2008 Tundra 5.7 temp issue.

I have an '08 Toyota Tundra RCSB that I bought back in December of '14 out of Knoxville, TN. I live in Orlando and wanted a regular cab short bed. Radiant Red TRD 5.7. SR5. Had to go there to get what I was looking for. Flew up and drove home. 10 hours. At the time it had 115K on the clock. It currently has 174K.
Loved it from day one...Ive done all the maintenance myself..no problems until Feb 2018 when I decided to take the radiator cap off and peer into the radiator. Unbeknownst to me the cap seal broke off and I discovered that the next day when I noticed the temp inching up past the 3/4 mark. At first I thought it was the thermostat...so I replaced it. Still did it ..so I inspected the cap and sure enough there was the problem. Well....it still did it. By the way..I tow a lawn trailer with it (appx3500 lbs) .
Anyway..I decided to install a new water pump, radiator, fan clutch and coolant temp sensor. Damn thing still does it. I researched far and wide and could never come to a conclusive reason why the temp gauge would NEVER move before towing hot or cold and then the cap seal breaks off and viola...temperature swings around and once over 45 and long distance..inches up past half..sometimes almost 3/4 but always comes right down when I stop.
Ive had all the tests done blah blah blah....I love all the Toyota's Ive ever owned. I drive a 93 T100 flatbed all over the place. Gauge NEVER moves.
This has me totally stumped and I'm tired of calling and researching to the nth degree. Since then...Ive just been dealing with it. I baby this thing and drive like and old man and I wish I could figure out why this happens when the radiator cap seal brakes.
Ive noticed this same thing happen to other Tundra 5.7 owners...but there is NEVER a resolution.
Hoping someone can chime in and say..."Dude..this is what you have to do"
Thanks for any insight anyone can offer.

 

Your thread is 150 from the top without a single response. I'll give you a bump. Maybe someone will see it and know the solution.

First of all, whatever is causing this issue for you, I suspect that it is coincidental to the radiator cap seal breaking. By "when the radiator cap seal brakes", I assume you mean the rubber seal on the cap crumbled up and fell into the upper radiator tank? I can't see how the debris from the seal could have gone into the engine to obstruct any water passages because I believe there is small chance the debris could get out of the upper tank.

Look at the coolant flow schematic in Post #2 by @greghoro in this thread:
https://www.tundras.com/threads/doe...t-flow-direction-on-a-5-7.58974/#post-1547127

When the thermostat begins to open near 195 deg, coolant is allowed to flow from the radiator through the lower radiator hose into the water pump suction. Hot coolant from the engine then flows through the upper hose into the upper radiator tank as cold coolant is drawn into the engine at the water pump. Unless the debris is swimming upstream, it seems the seal particles would have stayed in the upper tank until you swapped out the radiator, because the core tubes are too small to allow anything but the smallest trash to flow to the lower tank where it could be drawn into the engine.

You replaced the radiator...that should have removed any obstruction of the core. I assume you would have looked for and seen any blockage of upper or lower radiator hoses. You replaced the thermostat...I assume you would have seen any obstruction in the thermostat housing and lower radiator hose. You replaced the water pump; again I assume you should have seen any obstruction in the water pump passages or the lower hose. So...I'm thinking the radiator cap breaking just happened to be right before you began to have trouble.

You say "Ive had all the tests done blah blah blah..." It might be worthwhile to elaborate for others on what tests have been done, e.g. presence of hydrocarbons in the coolant, etc.

 

Thanks for the response!
I know it sounds too coincidental...however the temp never moved until that seal broke off the rad cap. I actually fished it out of the top of the radiator. Ive used the query " Toyota 5.7 rad cap seal broken now truck runs hotter" and I have found other people who have had the same scenario after this occured. I know it sounds absurd...I have mechanical ability and the cooling system isnt quantum physics.
The tests I had done included a leak down test...test for any issues with head gaskets and everything else one would investigate in the event they thought there might be a coolant breach or whatever that could be associated with this situation.
Like I said...since 4/18 Ive been driving it the way it is. No one seems to know whats up...including the dealer. In all the years Ive owned various makes of cars and trucks..9 times out of 10 its either a bad water pump..thermostat...or radiator.
..This debacle is something I have never experienced before. It doesnt make sense. No coolant loss. Heat is Hot. Ac works perfect. Runs and starts without issues.

 

This is a crazy problem. Does it run hotter only when towing or whether you are pulling a trailer or not? Have you tried leaving it in park and running it at around 2500 rpm in the driveway to see if it gets hotter without going down the road?

Has it ever overheated (max on the temp gauge) since this problem has started?

Do you have a transmission temp gauge? If so is the transmission temp normal?

 

Yes...hotter when towing..although before this situation. .the temp gauge barely moved.
Doesnt get hot letting it sit and idle for an hour.
NEVER overheated.
Trans temp is always just below the middle and I had a trans flush 20K ago at the dealer.

 

Almost sounds like you have air trapped in the system. Did you use vacuum to draw in the coolant or just let the system bleed itself after installing all the new components?

