1994 80 Series Running Hot (1 Viewer)

[coreygil18]

I am new to IH8MUD and love the content and help so far. I have a 1994 with 4.5l 1fz engine. It has been running a bit hot (half way between mid and red on gauge) when climbing hills only. Recently it started to jump up close to red. Even started doing it periodically on flat ground. Granted it is 115 here in Phoenix now. AC starts to go warm as the temp rises close to the red zone. Car cools down going down hill or even after I cycle the AC on and off a few times. Radiator pulls from the reservoir when hot, nearly empties it. I have drained radiator, replaced cap, replaced Thermostat. I see and detect no coolant leaks. Drained coolant was clean. I also did a combustion gas leak test and it was negative. Running idle in driveway doesn't overheat. Fans come on with and without AC. Coolant is flowing through upper and lower radiator hoses well. AC compressor doesn't appear to seem to seize when idle in driveway.

Needless to say I am stumped on what to check next. Any help or ideas will be appreciated.

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[SpenserAK]

Did you use an OEM cap & t-stat?

Water pump?

Confirmed actual temps with a scangauge/etc? The stock gauge is more of a dummy light, but any creeping above normal indicates something is going on.

How old is your radiator?

Fan comes on, but maybe the clutch needs attention?

Hills in hot weather will test your cooling system, but a good system should handle it.

 

[coreygil18]

I used an OEM t-stat. I have after market radiator and used after market radiator cap. I didn't confirm temps with a scanguage yet. Fans are dual electric fans. Radiator is fairly new. I don't know exactly. was installed prior to purchase.

 

[Marco Lau]

fan clutch, radiator cap, waterpump, thermostat...could be anything. hopefully your HG is not cooked......

 

[azngarage]

May be the dual electric fans dont provide enough cooling for the engine.

 

[BILT4ME]

I used an OEM t-stat. I have after market radiator and used after market radiator cap. I didn't confirm temps with a scanguage yet. Fans are dual electric fans. Radiator is fairly new. I don't know exactly. was installed prior to purchase.

Do you still have a stock fan and fan clutch installed including the electric fans?

You need to check what turns on the electric fans. That is not stock.

The fan clutch needs a heavier cst oil in it if it is still on the truck.

 

[Broski]

My stock gauge doesn’t move tell the temperature reaches 218-220.
The ac cuts out a 226 so if the ac goes warm the the temperature is up there !

 

[jpoole]

Radiator pulls from the reservoir when hot, nearly empties it

Typically when the engine is hot the coolant level in the overflow reservoir will go up then as the engine cools the level goes back down. Is what you wrote above a typo? If not seems like there's a problem/clue here.

I'm not sure what type of cfms you are getting with those electric fans but if all else is in good order I wonder if those are also an issue. One way to get insight into this would be to watch the actual temps (odb2 sender/scangauge/etc.) and then monitor temps at different driving speeds to see if passive air flow changes the temps. By passive I mean air flow that's not from the fans but from moving the 80 through the air. My memory on the speeds/cut-offs may not be that accurate but I do recall that when my fan was performing poorly that temps would climb at low (stop and go traffic) and high (interstate 70+) speeds as air stopped moving through the rad as much. Watching to see if temps drop in the 40-50 range may be a good way to see if increased airflow drops temps quickly/consistently.

Once tuned up properly I've had very good cooling with the blue hub fan clutch on my 80 including towing a 3k lb camper through NM, etc. last Summer in pretty hot temps. I think many others have had similar performance with stock type setups in your area.

 

[SpenserAK]

Thought that was odd too, the res emptying when engine warms up. It shouldn’t have room to get sucked in if the system is already full. Air pocket? Did you properly burp it (at least enough) after refilling? Or maybe, are you losing coolant somewhere?

 

[robnicko]

fan clutch, radiator cap, waterpump, thermostat...could be anything. hopefully your HG is not cooked......

plus make sure the cooling system is bled of any air, use genuine rad cap ive found some aftermarket ones dont seal as well beneath the spring and coolant flows to & from the overflow before the temp / pressure its meant to
for it to almost empty the overflow, does it return once cooled down to the same level prior to overheating? - good indicator of air getting in, probably past the cap


love the rx3 Marco, I used to have an RX4 coupe

 

[SaturnAscends]

Is the oil level stable? You might wanna send out a sample to Blackstone to check for traces of antifreeze.

 

[GeoRoss]

His is a 1994, OBDI

Make sure the electric fans are working. Mechanical seems to be better here though. Aftermarket radiator caps have been problems for people in the past. Are you losing coolant?

After all that is confirmed it is down to the radiator or thermostat. You could do a pressure test and also check for exhaust gas in the coolant.

 

[Desert Dino]

I use toyocom to read real time temp plus installed dry temp sensor on the engine head

Realtime ODB1 Scanner for 94 FZJ

I’ve read through multiple threads on this, but cannot find any of the ToyoFan or Toyocom units for sale. What is available nowadays? Do any of the ODBi to ODBii adapters work with ODBii scanners? I’m mainly looking to monitor coolant temperatures in real-time.

forum.ih8mud.com

 

[Desert Dino]

with the help of Tools R Us - https://forum.ih8mud.com/members/tools-r-us.3869/ RIP I solved my problem and i am from Israel or IsraHell very hot country

1FZ-FE The Big Overheating Experiment. TESTED SOLVED!!!

ON December 2017 I posted this thread https://forum.ih8mud.com/threads/help-on-the-verge-of-despair-1fz-fe-overheating-on-flat-highway-over-60-miles.1032056/#post-11389186 It was winter time and I didn't like the temperature I was reading on my OBD and the dry contact thermometer installed on...

forum.ih8mud.com

 

[coreygil18]

Update. Tried several caps, no change. Checked oil for antifreeze, none. Then realized aftermarket radiator didn’t have a port for the small hose on top “steam line i have heard it called”. Replace radiator with stock and did water pump while in there. Problem solved! Funny how previous owner put that i without proper fitting. The line was just capped off!