2004 Tundra 4WD keeps blowing off coolant.

Hello!

New here and like a bad neighbor I need something.

Got a 1st Gen Tundra that keeps losing coolant by way of the over flow (I assume, there are no leaks as in a drip or the like). Temp gauge remains in the normal range but it will be missing in a short time. There is evidence of heated spray dried around under the hood. I replaced the radiator cap and thermostat (OEM parts). I have run the truck with the cap off and have not seen evidence the coolant is flowing at normal operating temperature. What gives?

 

So, with the cap off the coolant isn't circulating?

 

Most likely there is leak from one of the seams of the Radiator. My guess it would be down low somewhere. The dried spray you see is probably water/coolant being flung up to the top engine area by the Fan. You may have to remove the splash shield to find the leak.

 

Just go rent pressure tester from local auto parts store and pump her on up - see what's going on.

 

I'd definitely be checking hoses for nicks. It's too easy to install one or more of the hoses backwards and end up with nicks that spray.

 

I’m thinking the cooling system is pressurizing with combustion gas, either from a failed head gasket or a cracked head. A block tester with the dye can quickly confirm or deny, or you can look for bubbles in the overflow bottle with it running, smell the coolant for a gassy / exhaust smell…

 

Not that I've seen. Back in the old days, when the caps were pretty much center, you'd see the flow coming across the opening. In the corner it doesn't seem to be the case. I can drive it a bit, stop and check, nothing. Drive it a bit, stop and check, nothing. I do notice if I am in stop and go traffic I can smell coolant but it isn't always where I can stop to look for the tell tell signs. When I can stop there is usually coolant sprayed around so as you can't see where it came from. It isn't ever still flowing and it is usually about a quart tops.

 

That seemed likely, so I've tried to see where that might be occurring... I have not removed the shield. Might try combining some of these suggestions, pressure tester, removing the shield, etc... it is definitely spray when deposited....

 

I like this idea... It only seems to be leaking at times of peak temp or stress. Periodically checking the radiator and hoses seems to be giving up what you'd expect. Top hose hot, bottom hose particularly at the connection cooler than the top hose, a pretty good difference in the two temps... Any idea what range the test pressure would/should be? Ya pump long enough something will give, lol!

 

Is the thermostat oriented the correct direction for flow and clocked correctly? How old is the water pump? Common leak points on these models are cracked radiator top caps, coolant crossover pipe, faulty radiator cap (which you replaced) and the water pump neck to block seal that gets RTV. You also have the throttle body coolant lines and the heater core lines. Sounds like it’s spraying up front, so rear part of the heater core lines is probably not it. The crossover pipe leaks into the valley and drips off the back for most, so that’s probably not it either. Cracked radiator is a strong possibility. A bad upper or lower radiator hose is also possible. Mine leaked from a bad hose clamp after a timing belt job, replaced the worn out factory ones with worm drive clamps, which is frowned upon but has lasted 50k miles. Good luck with your search!

 

Been over them repeatedly... Even considered simply changing them out because they are OEM and nearly 20 years old. To date I haven't seen any leaks of any kind. The hoses are soft, but not too soft, and certainly not brittle. Removing the hose to change the thermostat was not terribly hard. The old thermostat looked fine and didn't take much to move the plunger about.... I did not bath test it but changing it out didn't change what is happening so I figured that wasn't it.

 

To date I haven't smelled gas or exhaust in the coolant whether in the bottle or in general... No oil in the coolant or water in the oil (Recently changed....). If, when, (If I don't just take it to a shop) I try the pressure set up adding dye would be easy enough...

***Wik***

 

The thermostat is just like the original that was ORIGINAL (Caps for emphasis) with the little burping pip at 12 O'clock. The Water pump is also original. Do these water pumps have the old style "weep Holes" to let you know the pump is on it's way to failing?



While I certainly haven't taken it down like this I have noted, on occasions, coolant in small but noticeable amounts puddled where the aluminum casting meets the block at the rusty spot at 1 O'clock High beneath where the casting crosses above it. I have always taken it to be over spray from another point, but I CAN (Caps for emphasis) remember thinking it could have come from that seam, but it didn't seem likely to me as coolant is dispersed all over including on the bottom of the hood... It seemed to me that that was too covered to make such a general mess unless it was putting out quite a bit and, perhaps wrongly, that would mean it would be fairly easy to see?

