Amazing Radiator Trick

So… it’s the last day of my vacation – and I’m in a cute little town in the Eastern Sierra Nevada mountains of California. 4400 feet elevation, 95 degrees.

On my way out of town, I decide to head up to a national park site that’s 10,000 feet elevation. I’ve been up there before, but never when it’s been that hot. It’s a long, steep road, and I have to take most of it in 2nd gear.

So… at about 9,000 feet… I see a couple small rocks. Not going very fast… but… one of them hits the undercarriage of my car with a sickening “thud” that does not sound good AT ALL. In my mind, I hope it’s not the oil pan… and since I’m almost to the parking lot of where I’m going, don’t think any more about it.

Well… I’m there about an hour. I come back to the car… and there’s a sizable puddle of green fluid dripping from my car. “OH CRAP!” I think to myself… that rock must’ve hit something… and now I’m leaking radiator fluid. Not a good thing to be leaking when you’re 650+ miles from your home in AZ… but… at least it’s not the oil or the transmission fluid (because I checked… just to make sure. Even though the green fluid was a dead giveaway).

So, I figure… if the car is low on radiator fluid and going to leak… and it’s going to be VERY HOT all day tomorrow on my way home… PLUS… whatever radiator fluid leaks out overnight while I’m asleep… I best be heading for home during the relative coolness of the night. Thinking that any repairs that need doing I’d rather do at home… where I have reliable mechanics… as opposed to driving back down to that cute little town and looking for a one there (assuming they even have the time to see me). And… since I always carry extra water with me, can just check on the radiator throughout the night en route.

So, I get to my first gas stop. About 130 miles down the road. Sure enough… the reservoir is almost empty. Since the engine is really hot… I don’t open the radiator cap… but figure it’s still leaking.

Same thing about 50 miles later. Reservoir is low. I add more water.

Same thing in Las Vegas. I add more water.

But… interestingly… there’s a huge wreck in Vegas. Stop and go traffic for about 15 minutes. I notice the car does not overheat. In fact, the temperature gauge doesn’t budge an iota. “Interesting,” I think to myself.

So… somewhere south of Kingman AZ… there doesn’t seem to be any leaking radiator fluid anymore. And… the reservoir is RIGHT where it should be. At the “full” line.

Same thing about 100 miles down the road when I stop for gas. The fluid in the reservoir is exactly the same level as before.

Here’s the punch line…

So, I waited a few hours for the engine to cool down, then checked the radiator. The radiator, is in fact, completely full of lime green radiator fluid. To the top.

No leaks on the ground either.

The only thing I can figure, is that the engine got REALLY hot (on a hot day) going up a VERY steep grade to 10,000 feet… and also maybe the barometric pressure (4400 feet vs. 10k) somehow played a part too… and caused radiator fluid to come out the overflow tube and onto the ground while I was parked there.

I did google this. Some other people apparently have experienced similar things.

Question… should I have this checked out? And what, exactly, should I tell my mechanic to look into… without giving him an excuse to make a boat payment (as Click and Clack would no doubt joke about).

Oh yeah… and… because I get this every time. Yes… I’m aware it’s a little ol’ Suzuki with high miles and that they stopped selling them in the US market. Yes, I have thought about looking for a newer car. Just want to make sure this is okay for the time being. Thanks!

You can get this checked out and confirm everything is OK… Or you can risk destroying your engine, like you did trying to drive a car with a possible coolant leak 650 miles through the desert.

Re read that last sentence and think a bit what could have happened.

You got really, really, lucky. I suggest you never do that again.


I can totally appreciate that. And yes I did get lucky. FWIW, I did keep an eagle eye on the temp gauge throughout the whole night… never more than a minute or two. It didn’t budge. Not really that I could see.

I did figure that if the coolant was low, the radiator would suck out what it needed through the reservoir. That, of course, was an assumption.

The other thing is that this is a car with 220k miles on it. And… while not wanting to lunch the engine… I felt driving home during the night was the lesser of two evils.

Again… FWIW… I did actually stop after about 25 or 30 miles and waited two minutes. Then I checked to see how much radiator fluid had leaked out on the ground. None.

I did that again after about another 25 miles. Again… none.

