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.

View attachment 4109078
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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!

View attachment 4093729

View attachment 4093730
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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.

IMG_7519.webp
 
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
 
Hi all,

Long post but to summarise and make it easy. Saw some coolant on top of overflow reservoir as previously mentioned. Cap was very easy to remove and not sealing properly as the new cap is really tight. Was hoping this would fix my slow coolant loss but it did not. Just a summary of everything as this coolant loss is a mystery.

Cause: my engine slightly overheated (did not hit the red). Ended up cracking the radiator.

What was done, a coolant overhaul:
-PHH replaced (prior to event)
-All coolant hoses pretty much replaced
-New radiator (Denso)
-new fan clutch
-new thermostat
-new fan shroud
-new overflow bottle (i just replaced that a week ago)

What’s happening:
-coolant in the overflow is dropping very slowly. Ive lost the equivalent of 1cm of coolant (measured in the overflow) last 3000 km. Obviously not ruling HG but:

-no white smoke
-oil and coolant really clean
-no bubbles anywhere
-no pressure in hoses
-exhaust smells like exhaust
-drives great
-system works perfectly fine overflow goes up and down.
-radiator is always full in morning

Been going under the car when idling and can’t find any dried blue residue except around the oil pump area (weird) as per picture.
I’m getting a pressure testing kit tomorrow as next step to see if I can make some coolant drip which is what I want to see the most lately.

After this it will be checking spark plugs and all the other HG test but I just can’t see the engine having a HG leak as minor as it could be and absolutely not a single other symptom.

Any thought? Water pump is next culprit but it’s hard to see anything without removing anything, not sure where that weep hole is btw?

Any help much appreciated.

1fzfe - 300 000 km - 1997

IMG_8324.webp
 
jeanbono said:
Hi all,

Long post but to summarise and make it easy. Saw some coolant on top of overflow reservoir as previously mentioned. Cap was very easy to remove and not sealing properly as the new cap is really tight. Was hoping this would fix my slow coolant loss but it did not. Just a summary of everything as this coolant loss is a mystery.

Cause: my engine slightly overheated (did not hit the red). Ended up cracking the radiator.

What was done, a coolant overhaul:
-PHH replaced (prior to event)
-All coolant hoses pretty much replaced
-New radiator (Denso)
-new fan clutch
-new thermostat
-new fan shroud
-new overflow bottle (i just replaced that a week ago)

What’s happening:
-coolant in the overflow is dropping very slowly. Ive lost the equivalent of 1cm of coolant (measured in the overflow) last 3000 km. Obviously not ruling HG but:

-no white smoke
-oil and coolant really clean
-no bubbles anywhere
-no pressure in hoses
-exhaust smells like exhaust
-drives great
-system works perfectly fine overflow goes up and down.
-radiator is always full in morning

Been going under the car when idling and can’t find any dried blue residue except around the oil pump area (weird) as per picture.
I’m getting a pressure testing kit tomorrow as next step to see if I can make some coolant drip which is what I want to see the most lately.

After this it will be checking spark plugs and all the other HG test but I just can’t see the engine having a HG leak as minor as it could be and absolutely not a single other symptom.

Any thought? Water pump is next culprit but it’s hard to see anything without removing anything, not sure where that weep hole is btw?

Any help much appreciated.

1fzfe - 300 000 km - 1997

View attachment 4129280
Click to expand...
Look at the o-rings on the bypass piece above the thermostat. It is a cast aluminum pipe that bolts to the head and has 3 o-rings and a sleeve on the bottom. It took me 3 years to finally see a wet spot at the bottom of that area.
Buy 3 new o-rings, a new sleeve, and maybe even a new casting piece if you're feeling like spending money instead of time to clean it up.
Use Scotch-Brite pads to scrub inside the cast piece below to make sure it gets cleaned out. Use fresh antifreeze as a lubricant to put it all back together.

There are a couple write ups on here as well as the FSM.
 
Thanks BILT4ME, will check that!

Haha I do drive it CJF proof is I just did 3000km in a bit more than a month. A coolant leak is never to be overlooked though, I don’t see this as obsession just care for something valuable to me, I don’t stress about it but want to get to the bottom of it.
 
jeanbono said:
Thanks BILT4ME, will check that!