 

Maybe someone will correct me, but I can't see a leak-down test being of any value in determining if a head gasket is leaking. It would have to be one heck of a head gasket leak to be evident. A leak-down test is used to identify compression problems, and even normal leak-down would occur far too rapidily to identify a head gasket leak.

Here are some tests for a leaking head gasket. Note that Test #1, "milky goo" in the oil fill cap is NOT indicative for Tundra UR engines. Consensus here is that "milky goo" can appear in normal engines and is from water vapor not being boiled out of the crankcase:

https://www.youtube.com/watch?v=5zpNjYmmiYY

 

This is what I was kinda leaning towards. But I don’t know that the 5.7 has trouble with being difficult to bleed. I thought that they were self bleeding.

 

When you replaced the cap you are sure it was the correct pressure?

 

Problem is that the "gauge" is more of an indicator. Have you tried to figure out what is the actual temperature of the coolant? Maybe a cheap infrared thing from harbor freight could help by aiming it at the radiator. Check that against the thermostat rating. Then aim it in the vicinity of the sensor. Interesting issue. I've run down rabbit hole with mine thinking it was losing coolant. It just had an air bubble. It was a huge air bubble that was displacing more than 1/2 gallon of coolant

 

This ^^^^. Good idea on the infrared temp gun. There will be some error, but definitely in the ballpark.

 

When I bled the system...I cranked up the heat and let the engine idle with the cap off until it started to heat up all the while squeezing the upper radiator hose. I guess I can try to rebleed the system. Its been almost a year since I did anything to it...I would think it would have bled out completely by now had I not got all the air (burp) out. I dont know...like I said..Ive worked on tons of cars...never had this problem I know what to do.
There is no milky whatever in the oil. I just changed the oil and it looked practically new. I change it every 4500-5000 miles with 5 20 mobil 1 synthetic.
Thanks for all the input. I appreciate it.

 

Correct pressure on cap. I brought it at the dealer.

 

Has a pressure test been performed on the system yet?

 

Yes. No problems.

 

That is a head scratcher.

Check out this thread, post #15 solved his issue.

https://www.tundras.com/threads/2008-5-7-overheating.34190/

Could be something blocking the flow, like rubber gasket material from failed cap. Maybe an engine backflush and check rad for any obstructions.

 

Ive seen that post. The broken piece of the rad cap was at the top of the radiator and I fished it out.
I think Im going to order a new Toyota thermostat and see if that helps.
Truck never overheats. Actually...the real bizarre thing is that the temp wont creep up as high when its in the 90s here in Central Florida than it does when its cooler..like in the 60s or cooler. Go figure.
What is strange as Ive mentioned numerous times...the gauge never moved until the cap broke...then it wouldnt hold pressure and was leaking coolant from the reservoir tank...and I noticed the temp at 3/4.....so I was close to home...next day put in an aftermarket thermostat from Auto Zone. Piece of crap. It seemed to run even hotter. Put the old one back in it...then investigated the cap...thats when I discovered what happened.
All the time prior to this everything perfect with the cooling system. Not once did I ever have any issues. Ever.

 

Yeah, the temp running cooler in summer sounds like thermostat issue. Even new parts dont always work right. Compare the newly installed thermostat with the oem Toyota and see if there are design differences that could affect flow. Also make sure thermostat installed with bleed hole at correct position to allow air to bleed past the tstat.

 

That thermostat only goes on one way.

 

So have you done as 7.62Tundra and JohnLakeman suggested? Instead of throwing parts at it why not determine the accuracy of the guage? That could be the problem vs everything else in the cooling system, abeit heard no mention of the fan clutch being checked.

I'd try torque pro or your favorite odb2 tool. Luck and enjoy those Toyotas. : ^ )))

 

Did that. It was running at 230 at its highest mark using an Odb2 tool.

 

So does your odb2 reading follow the gauge? I read it gets 3/4 of the way up and then drops quickly at stops, does the odb2 reading follow that trend?

Yes I highly recommend using only toyo parts for critical functions like cooling, good idea to replace an autozone part there.

I've not heard too much discussion on which way is best to orient the jiggle valve on 5.7s, some other toyo engines do better with the valve pointing down, as in about 10 degrees cooler. Not saying that is the case here though.

Luck.

 

Yes..
The odb2 followed the guage. Being that the thermostat is in a housing...it only mounts one way. You have to be able to connect the lower rad hose.

 

Ever figure this out? Having a the same issue. Had shops do everything you’ve done as well. Even pressure tests and head gasket tests

about to try new radiator hoses. That and the valley leak is the only things that haven’t been replaced. I’m central Florida as well.

 

I am having the same issues also. My water temps range from 200-230°

 

i messaged Primo directly and he said it was the Autozone thermostat. He changed it with a Denzo and his problems went away. I also have an Autozone thermostat in mine. I have a new Aisin ordered, once that’s in I’m switching mine out

 

I have an oem Toyota one.

 

Have you replaced it? Mine was OEM when all these troubles started

 

It was recently replaced along with a aisin
water pump, denso radiator, oem upper lower and lower radiator hoses, and a new aisin oem fan bracket bearing. In the last 2k miles

 

Are you losing coolant? Head gasket test? Pressure test?