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

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Just as Im reading your post Im getting some ads from JRP trying to force me to buy their product haha, well perfect to actually have them next to each other to compare the design and I can confirm I prefer the minimalistic style of Engine guard vs all the flashy lights which definitely don’t fit inside of a 30 yo - all stock- sorta truck haha. Will order one now.

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Good that you caught it before the gauge went into the red — the 1FZFE is generally pretty tough but overheating will stress the upper radiator tank and the head gasket in that order. The top tank cracking is probably exactly what happened here, those aluminum tanks don't like heat cycles they weren't designed for. What you're describing with coolant appearing at that right-side corner after a long highway run (enough pressure to weep through a hairline crack) fits that pattern exactly.

The top radiator hose feel you're describing — firms up quickly from cold but still squeezable — sounds normal to me. On a healthy system you should feel it pressurize within a minute or two of starting. Rock hard immediately from cold would actually be a bad sign (combustion gases pressurizing the coolant). What you've got sounds right.

Main thing I'd focus on now: do a proper pressure test with the engine cold, hold 13 psi for 15-20 minutes and watch the gauge. If it drops at all you've got a leak, and you can look for wet spots with the system pressurized without needing to run it. Makes finding a hairline crack much easier than trying to catch it in the act on a drive. Once you know the rad is the culprit, just replace it and be done with it. For Aus, Koyo and Denso both make solid replacements for the 1FZFE and you'll be glad you went with a quality unit.
 
jeanbono said:
Just as Im reading your post Im getting some ads from JRP trying to force me to buy their product haha, well perfect to actually have them next to each other to compare the design and I can confirm I prefer the minimalistic style of Engine guard vs all the flashy lights which definitely don’t fit inside of a 30 yo - all stock- sorta truck haha. Will order one now.

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I think you will like. Only issue is it reads c only. No problem for an Aussie. If I add 100 to readout I get the approximate f deg
 
jeanbono said:
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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I had to replace the radiator in my HDJ80 recently. Got an all-alloy unit on EBay from China for $380 delivered. Very solid looking unit. Also thicker than standard (4 core)
 
discoverydave said:
Good that you caught it before the gauge went into the red — the 1FZFE is generally pretty tough but overheating will stress the upper radiator tank and the head gasket in that order. The top tank cracking is probably exactly what happened here, those aluminum tanks don't like heat cycles they weren't designed for. What you're describing with coolant appearing at that right-side corner after a long highway run (enough pressure to weep through a hairline crack) fits that pattern exactly.

The top radiator hose feel you're describing — firms up quickly from cold but still squeezable — sounds normal to me. On a healthy system you should feel it pressurize within a minute or two of starting. Rock hard immediately from cold would actually be a bad sign (combustion gases pressurizing the coolant). What you've got sounds right.

Main thing I'd focus on now: do a proper pressure test with the engine cold, hold 13 psi for 15-20 minutes and watch the gauge. If it drops at all you've got a leak, and you can look for wet spots with the system pressurized without needing to run it. Makes finding a hairline crack much easier than trying to catch it in the act on a drive. Once you know the rad is the culprit, just replace it and be done with it. For Aus, Koyo and Denso both make solid replacements for the 1FZFE and you'll be glad you went with a quality unit.
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Yes correct, I wish the head of the 1FZ was like the block, cast iron rather than Alu. Once I stopped with the gauge at 3/4, and put the shroud back together, I waited 15mn and started the cruiser, was able to drive another 20mn home in traffic and the gauge was back where it should be! Crazy that after going fairly hot (gauge only moving when over by 50 deg C) and losing some coolant (it was still between low and high in expansion tank not sure about the rad) the engine was still able to run perfectly. It was a bet but I had told myself that as soon as the gauge would move again I'd get a tow (and it did not). Did not want to add cold water in a very hot engine so did not touch anything.

The radiator I had was actually and OEX Brass but I agree with you that's exactly what would have happened. The one I put now is Denso, alu with plastic tanks...just like the OEM for the 1997 1FZ, hopefully it lasts some time. I've only heard good things about Denso and got it at a very good price (400 aud), could not locate a Koyo.

Noted regarding the upper hose, great to know this is all normal!

I've told myself if the level in the expansion tank/rad drops more than it did I'll pressure test. Just drove another 400km with no issue, so these small coolant variations could have been the system adjusting after a cooling system overhaul.
 
Chuck Steak said:
I had to replace the radiator in my HDJ80 recently. Got an all-alloy unit on EBay from China for $380 delivered. Very solid looking unit. Also thicker than standard (4 core)
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The Denso ones are now made in Taiwan, not Japan...so there might be nothing wrong with yours from China.
 
discoverydave said:
Good that you caught it before the gauge went into the red — the 1FZFE is generally pretty tough but overheating will stress the upper radiator tank and the head gasket in that order. The top tank cracking is probably exactly what happened here, those aluminum tanks don't like heat cycles they weren't designed for. What you're describing with coolant appearing at that right-side corner after a long highway run (enough pressure to weep through a hairline crack) fits that pattern exactly.

The top radiator hose feel you're describing — firms up quickly from cold but still squeezable — sounds normal to me. On a healthy system you should feel it pressurize within a minute or two of starting. Rock hard immediately from cold would actually be a bad sign (combustion gases pressurizing the coolant). What you've got sounds right.

Main thing I'd focus on now: do a proper pressure test with the engine cold, hold 13 psi for 15-20 minutes and watch the gauge. If it drops at all you've got a leak, and you can look for wet spots with the system pressurized without needing to run it. Makes finding a hairline crack much easier than trying to catch it in the act on a drive. Once you know the rad is the culprit, just replace it and be done with it. For Aus, Koyo and Denso both make solid replacements for the 1FZFE and you'll be glad you went with a quality unit.
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ChatGPT doing its thing haha
 
Update: drove the engine hard for 700km and coolant level seems to have stabilised in the overflow tank after checking yesterday after the drive and this morning, that feels good.

Noticed drops of coolant on top of reservoir and I’m pretty sure it’s because the cap doesn’t seal well anymore. Wonder how it makes its way through considering its not even pressurised but anyway will see if I can just replace cap or need to get an overflow tank assembly.

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Just got a new expansion tank + cap. Would you just remove old bottle in morning with cold engine, refit hose to radiator, then refill new bottle with matching coolant to the level it was? I've got 50/50 mix concentrated + distilled water green coolant in the system right now, can I just fill overflow bottle with green premix? Same type of coolant but different brand should be fine yeah

Thanks
 
jeanbono said:
Just got a new expansion tank + cap. Would you just remove old bottle in morning with cold engine, refit hose to radiator, then refill new bottle with matching coolant to the level it was? I've got 50/50 mix concentrated + distilled water green coolant in the system right now, can I just fill overflow bottle with green premix? Same type of coolant but different brand should be fine yeah

Thanks
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yes, correct
 
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