Overheating 2003 4runner - coolant boiling in overflow reservoir

[pendragon]

I've got a 2003 V8 4runner with 225k miles.
I've known about a slow leak in my thermostat for a while, but I have just been keeping the reservoir filled while I wait on doing the water pump, thermostat, and timing belt (cash is tight at the moment).

Today, I was driving along and the check engine and two VSC lights came on. I drove about a mile before I could stop safely. At that point, I noticed my temp indicator was redlining (happened fast). So I cut the engine and got out. The coolant reservoir cap and tube was off the reservoir. I thought I must have forgotten to reinstall it, or else it popped off from steam. I reinstalled it and it started boiling the reservoir coolant. I ended up pouring in about 4 or 5 L of water, both in the radiator and the reservoir. I made three false starts, where it would cool down, I'd refill it, and make it a half mile before it started overheating. The last time, I added more water, tried to burp the top radiator hose, and the temp stayed normal 20 miles back home. Reservoir level was ok when I got home.

At home I saw the radiator cap is damaged (see pics). The dipstick oil looks clean. The oil cap oil residue is normal. I am hoping I just missed reconnecting the reservoir cap and no real damage was done (praying I didn't ruin the head - I just replaced the head on my wife's 4runner when the coolant line ruptured on the EGR and warped the head). I plan to have the timing belt, water pump, and thermostat done asap and I am replacing the radiator cap. I'll ask them to pressure test the coolant system too. Anything else to do? Think it's safe to drive in the short term until I get the work done next week?

 

[Seymore Butts]

It took 5 liters of water? Did it look like that much coolant suddenly came out when your temp gauge spiked, or was it so low for some time?

A broken radiator cap could theoretically cause boil-over because the system loses pressure, thereby lowering the boiling point of the coolant fluid. However, a sudden temp spike from normal to redline could indicate something more sinister.

I'd start by replacing all the coolant fluid and water with proper coolant and installing a new radiator cap and that hose that came loose to see if it still overheats.

Might be a good idea to check the spark plugs to see if one is wet and peek inside each cylinder for signs of coolant infiltration through the head gasket.

 

[AuSeeker]

I think you should drive it a while as is but with a new radiator cap until you see that it doing OK and not overheating again and no damage was done when it overheated, then proceed with doing the belt, water pump, etc., be sure to keep a couple of gallons of water with you until you know it not losing any more coolant

I'm thinking this all happened because the cap failed, if you have ever taken a cap off when the engine is hot then you know why a lot of the coolant boiled out into and then out of the reservoir, 5 liters is not out of the question when this happens especially when it overheats at the end, but I think you may have lost the coolant over time until it was too low and then rapidly overheated blowing out even more coolant.

Let us know how it goes.

 

[Fern]

If the cap was bad, it might not have been letting coolant from the reservoir to the radiator. Little late but you should have been checking the radiator coolant level instead of just topping off the reservoir. Hope it's ok.

 

[Seymore Butts]

I think that 5 liters of water in the coolant will contribute to excessive heat. Also, if this wasn't distilled water, I'd want it out of the system as quickly as possible, especially with such an old radiator.

While the engine light is on, see if you can download the codes.

PS. I just looked at your photos again, and there is no pink residue anywhere. Are you running something other than Toyota Pink in the cooling system?

 

[HCWatson997]

I've got a 2003 V8 4runner with 225k miles.
I've known about a slow leak in my thermostat for a while, but I have just been keeping the reservoir filled while I wait on doing the water pump, thermostat, and timing belt (cash is tight at the moment).

Today, I was driving along and the check engine and two VSC lights came on. I drove about a mile before I could stop safely. At that point, I noticed my temp indicator was redlining (happened fast). So I cut the engine and got out. The coolant reservoir cap and tube was off the reservoir. I thought I must have forgotten to reinstall it, or else it popped off from steam. I reinstalled it and it started boiling the reservoir coolant. I ended up pouring in about 4 or 5 L of water, both in the radiator and the reservoir. I made three false starts, where it would cool down, I'd refill it, and make it a half mile before it started overheating. The last time, I added more water, tried to burp the top radiator hose, and the temp stayed normal 20 miles back home. Reservoir level was ok when I got home.

