Engine got a bit hot. Now Coolant on top of radiator

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J

jeanbono

Joined
May 16, 2025
Threads
7
Messages
86
Location
Australia
Hi all,

80 seriee 1FZFE - 300,000 km - located in Aus. 2 weeks ago my radiator fan got stuck in the shroud and stopped functioning when I was in traffic. Thanksfully I have caught the problem early (ish) as I saw the temp gauge get to 3/4 of the red mark. I know when it starts moving the engine is already too hot but Im still glad I did not wait till it hit the red. I’ve managed to release the fan and drive home. It had lost a fair bit of coolant which I assumed went through the rad cap (changed since then) or just forced out of the system when the engine overheated. I’ve then refilled it but today noticed I’ve got some coolant sitting on top of radiator, which was also the case right after the incident (but I assumed it had leaked from rad cap or hose with pressure). This only happened again today after a 100km drive, so it looks like it only happens when the pressure is high enough. no hose are leaking etc.

Do you also think my radiator would most likely need replacement as it seems a crack developed when it got hot 2 weeks ago? The coolant seems to come from right underneath in between the 2 metal sheet as per the picture and it does not seem to be running from anywhere else.

Re headgasket as obviously after overheating I was a bit concerned, no coolant in oil or the other way, top radiator hose still soft enough after cold start up (no combustion gas in coolant), no white smoke at start up. I think my head gasket survived…have not done a compression test yet but engine runs great, no blow bys or anything. Have not checked bubbling in coolant yet but i just dont think a 1FZFE HG could go after just one not so important heat spike (engine wasn’t smoking when it happened and I was able to drive 10K without gauge going up again after releasing the fan.

If radiator is the answer what are the best ones for the 1FZFE engine here in Aus?

Thanks for your help!

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So on the picture showing coolant it’s the right corner of the radiator next to the battery - opposite the radiator cap and opposite the overflow tank.
 
Also looks like the coolant may be flowing then pooling in that location, meaning the source of the coolant may be somewhere else. Can you take more photos and help us follow the trail?

How does the rad. cap look? Can you remove it, clean it and confirm the seals are intact and the return flow circuit is clear (under the small metal flapper valve in center of bottom)? Is the overflow tube/plumbing flowing?

I'd guess you may have a crack in the upper rad reservoir but you want to rule out the cap and the overflow plumbing first before diving into rad replacement.
 
Thanks for the reply. I really tried tracking the leak from upper radiator hose (5cm away from pooling area) or radiator cap (completely the other way) but could not find other wet areas. Could have evaporated as this problem seems to only happen under high enough pressure, I’ll take more pictures of the top of radiator later today.

Strangely when I checked the radiator after the 150km drive I was expecting to have lost way more coolant but rad was still filled to the top and nice and green.

The rad cap is one week new, I’ve ordered an OEM rad as this is aftermarket but it seems to be working ok. Only thing I was wondering is what is that blue stuff on the spring? dried coolant that turned blue?

Overflow tank hose works as i see coolant being pulled in and out.

Is there a way to tell if it’s radiator at 100%?

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That cap looks different from oem. It looks like it may work fine but I wanted to note the difference. It's important that it seals and flows correctly of course. The grease may be from assembly/construction.

It's pretty easy for a small leak to be dry by the time you stop to look at it. There's a good bit of heat on the surfaces accelerating evaporation so you may only see a faint residue line where the coolant flowed before it dried up. If the coolant is coming from the rad cap then one problem with it will be the largest seal, under the surface of the caps formed metal top. That seal should never have coolant pass by/through it. The other two seals are one-way valves, the larger one letting coolant out (and to the overflow) at a certain pressure and the smaller metal one letting coolant flow back in when the engine cools and sucks coolant back from the overflow bottle. Maybe the top seal is struggling because of the rough surface it's mating to on the radiator fill neck?

If the rad cap is new it's highly suspect in my book just because you always need to inspect any recent changes when a new problem comes up. I'd install an OE radiator cap. I'd also consider cleaning up the fill neck sealing surface if it looks like it needs it in person. A block with 400 grit sandpaper, used sparingly, may smooth things up a bit and then you can polish it a little from there if you want with a few passes with higher grits.

This is what the OE rad cap typically looks like with the main difference I see being the center one-way valve is metal on the OE and rubber on yours. Dimensions could be off in ways that compromise sealing though so it's worth checking.

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Thanks for explaining that, the OEM cap is on the way.