 

I think it's premature to be testing for a damaged block or head unless you've had a severe overheating event. It seems you have an external leak. As mentioned earlier, the first thing you need to do is remove the belly pan. If that doesn't reveal where the leak is, the next thing I would do is remove the fan shroud -- this will require removing the fan. Then re-install the fan, and run the engine to get it good and hot. With the belly pan and shroud removed, you should have good visual access to the radiator and front of the engine.

 

Got 'cha. Yeah, already looked at the requirements for doing that. Really never has gotten very hot, certainly not severe, in towing the boat it will climb higher but usually it rides right about middle ways as it always has. Things like the transmission temp light ect... do not come on...

 

First thing to do is get it nice and hot, and then pop the cap on the overflow, and watch it carefully. If there is air bubbling in the overflow, its a blown headgasket.

If you rule that out, get someone to take a look under the hood, while your reving the engine in neutral up to 3K or so. I've had cracked radiators before that only opened up and sprayed at high RPM.

 

I have just had exactly the same issue on the POS Frontier I bought. I know it's not the same manufacturer but hear me out.

1) Could smell coolant especially sat in traffic.
2) Evidence of it spraying onto underside of hood but could never find source, assumed fan spraying it just to make looking for a leak harder.
3) Had to keep topping it off, but never any great amounts.
4)Dash gauge remained rock steady...
5)Until it didn't and the bastard dumped a gallon on the road about 50 miles from home and managed to coat everything between and including the front headlamps and the spare tire in coolant.
6) Towed it home.
7) Refilled it, burped it properly and it hasn't leaked since???

So, I came to the conclusion that the previous owner, who had replaced the WHOLE coolant system, except the header tank, hadn't burped it properly. The excess pressure caused by an expanding air bubble was enough to pressurize the system to such an extent that the radiator cap sat on top of the plastic radiator wasn't able to take the excess pressure and was blowing off. All I had been doing was replacing that which had blown off and not expelled that pesky air.
I had nightmares about burping the system as some vehicles I've done in the past need witchcraft to get all the air out but this one was easy, just park it on a slope.

Which begs the question, how easy is it to burp a 1st gen?...

 

Is your timing belt original too? That's usually changed with a timing belt.

 

If the radiator has never been removed or changed it can be partially blocked with crud between the condensor and radiator. Which will lead to these symptoms as well.

 

Ya know.... This sounds pretty spot on. How do you "Burp" a Gen 1. It's a little big to toss over a shoulder... I kid I kid.... Thanks!

 

This one is pretty clean.... Just good fortune as I don't make too many special efforts to clean it. Occasionally hit it with the low pressure spray at the car wash (From both sides).

 

Actually this is now on the "To do" list... A lot of miles on the OEM Timing belt.

 

Good chance that issue is your freeze plugs. I've got one weeping that I check a few times a year. It's crusted over and has never leaked like you're describing though.

Link below with pictures from a couple of years ago.
https://www.tundras.com/threads/wha...t-gen-tundra-today.2558/page-798#post-2003026

 

Really!.... Too easy to forget. V-8's don't usually have belts...

 

Been out of the loop for a few days due to employment.... My commute is 60 miles one way so I've been driving my Wife's car she commutes 13 miles and has been driving the Tundra....

This is really sounding like a thing that might be the matter. I have a nice uphill slope I can park on... Gonna try pulling straight in (Up slope) for starters...

 

If you’re still on the OEM belt, you’re 10 years late on the change interval. Many a 4.7 2UZ had met its demise over a stupid $140 belt change.

 

Agreed. I assume that $140 counts on DIY? Rounding up parts is not going that badly....

 

The Aisin kit with all the parts needed, water pump, timing belt, tensioner, new idler wheels etc. has hovered around that price for years. Could be more like $200 or so now like everything else.

 

https://www.rockauto.com/en/moreinfo.php?pk=3290529