At home I saw the radiator cap is damaged (see pics). The dipstick oil looks clean. The oil cap oil residue is normal. I am hoping I just missed reconnecting the reservoir cap and no real damage was done (praying I didn't ruin the head - I just replaced the head on my wife's 4runner when the coolant line ruptured on the EGR and warped the head). I plan to have the timing belt, water pump, and thermostat done asap and I am replacing the radiator cap. I'll ask them to pressure test the coolant system too. Anything else to do? Think it's safe to drive in the short term until I get the work done next week?

You are not the only one...my 2003 V8 did the exact same thing this past summer. Bad radiator cap and started redlining, filled it up, just kept boiling and disappearing...I think all I did was replace the cap and make sure to refill the coolant. IT SCARED THE HELL OUT OF ME

 

[pendragon]

I think that 5 liters of water in the coolant will contribute to excessive heat. Also, if this wasn't distilled water, I'd want it out of the system as quickly as possible, especially with such an old radiator.

While the engine light is on, see if you can download the codes.

PS. I just looked at your photos again, and there is no pink residue anywhere. Are you running something other than Toyota Pink in the cooling system?

I was running Xerex pink asian coolant, not the Toyota brand, but I think they're basically the same.

You know, it was weird. I added most of the water to the reservoir, so it was clear. Then I added a liter straight to the radiator. I had trouble getting water into the radiator because of the broken cap parts (I fished them out at home, just couldn't see well enough while roadside). Anyway, at one point, the radiator seemed to dump into the reservoir, and the reservoir fluid turned pink. Then it all disappeared from the reservoir again (into the engine, I guess).

I added Dasani water - nothing but the best for my truck, lol (a case of it was all I had). I plan to flush it all out when I get the radiator cap.

I think all the coolant blew out of the loose reservoir cap-tube and maybe also the broken radiator cap. I must have forgotten to reattach the reservoir cap last time I filled up, unless the boiling blew it off. :frusty:

 

[pendragon]

Might be a good idea to check the spark plugs to see if one is wet and peek inside each cylinder for signs of coolant infiltration through the head gasket.

I will check the plugs.

 

[Aarp27]

Reviving this thread as I just had the exact same problem today on my 04 V8 and was looking for advice.

Currently moving from Florida to Arizona with a 6x12 trailer behind me and in the middle of nowhere on I-10 in Texas I noticed a CEL with two VSC lights on. I immediately stopped cruise control and turned off the A/C while slowing from 65 to 50 in order to limp it to an off ramp. Temp gauge was completely normal at this point. However, about 15 seconds later I got a white puff of smoke and a pop from the left side of the engine bay and the temp began screaming up.

At this point I didn't have a choice but to pull off onto the shoulder and wait an hour and a half for a tow truck to get me. While waiting, I popped the hood and discovered the upper radiator hose had popped completely off. I didn't get a chance to look at the oil as I was trying to minimize the amount of time I wasn't looking at the cars whizzing past the shoulder. I did however happen to notice that my gas cap wasn't secure which seemed off as I always get it to a click when I fill up.

It's being dropped at the nearest dealership tomorrow since they weren't open on Sundays. I'm pretty antsy to get this diagnosed and fixed since I'm going to be overdue on the trailer rental as well as paying for extra hotel nights.

Any suggestions on what the cause might be? I'm hoping it's just a simple fix like a faulty cap and not a headgasket or water pump.

 

[wcjeep]

Technically, the radiator cap pressure increases the boiling point. The pressure is not really necessary. It's nice to have the extended boiling point. Hopefully only the hose gave out.

My Cummins doesn't care about anything. Other vehicles I've had to watch the gauges. Including turning on the heater in 95deg weather to keep it happy.

All else fails remove the hood.