1992 Sc400 Overheating 2023

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New Member
recently my 92 sc400 would run hot while sitting at idle (drive thru, etc.). I noticed some coolant residue on the thermostat housing and lower radiator hose so I decided to do a small overhaul. I replaced the lower rad hose, thermostat, and oem radiator.

when I started I only drained the radiator not the block to replace the parts. I also took off my IACV to clean it for a better idle (worked like a charm). when reinstalling it I ripped the hose that goes to the top of the thermostat but I thought nothing of it.

when bleeding the system I filled the filler hole on top of the thermostat until full and also made sure the reservoir was topped up. started the car with the heat on max and the heat gradually got hotter as it should. during this process I had 2 funnels, one in the filler hole and one in the reservoir to bleed air out. It got to a point where no bubbles were coming out and the car was at operating temp so I thought I was done but the temp rose one tick past the middle and was chilling there.

I should also add in that I replaced the temperature sender the one that sends the temperature to the gauge. car’s been down for a month now I need some ideas on what could be going on. there’s a very very small amount of coolant leaking from the ripped hose but I have my doubts that that would make the car overheat but you never know. oil isn’t milky, no white smoke out the exhaust, just confused where I went wrong.

any help is greatly appreciated.


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Some questions & suggestions to consider:-
That coolant in the picture looks to be a terrible colour. might be just the pic though. You can flush the block using a garden hose. The residue water left after the flush can mix with coolant added to the system.
If the top radiator hose has a leak then it must be replaced / repaired.
Do a pressure test on the cooling system at the rated value of your radiator cap. Will be 12 or 15lb. Must hold pressure at that.
I would go back to the start and fit the original temp sender. It might be possible that the new one has a different resistance range if not oem.
The new radiator! Is it rated at the same cooling capacity as the OEM, hold the same volume of coolant?
Do you have a blockage / restriction in front of the engine radiator, aircon radiator blocked?
Are cooling fans coming on and working correctly?
Get hold of a temp gauge that can gives you an accurate reading to measure to true coolant temp.
Good luck