Perhaps that gave me a false sense of security… but I did it to see how fast the fluid was leaking out. I figured that if it was a slow leak, I might stand a chance. Still… however… that was indeed a calculated risk.

Unless there is a leak in the cooling system, it’s easier to suck air in through the leak, then it is to suck coolant through the radiator cap.


Good to know!!!

I’ve had a lot of good luck with limping leaking water pumps home by topping off the radiator and installing the cap without tightening it @It_s_Me. Until the engine is overheating all that leaks from the loose cap is steam and without any pressure the leak slows to a trickle or even stops.

I wonder if the OP’s cooling system had some stop leak in it. Whenever I opened a cooling system to repair something I dropped in a ‘builders cube’ when topping off the coolant.

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What is a builder’s cube never heard of that?

We had a vehicle in the fleet, don’t recall the specifics but it would occasionally spew coolant for no apparent reason. My best guess is your radiator cap was spewing out the overflow rather than back into the resivour. Change the cap and make sure tube to resivour is free and clear, my first thought.


I have googled the product and can’t find it. I recall it being labelled “Pioneer Builders Blocks” and was sold by an engine parts warehouse. The stuff was installed in GM engines at the factory when I first tried it. It was sold in a block of about 50 cubes each about 1 inch square and a cube was less than $20. It was similar in appearance to the AC Delco stop leak pellets available at parts stores.

except it was just a block cut to break into cubes.


Auto makers around the world add a stop-leak product to the radiators on the assembly line

Click on Overview.

I was at the Ford Ranger assembly plant in St Paul watching the trucks come off the assembly line. And I noticed the workers adding these tablets to the radiator. I asked the person giving us the tour what they were doing. They explained that, because of all the radiators/heater cores installed in the vehicles, not every one was going to be perfect. Some leak. So, they added the stop-leak tabs to prevent this from happening. Because as they stated, “We build trucks here, we don’t repair them.”



I’ve still got some of those tablets I got at the dealer for when I changed fluid. Maybe still available but the service manual called for adding a couple tablets when draining the radiator.

I would just guess someone needs to crawl under the car or get it up on a lift and determine where exactly the rock hit. Just for peace of mind. I had a similar thunk hitting a chunk of U shaped steel 500 miles from home. I did a quick look underneath for coolant or brake damage but when I got home took a look. Took out a chunk of my plastic air dam is all.


So… (drum roll please!)… it was a cracked heater hose. Not cracked that much, mind you. But when the mechanic did a pressure test today… sure enough!

The other thing is this. Someone always invariably comments about these Suzuki’s and that, gosh, isn’t it hard to get parts for them now that they’re no longer sold here? Well… fortunately, I live in a small town of a million people (I use that phrase advisedly. LOL)… parts were in stock and no problem.

P.S. - and since it was just as much labor to replace both as it was the one damaged one… figured why not, eh? So… I’m good to go… for now. At least. LOL.
So… not real sure WHY it didn’t leak MORE on the way home… but… all’s well that ends well I suppose.

Good to hear you got it diagnosed and back on the road with a continent cooling system. Years ago I had a radiator hose burst wide open driving 70 mph on the freeway in a Ford pickup truck. Coolant was spraying everywhere. I coasted off the freeway at the next exit, turned the engine off, parked on the side of the ramp, and wondered what to do next. What do you know? I see an auto parts store immediately across the street. I walk over to it, no problem, they have the exact hose I need in stock, they let me use their screwdriver for the hose clamps, and repair completed, I was back on the freeway with nary a 15 minute delay … lol …

Nice find. Similarly, our Caravan would lose a bit of coolant between gas fills. I chased it for weeks. A pressure test didn’t find a leak, but there’d be a small puddle under the van. When Mar came home one day, I rushed out and popped the hood. As she shut it off, a stream squirted me in the forehead. (Can’t get more obvious than that.) It was a tiny pinhole in the thermostat bypass hose.

When shut off, engine heat spikes and built just enough pressure, but sealed in a minute. The tech didn’t want to exceed a safe pressure. I suspect that’s why yours was “cured”… it leaked only when really hot.

Yes, I’d check under the car. The air dam could be what you heard, or it could have bounced off something serious.