salimshah

My son's 95 SC400 130kmile is not taking well to the onset of summer. I replaced the radiator with OEM last year and the water-pump a few months back [hard lesson learnt as I did not replace the wp with timing belt]. Replaced the radiator filler cap. Tested the new cap to be around 8psi [uncalibrated test equip] [spec calls for 8-13psi]. Age related things like loss of mirror control ecu has happened.

In slow (stop and go) traffic the temp gauge starts creeping up. As soon as I get going in less traffic the gauge comes back to normal.

I suspect the problem is due to air flow and suspect the speed of the hydraulic fan is not kicking up.

Book say to short DLC1 posts E1 and OP1 and the fan speed will be around 1k rpm. I dont have a strobe and do not know how much of storm to expect.

Few things I have done is let the engine cool down.
Put the jumper. Started the car (without touching the gas pedal) and observed the speed of the fan. Pulled the jumper and noticed no change.
Got back in and turned the AC on and when I got back to the engine bay it appeared to me as if the fan speed was faster [single person observation with time lapse] . The observation is counter to expectation so at this time I am attributing it to my incorrect perception [will try again with two ppl].

Should I try throwing a used fan control ECU?


Open to suggestions.

Salim

canman44

Have you replaced your thermostat and purged any air from the system?

salimshah

Thank you for bringing it up

Forgot to list that as already done. I have not replaced hoses though. They feel OK, No bulging no soft spot and definitely not rigid.

Clues warming up and reaching the desired operating temp are good.
Radiator part is warming and getting hot.

Some thing is going on that my logic is not helping me narrow down.

Salim

Ali SC3

iTrader: (10)

here are a few threads that sound like your problem, you likely still have air in the radiator or have a coolant hose end or something leaking now that the system is able to pressurize again.
the sc400 is a hard system to get all the air out, blast the heater, reburp the system, it will probably take some more coolant and then stop doing it. are you getting hot air right now (i know its summer but try the heater), if you are not getting hot air that is a tell tale sign a sc400 is low on coolant.

https://www.clublexus.com/forums/per...erheating.html
https://www.clublexus.com/forums/per...g-problem.html
https://www.clublexus.com/forums/per...tion-help.html

salimshah

Thanks for all the help.

I did confirm that there is no air in the coolant.

I think the fan is not kicking up in speed. Started the car with cooled of engine ambient 80+ (this is central Texas).

Parked in the garage and let the beast warm up. Reached the operating temp and the fan speed never changed. But the temp did not get higher than op temp.

Will try again during the day.
Will also try to jump the heat sensor switch to see instant jump in speed. [test point did not work for me and not having a strobe I can not tell if the fan is already running high].

Side note: It was fun reading the confusion about the temperature sensor and temperature switch. Immense amount of confusion running around on the net.

Wish me luck.

Salim

salimshah

Success!

I had to rip open the dash and tested for ohmage on solenoid pins at the Fan ECU. It was open. Turned out the connector at the solenoid needed cleaning. An after affect of corrosion that set in after a busted radiator and water-pump.

Knowing your car is important as once the terminals were clean and I jumped the test points, the fan kicked in with a storm. Now I know what to expect.


Thanks for all the help.

Salim

M.Rad.

Salimshah- it seems I have the same problem you had (I am also in CenTex).

The car stays at proper temp while at speed with the A/C on, but starts getting hot when I slow down for city traffic (up to 2/3 on the gauge). It cools back down once I get back up to highway speed.

My fan works but doesn't speed up when the engine starts getting warm. I jumpered the diagnostic pins and got no difference in fan speed.

I would like to check the solenoid and wiring, but have not been able to locate it. I spent an hour under the car and under the hood, removed the air box etc. but could not locate it. Do you have any links to pictures or diagrams showing what to look for?

Regards,
M.R.

zneubauer

iTrader: (2)

When I lived in FL I had a similar problem with a few cars and it turned out to be the rad fan/switch. You can either replace everything oem/used or you can buy a fan switch kit, which is what I did and it worked great. It sounds like you're on the right track and at the very least, you'll have a brand new, flushed and working cooling system.

salimshah

MRAD and I exchanged PM.

In case some one else runs into this problem, the solenoid is the long cylinder thing sticking out of the serpentine belt pathway [SC400] on the pump itself. The wires sneak past the belt path and make a connection through a connector attached to the timing belt cover (driver side bank). Access is easier if you remove the battery (not really needed).

I am pretty sure this connector is talked about in the t-belt replacement process [the cover needs to be removed to access the t-belt].

Fall is about to come [ha ha still around 100 here in Sept] and have had no issues since the fix


Salim

M.Rad.

Many thanks to salimshah for his advice. I still have not had time to troubleshoot the fan speed problem, although I now know where to look.
What I DID do was to raise the front of the car, turn on the heater and re-bleed the cooling system. This seems to have taken care of the problem even without the fan speed increasing.

I recently had the opportunity to run the car at over 90mph for 15 miles in 95*+ heat with the A/C on (we have an 85 mph toll road here in TX) and the temp stayed rock steady at one needle width over the 40% mark (I think this is equivalent to about 210*F).

Also, I can leave it at idle with the A/C on for as long as I like and the temp stays steady there too.

I will eventually track down the fan problem and report to the board, but for now all's well!

Regards,
M.R.