Been battling my 85 Running hot for a while now. New radiator, thermostat, fan clutch, hoses. Runs fine in town and around town but when I run it 20+ min with time on the highway or in traffic it starts running too hot and hot red on gauge the other day. Torfab did the radiator work and 2 compression tests and hydrocarbon test like 2 months ago and passed all so probably not a head gasket. What else could it be?
85 Running Too Hot only Highway (1 Viewer)
- Thread starter seattlefj60
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tmxmotorsports
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No mention of water pump who installed the thermostat?
- Thread starter
- #3
Yeah was wondering if water pump would be next. I installed the thermostat...was pretty straightforward but I'm a 
type of mechanic...could it be that?
type of mechanic...could it be that?
tmxmotorsports
SILVER Star
Did you use oem thermostat with gasket and rubber seal?
- Thread starter
- #5
This one from Cruiser Corps and yes gasket and rubber seal. Maybe this is not oem or just faulty? I guess it would be easy to buy another and retry. Thermostat FJ40, FJ45, FJ55, FJ60, FJ62, FJ80 1958-1992 - https://cruisercorps.com/products/thermostat?variant=12736751566914
What @DrRock said.
I have an '85 FJ60 also and recently refreshed my coolant system for exact same issues. My stock temp gauge did the usual spike towards high but normal temps via my IR gun. I had changed the water temp sending unit, water pump, and have a HD fan clutch as well. Radiator has no leaks. Because of the stock temp gauge always showing 'elevated' temperature but normal temps with the IR fun, I put in a Koso unit (got idea from @HemiAlex) and its probe is in the BVSV port location. Perfect location for the cig lighter location using the awesome @TRAIL TAILOR bezel (which will likely last well after the rig has decayed lol).
Due to location BVSV probably gets the highest readings and the highest I’ve got was 212 (during summer) but even then with use of IR gun the rest of the engine and the rad hose was never above 200. The 212 was after 30 min highway run at 70 and then idle. Temp dropped to 190 after 1-2 minutes. Can also consider upper rad hose if you go similar route.
The stock gauge will just not be accurate most likely.
I have an '85 FJ60 also and recently refreshed my coolant system for exact same issues. My stock temp gauge did the usual spike towards high but normal temps via my IR gun. I had changed the water temp sending unit, water pump, and have a HD fan clutch as well. Radiator has no leaks. Because of the stock temp gauge always showing 'elevated' temperature but normal temps with the IR fun, I put in a Koso unit (got idea from @HemiAlex) and its probe is in the BVSV port location. Perfect location for the cig lighter location using the awesome @TRAIL TAILOR bezel (which will likely last well after the rig has decayed lol).
Due to location BVSV probably gets the highest readings and the highest I’ve got was 212 (during summer) but even then with use of IR gun the rest of the engine and the rad hose was never above 200. The 212 was after 30 min highway run at 70 and then idle. Temp dropped to 190 after 1-2 minutes. Can also consider upper rad hose if you go similar route.
The stock gauge will just not be accurate most likely.
OCD Trigger Alert!
- Thread starter
- #9
So the gauge is always wrong or you're suggesting it has degraded and might be failing now? I have had the same gauge since I bought like 6 years ago and it's worked fine and operated at like 30-40% when hot until after 8 months ago when my cooling system problems and refresh began. Before I got a new rad it showed overheating when it was overheating (smoke and coolant dump as proof) thus the new radiator. Tldr I'm hesitant it has always just been like that.
Are the symptoms inline with a faulty thermostat or my water pump?
Are the symptoms inline with a faulty thermostat or my water pump?
No conclusion can be drawn until you get a 2nd reliable temperature gauge.
Maybe the engine is getting hot, but there’s no way to know for sure if using the original Toyota gauge.
Here’s one tip: If the coolant temperature really is in the red, (over 245°F) if you turn on the heater, the air blowing out of the vent will actually burn your hand. It’ll feel like a propane torch.
Maybe the engine is getting hot, but there’s no way to know for sure if using the original Toyota gauge.
Here’s one tip: If the coolant temperature really is in the red, (over 245°F) if you turn on the heater, the air blowing out of the vent will actually burn your hand. It’ll feel like a propane torch.
lol, yeah totally OCD - but honestly when the temp gauge keeps spiking it’s hard to relax until you get an accurate temp gauge in there.
