I changed the timing belt after 200k miles (3rd belt) and I have forgotten to fasten one cooling hose properly

What happened, the hose from the thermostat to the radiator popped off and I lost 2.5 gallons of fluid (from total 3.2 gallon total) and the engine overheated dramatically... I did not realize this cruising on the highway.
I heard unusual mechanical engine noises and then I saw the temperature gauge in the red zone,. also the CEL was on.
I stopped and shut the engine off. I was very uncertain if I already damaged something.



After shut engine down I saw that the one coolant hose came off and I lost most of the fluid.
On the highway I did not get the typical smoke/vapor as a sign for overheating... only when I slowed down the car.
Also I did not get a low fluid lever dash light. I saw after the fact that the check engine light came on and also

I waited for the engine to cool down and meanwhile I got some water... I connected the hose back to the thermostat housing and filled 2 1/2gallons of water (what I lost) back to the cooling system. In the beginning there was still a lot of vapor coming out.

The car started normally and I could drive home. The engine seemed to work normally. (As i had no tools to connect the hose properly I left the cap open, so no pressure could build up)

The engine ran about 100miles meanwhile and I cannot see any difference or strange behavior. Am I just lucky and nothing bad happened....or it there some aftermath with this incidence?
Questions:

-Might the engine have some damage after severe overheating?

-What can be the consequence in that event of severe overheating.


After the incident I am questioning.
Why did I not get a proper warning for low coolant level or serious overheating?
Does Toyota not have these basic warning lights.

As I said I did get the high temperature reading but no acoustical or warning signal or low fluid level.

Best, Martin

I would do an oil change and see if any metal of any kind comes out and I would carefully cut open the filter and check the filter pleats for metal. If you see no signs of metal then you need to keep close watch on oil consumption.

You may not have scuffed pistons to cylinder wall but may have scuffed the ring faces to cylinder wall. Either situation will show up as excessive oil consumption and it could start a little while from now, so keep watch if and make sure you don't run low on oil.

If you do see metal, then you know the engine is damaged. Obviously, it is still drive able, but there is damage and depending on how much to a piston(s), one could come apart and cause catastrophic failure.

If you have access to a borescope, you could pull the plugs and inspect each cylinder that way for scuffing. You would see verticle smear marks on the cylinder walls.

Our gauges are very slow to respond. Same happened to me in 2017 but no damage.

Thanks, I just did the oil change before the overheating happened (I did the new timing belt and oil change).
I'll watch and monitor closely the oil consumption from here on.

By the way... Does anyone know if the T4R 2003 4..7 has a low oil warning light
or a low coolant light?

If it cooled off and fired up and has ran for the past 100 miles the likely hood of some major damage is not high. Only thing I could think of is a possibly warped head which could cause exhaust gas in the coolant system. You'll know it's happening if you start seeing pressure built up in the coolant system causing it to push excess fluid out through your overflow tank.

With that said though.. it could be perfectly fine, or it could have resulted in some pre-mature wear, it's hard to tell without an inspection. My suggestion... if your oil looks like and isn't milky (I don't see you ending up with metal shaving in your oil from an overheat.. if it was to that point you would likely see a seized engine by now) and you're not pushing excess fluid from your overflow tank just forget it happened and be more cautious next time. But I can definitely see how missing the fact that the one gauge on your cluster that typically doesnt move once hot creeped into the red without you noticing.. I don't know of any low coolant level sensors that I"ve ever seen on this (or other cars ive had) but yea it would be nice to have an audible alarm once you peg the red zone on the temp gauge.

When you first turn the ignition on before you turn it to start, all the lights you have in the instrument cluster will light up, look and see what there, I know there isn't a "Low Coolant" light, but I would think there is a "Low Oil level" light but I don't know for sure without looking.

Also look in your owner's manual, it shows all the lights in the instrument cluster, and gauges etc.

Low oil pressure most common, oil level, not so.

Thanks everyone for their comments and answers.

I'll keep monitoring the engine oil level and the coolant level.
I have not seen any sign of coolant level nor engine oil level dropping.
Also I checked the engine oil today. From what I can tell the color is the same as the new oil I put in.
I'll keep fingers crossed but I am still cautious.

One question about the coolant type.

After I lost all of the red coolant the only coolant I could get quickly was the Presone (label claims: for all vehicles). I know that different manufacturers have their own coolant although I don't know or understand the background (for me the engines are not very different from materials....)
What are your thoughts... Can I drive with the yellow Prestone or would you recommend to change back to the Toyota coolant?

Thanks, Martin

I'll check on my dash what lights there are. However I think I have not seen oil pressure, low oil level or low coolant level.*

*I am mostly driving my old Mercedes Benz cars from the 70s to early 90s. They all have oil pressure, low oil level and low coolant level.

I would most definitely change the coolant for one that is rated for Asian vehicles, especially Japan made vehicles, the other coolants have additives that can cause corrosion in Toyota systems, it doesn't have to be the Toyota brand as long as it rated for Asian/Japan vehicles.

Thanks, that is what I will do: Change the coolant to the Toyota stuff (red or pink)

In order to drain entirely are there block drains for the left and right side block?

I have a 2004 v8 with 190,000 on it. I had similar situation with overheating except I was on the phone taking driving 80 mph when I noticed some stream coming out. By that time then looked down and noticed check engine light came on and then could hear ticking going on, then the engine then died and I coasted to side of the road. Had it towed to a shop close by and we put coolant in and it wouldn’t start. They did coolant test I think enzyme or something and it was fine. Then compression test and cylinder 3,4,7 and 8 all failed. They said engine is shot and I need a new one and quoted my around $10k. Do I need to do any more tests from another mechanic or is it safe to assume the heads are completely shot cracked or block cracked? There is no oil or coolant leaking anywhere on the vehicle. It fires up but of course dies with that many misfires. They gave me options to rebuild it at just under $10k and a new rebuilt engine at $11k with warranty. Any ideas, I’m at a lose what to do and I’m not dumping $10-11k into an engine?

on the phone talking, didn't notice engine overheating. horrible timing.

How mechanically skilled are you and how much time do you have? Have vehicle towed to your place and start your own investigation until you are satisfied one way or other that engine is junk or not. Then decide what you are going to do. If it's junk you are going to spend some bucks, or walk away.

I’m mechanically inclined and have done done extensive stuff to this 4runner and my daughters that is the same year just the v6. I just don’t know what other tests to do or take it to another local mechanic? The mechanics it’s at now seem like they are price gouging and not wanting to see if it can be done without full engine replacement. Plus the car is 45 miles from me and they know that.


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Assume the worst, that you need an engine and do your own research on a replacement; used, rebuilt, and see what you come up with. Determine what you are willing to spend to put your 4Runner back on the road and if it makes sense to have it towed home or someplace else.