Haha I do drive it CJF proof is I just did 3000km in a bit more than a month. A coolant leak is never to be overlooked though, I don’t see this as obsession just care for something valuable to me, I don’t stress about it but want to get to the bottom of it.
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My next move would be a cooling system pressure test. That would have actually been my first move. Then combustion leak test (co2) for the head gasket, and then a compression test (or even leak down test) pending the results of the first 2 tests.

I have spoken to a handful of people who ended up having a head gasket issue with the same symptom of ever so slowly losing coolant from the overflow. This slowly got worse overtime until it was obvious what the issue was. I'm in this current position. I had an overheating event, refreshed the entire cooling system, and since then, I've been slowly losing coolant from the overflow. I may have previously mentioned, that you're bound to lose some initially over the first 800km as the system "burps".. it's a massive cooling system, and I don't care what anyone says about the design, you DO get air in it after draining and replacing radiators, block etc. The question is, has it stabilised or does it continue to drop..

Mine for example, dropped 3cm rather quickly, and now it's possibly stabilised. Like you, I have zero other symptoms, car drives perfectly, doesn't overheat, no smoke, no oil in water or vice versa, just this slow coolant loss and an oil analysis test that showed severe levels of potassium, which would normally indicate antifreeze in the oil, but to complicate it further, my vehicle is dual fuel LPG and the valvesaver fluid it uses for that has really high levels of potassium.. so it could be from that. I don't drive the truck much, so it's taking me a long time to see the rate of coolant loss or if it's finally settled. I've stopped the valvesaver fluid, and plan to do another oil analysis around the 1,000km mark. We also did the co2 test before dismantling and replacing the cooling system, and the result was negative. We then did a cooling system pressure test after replacing the radiator etc, and it held steady pressure overnight.

Even if you're not a mechanic, an oil analysis, cooling system pressure test, and co2 combustion leak test are all extremely easy to do, and the equipment is cheap. If you were in Sydney, I'd give you a hand, as I have a combustion leak tester and compression tester. I almost bought a cooling system pressure test, but my mechanic never charges me to do it, so I drew the line there as it's the more expensive of the 3.
 
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petegangies said:
My next move would be a cooling system pressure test. That would have actually been my first move. Then combustion leak test (co2) for the head gasket, and then a compression test (or even leak down test) pending the results of the first 2 tests.

I have spoken to a handful of people who ended up having a head gasket issue with the same symptom of ever so slowly losing coolant from the overflow. This slowly got worse overtime until it was obvious what the issue was. I'm in this current position. I had an overheating event, refreshed the entire cooling system, and since then, I've been slowly losing coolant from the overflow. I may have previously mentioned, that you're bound to lose some initially over the first 800km as the system "burps".. it's a massive cooling system, and I don't care what anyone says about the design, you DO get air in it after draining and replacing radiators, block etc. The question is, has it stabilised or does it continue to drop..

Mine for example, dropped 3cm rather quickly, and now it's possibly stabilised. Like you, I have zero other symptoms, car drives perfectly, doesn't overheat, no smoke, no oil in water or vice versa, just this slow coolant loss and an oil analysis test that showed severe levels of potassium, which would normally indicate antifreeze in the oil, but to complicate it further, my vehicle is dual fuel LPG and the valvesaver fluid it uses for that has really high levels of potassium.. so it could be from that. I don't drive the truck much, so it's taking me a long time to see the rate of coolant loss or if it's finally settled. I've stopped the valvesaver fluid, and plan to do another oil analysis around the 1,000km mark. We also did the co2 test before dismantling and replacing the cooling system, and the result was negative. We then did a cooling system pressure test after replacing the radiator etc, and it held steady pressure overnight.

Even if you're not a mechanic, an oil analysis, cooling system pressure test, and co2 combustion leak test are all extremely easy to do, and the equipment is cheap. If you were in Sydney, I'd give you a hand, as I have a combustion leak tester and compression tester. I almost bought a cooling system pressure test, but my mechanic never charges me to do it, so I drew the line there as it's the more expensive of the 3.
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Thanks mate appreciate the insight, yeah I daily driver my cruiser so I can tell a bit more than you, it’s so slow though. Ive just got a pressure tester today finally..onto it tomorrow morning and will go from there! Where did you do the oil analysis in Australia? Ive been looking and couldn’t find a spot to do it.

Appreciated the help but I’m on the south coast
 
Also how could it hold pressure overnight and you could still lose coolant/have a HG issue? I was going to test over 20mn but you reckon overnight more accurate then? I hope to see some coolant drip on my garage floor tomorrow haha
 
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