@seattlefj60 - as OSS says, hard to know until you get another temp gauge reading - if your temps are actually fine then it’s likely just your OE temp gauge. Mine too worked fine for the first 6 years I had it too until it didn’t. You can get an IR gun for cheap and get readings. If temp is actually fine then there isn’t much to do outside of getting a secondary gauge (especially if you can’t relax like me looking at the OE gauge spiking).
I didn’t replace my radiator because there doesn’t seem to be anything wrong with it outside of the OE gauge.
@OSS and @Spike Strip are really knowledgeable and can likely weigh in on how the OE reading actually works and what it would take to fix it - I’m just a simpleton (but it still is a rough measure and not really accurate).
@seattlefj60 - as OSS says, hard to know until you get another temp gauge reading - if your temps are actually fine then it’s likely just your OE temp gauge. Mine too worked fine for the first 6 years I had it too until it didn’t. You can get an IR gun for cheap and get readings. If temp is actually fine then there isn’t much to do outside of getting a secondary gauge (especially if you can’t relax like me looking at the OE gauge spiking).
I didn’t replace my radiator because there doesn’t seem to be anything wrong with it outside of the OE gauge.
@OSS and @Spike Strip are really knowledgeable and can likely weigh in on how the OE reading actually works and what it would take to fix it - I’m just a simpleton (but it still is a rough measure and not really accurate).
I went from an original radiator, where my temp never went above 195 no matter the conditions, to a CSF. My highway temps immediately went to a consistent 210, and around 220 when climbing the long passes we have in Colorado.
Caveats:
-I completely refreshed the cooling system when the original radiator was in and ran like that for close to two years. Long enough to know that 195 was the stabilized temp for any driving, in any weather.
-Original radiator sprang a leak, hence moving to a CSF
-I have a temp sensor in the upper radiator hose. Gauge is on a pod in the cabin so I can see it while driving.
I agree with the consensus that you need to get an accurate temp reading. The stock gauge is fairly worthless.
Caveats:
-I completely refreshed the cooling system when the original radiator was in and ran like that for close to two years. Long enough to know that 195 was the stabilized temp for any driving, in any weather.
-Original radiator sprang a leak, hence moving to a CSF
-I have a temp sensor in the upper radiator hose. Gauge is on a pod in the cabin so I can see it while driving.
I agree with the consensus that you need to get an accurate temp reading. The stock gauge is fairly worthless.
- Thread starter
- #13
Thanks all...this makes total sense and I now have an IR gun on the way to check for real. Also have an OEM thermostat and gaskets on the way in case. I'll follow up. Appreciate the advice...thank you.
As others have said, a secondary (accurate) temp gauge is mandatory. The stock gauge is notorious for having issues when the Voltage meter circuit goes wonky (there's a long thread about it). @Spook50 was working on a replacement fix but I don't know the status.
An IR gun helps to check the temperature of the head when your gauge reads hot (it won't be exact, but you'll see if it's really running hot by checking rad hoses, various places on the head, thermostat housing, and especially stock sending unit location).
Usually Fan Clutch and Water Pump are replaced together for prevention. Running hot is prolly the worst thing you can do to these I6 engines.
New radiator (Genuine) cap?
An IR gun helps to check the temperature of the head when your gauge reads hot (it won't be exact, but you'll see if it's really running hot by checking rad hoses, various places on the head, thermostat housing, and especially stock sending unit location).
Usually Fan Clutch and Water Pump are replaced together for prevention. Running hot is prolly the worst thing you can do to these I6 engines.
New radiator (Genuine) cap?
- Thread starter
- #15
Yes new cap. Didn't replace water pump when I replaced fan clutch just because I didn't have much time and also have never done before so was nervous about trying it haha.
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- #16
Here's what my IR gun shows in various places after a 30 min drive and the gauge showing 75-80%. I assume this means temp is ok and my gauge may be suspect?
- Rad 180
- Upper rad hose 186
- Thermo housing 165
- Head near oil cap 165
- Head passenger firewall 178
- Head cover by carb 190-238 (jumps all over sometimes over 300 but maybe I'm hitting the ceramic manifold which gets hotter?)
- Rad 180
- Upper rad hose 186
- Thermo housing 165
- Head near oil cap 165
- Head passenger firewall 178
- Head cover by carb 190-238 (jumps all over sometimes over 300 but maybe I'm hitting the ceramic manifold which gets hotter?)
What temp thermostat did you use?
- Thread starter
- #18
I would assume the same, What was ambient temp (approx)?
- Thread starter
- #20
Got it. Do you mean in the cabin coming out of the heat vent? If so I had it on and it was not hot...more like warm.
