overheated. Correct? Or did you look for leaks because it was overheating? Low speed and idle overheating could be caused by a failed fan clutch. High speed, could be a failing head gasket. ---
**Author:** ![davesmopar](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/davesmopar/32/41750_2.png) [@davesmopar](https://community.cartalk.com/u/davesmopar)\ **Post date:** [November 10, 2024, 7:03pm UTC](https://community.cartalk.com/t/2003-tundra-v8-overheating/197970/3 "2024-11-10T19:03:18Z")
+1 for Mustangman Did you bleed the system with the heater on full hot?? Do you have very hot heat at the dash vents?? ---
**Author:** ![Tester](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tester/32/15976_2.png) [@Tester](https://community.cartalk.com/u/Tester)\ **Post date:** [November 10, 2024, 7:11pm UTC](https://community.cartalk.com/t/2003-tundra-v8-overheating/197970/4 "2024-11-10T19:11:32Z")
Remove the radiator cap when the engine is cold. Start the engine, and while it idles watch coolant in the radiator. If bubbles begin to appear in the coolant it indicates a blown head gasket. [![](https://global.discourse-cdn.com/cartalk/original/3X/7/c/7cf4c623221a0e2b24204a76a765ceeeaa3b13d1.jpeg "Symptoms Of A Blown Head Gasket Radiators") ](https://www.youtube.com/watch?v=ySs9LWV7AXk) Tester ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [November 10, 2024, 9:32pm UTC](https://community.cartalk.com/t/2003-tundra-v8-overheating/197970/5 "2024-11-10T21:32:09Z")
failing head gasket. ---
**Author:** ![bcohen2010](https://avatars.discourse-cdn.com/v4/letter/b/779978/32.png) [@bcohen2010](https://community.cartalk.com/u/bcohen2010)\ **Post date:** [November 11, 2024, 4:22am UTC](https://community.cartalk.com/t/2003-tundra-v8-overheating/197970/6 "2024-11-11T04:22:03Z")
Well, if the problem is a failing head gasket, technically, the head warps, as MLS gaskets don’t crush down like composite gaskets do. The good news is that this engine uses a timing belt, so it’s much easier to take apart than a modern engine with multiple timing chains, VVT, etc. Might as well fix this truck, as a new(er) model will cost way more, and be way less reliable long-term. ---
**Author:** ![hqgrizzard\_191863](https://avatars.discourse-cdn.com/v4/letter/h/35a633/32.png) [@hqgrizzard\_191863](https://community.cartalk.com/u/hqgrizzard_191863)\ **Post date:** [November 11, 2024, 1:54pm UTC](https://community.cartalk.com/t/2003-tundra-v8-overheating/197970/7 "2024-11-11T13:54:38Z")
There was no evidence of leaks prior to it happening. Temp gauge went nuts while driving home. Steam came out from under hood. Pulled off road and found crack. After replacing radiator and thermostat, engine would idle fine for 10 minutes or so. When I try to go around block, gauge spikes again. Top radiator hose is hot as hell. Bottom hose, not so much. ---
**Author:** ![hqgrizzard\_191863](https://avatars.discourse-cdn.com/v4/letter/h/35a633/32.png) [@hqgrizzard\_191863](https://community.cartalk.com/u/hqgrizzard_191863)\ **Post date:** [November 11, 2024, 1:55pm UTC](https://community.cartalk.com/t/2003-tundra-v8-overheating/197970/8 "2024-11-11T13:55:18Z")
Luckily, this is not the issue. ---
**Author:** ![hqgrizzard\_191863](https://avatars.discourse-cdn.com/v4/letter/h/35a633/32.png) [@hqgrizzard\_191863](https://community.cartalk.com/u/hqgrizzard_191863)\ **Post date:** [November 11, 2024, 1:56pm UTC](https://community.cartalk.com/t/2003-tundra-v8-overheating/197970/9 "2024-11-11T13:56:00Z")
did run heater while bleeding. no heat at all at the vents. ---
**Author:** ![Mustangman](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/mustangman/32/44130_2.png) [@Mustangman](https://community.cartalk.com/u/Mustangman)\ **Post date:** [November 11, 2024, 2:23pm UTC](https://community.cartalk.com/t/2003-tundra-v8-overheating/197970/10 "2024-11-11T14:23:44Z")
> [@hqgrizzard\_191863](#): > > When I try to go around block, gauge spikes again I think your fan clutch has failed. The fan clutch should engage when the engine gets hot. It makes the noise from the fan much louder when it does engage. You can determine this better by comparing the cold noise with the hot by opening the hood and listening. If you have electric fans check to see if they come on when hot. ---
**Author:** ![davesmopar](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/davesmopar/32/41750_2.png) [@davesmopar](https://community.cartalk.com/u/davesmopar)\ **Post date:** [November 11, 2024, 7:15pm UTC](https://community.cartalk.com/t/2003-tundra-v8-overheating/197970/11 "2024-11-11T19:15:57Z")
> [@hqgrizzard\_191863](#): > > no heat at all at the vents. That sounds like an air pocket to me… as long as the heat was working before hand… If it is full of coolant, you can normally turn the heater on full blast and it will help cool the engine temp down a little, however with a air pocket, that doesn’t always work… What rpm are you running the engine at while trying to bleed the cooling system?? If idle, then run it up to about 1800-2000 rpms and bleed it again…