I however dont think its leaking from the cap, I went down and took proper pictures now to show better angles. In my cruiser the cap is the opposite direction to the left and the leak is right corner next to battery and upper radiator hose. I observed the following:

-First of all, if coolant was dripping around cap area it would not be able to flow to the other side and pool in that corner as gravity would pull it the other way (radiator has a slight curve in the middle making it impossible for fluid to climb up the middle part).
-no sign of dried coolant anywhere else than around that corner alongside the top gutter of radiator
-my first thought was upper radiator hose but it does not seem like it’s dripping from it at all and the clamp seems fine.
-I’ve however found a hose right next to it that seems to have to sign of dried leakage - not sure what that hose is? but no sign of dried coolant underneath that would have been burnt off by evaporation falling on a hot surface. Also top of radiator (the “gutter”) has a dent underneath it not sure how that happened.
-The radiator paint is peeling but there’s an area where I think I can also see dried coolant as per picture. It’s right under the top gutter, maybe it just fell from that area where it sits.

Im wondering if there would be a crack in the top tank of radiator. As this only happened after the overheating incident and was always fine before then. When I opened the bonnet after the overheating incident the coolant was exactly in that spot (hence why Im thinking it cracked then, under pressure). It only showed sign again after driving the 100 ks yesterday, not during short drives (prob not enough pressure build up)

Thanks for the help

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Last photo above looks like it could be your leak, between the brass nipple and the hose seems likely. Hose clamp looks like it may have been moved at some point so maybe the hose was removed and reinstalled which wouldn't have helped?

Pressure testing does seem like a great idea. If the rad cap is working pressure never should exceed the limit set by the cap, which lets coolant out above a certain pressure so you shouldn't have had a pressure spike related to high heat if the rad cap was working.

Good work with the photos and investigative work. I agree that it doesn't look like you have leaks at the larger hose or cap from what I see.
 
I have a very similar issue. I keep seeing trace amounts of coolant between the "fingers" on both ends, and nothing in between. My radiator is a factory unit with ~25kmi on in, and both hoses and clamps have <5kmi. No overheating. I can drive it for a good while between coolant reappearing. This is more of a seep than a leak.

I was about to order a test kit, but then it occurred to me: what would I learn by pressure testing? I already know it's leaking coolant. Is the leak tester supposed to activate the leak, in addition to the gauge showing loss of pressure?
 
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Thanks all for the reply I’ll pressure test the system
Yes I would imagine if the pressure does not hold during the test it should be able to reveal where our leaks are coming from - even though it takes a lot ot driving before I can see anything. Will keep everyone posted as I need to get the kit
 
Ok we may have a bigger issue. I had done all the head gasket tests except one, turning on cold engine with radiator cap off. result: the level in the rad rose quickly and overflowed in 20 seconds so had to turn the truck off. Not sure if it really bubbles or if’s just the shake of the liquid with the engine running. I’ll attach a video in next post. What is interesting is that I had already done that test about a year ago and it did the same…I’ve driven 20,000km since then. Could I have been driving the car that long with a failed head gasket? Looks like combustion in the coolant sort of failure or could it be something else?

Other tests:
-No white smoke at start up
-No misfiring
-No coolant on dipstick or oil in coolant
-After running the engine hot, no bubbling in the overflow tank (I’ll double check that one soon)
-Top radiator hose gets harder after start up but not ROCK HARD within second, I can still squeeze it to some degree

Am I good for a compression test? Any other way I could test the HG or anything else that could explain this? Thermostat seems to be working fine, the level of coolant is: filled to the top in radiator, filled to just under Full in the overflow when checking in morning stone cold.

Any help appreciated..
 
You can’t see the video? weird it works for me when I log myself out of reddit. Let me try to put it somewhere else
 
Ok does this work
I guees coolant expends as it heats but I may be worried a little haha

 
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This is the overflow tank after a 8mn drive. Just shaking under the engine (and Im wondering if it wasn’t the case as well around the rad, first video Ive uploaded)



this is the top rad hose after the drive, fairly soft definitely not rock hard

 
Been driving 1000km since the incident and still paying close attention to what the cooling system is doing. My radiator looks full every 3 or 4 mornings I’ve checked it, however the overflow level seems to vary. I understand as long as the radiator is full I shouldn’t think too much about the overflow that can vary for a various number of reasons.

Now as I replaced the top radiator hose, it feels firmer than the previous one obviously, but still squeezable. When I turn on the engine from cold, it gets harder gradually but pretty instantly (not rock hard I can still squeeze it but definitely much harder than when engine turned off and cold). Is this normal behaviour? Is the system already under enough pressure you could notice it on the hose a few seconds after starting? It gets even harder when engine is hot but I know this is normal. Just wanted to get an indication of how this hose should feel.

Also, I consider something “rock hard” when I can’t squeeze it at all, like the truck’s tyres for instance…just for reference and understanding. It doesn’t feel like this after seconds (or ever), but just harder.

Thanks for the help as always!
 
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