tenchu

I broke a nipple off one of my sensors today on accident (old and brittle).

It is the sensor just to the left of the drivers side fuel rail, with two teal nipples coming off of it:



Also, can anyone give me a list of coolant sensor locations and jobs? I know there are multiple coolant sensors on this car, and each "read" or "do" something different. I replaced the "popular" coolant sensor behind the passenger side cam, but my car is still running hot. I did the timing belt/water pump service about 4,000 miles ago (all OEM parts), and the temp still rises. The car will never over heat, even at a stop, but it rarely runs at a "normal" temp unless its below 50*F. It generally runs in-between the middle and the line right before it turns red, and if it sits for too long, or its a very hot day, it will sit right at the line before the red zone.

Coolant was changed, and bled after doing the water pump, thermostat is opening as well, so i'm not sure what the deal is, i'm thinking maybe theres another coolant sensor thats faulty.

No coolant in the oil, no loss of coolant, no oil leaks, no burning oil.

Oh, and this is a 1990 LS400 w/ 260,000 miles on the clock

fencera

My understanding is that there are three sensors:
1. You replaced one... signal goes to ECU. Affects idle, mileage etc etc
2. small gold one very close to the one you replaced... this goes to instrument cluster display
3. one in the radiator (lower driver's side I think) this turns on the condenser fans

It sounds as if your fan clutch may be broken. Does your fan blade spin freely by hand? Good luck.

tenchu

Thanks! My fan blade (with the car off) will turn about the distance of a blade width with a good push from my hand, but its not "free spinning" as if there was no tension. Is this supposed to be this way?

Also, any clue what sensor that is that I just broke? In the picture its right above where the upper radiator hose would connect, just to the left of the fuel rail, and has two teal nipples coming off of it.

Thanks for the response!

fencera

The fan blade resistance sounds right.

I missed the text above the pic in your post. What you broke is your "vacuum switching" valve #1 part no 90925-05068 for 1989.05-1990.08 or 90925-05075 for 1990.08-1992.08. Probably not the cause of the "overheating" though, this has to do with vacuum egr etc.

I've broken one of these before (and since replaced it with little notice)... actually think I have an extra laying around. No idea what it does exactly aside from "vacuum switching" and I think I was driving for quite a while with mine basically put back together with silicone sealer after it was broken many years ago. Depending on how yours broke, you may be able to do something like that taking care not to clog the holes.

If everything was done as you described in your post and, as you described, your fan works correctly, I'm not really sure about the overheating. Does turning the heat on have any effect? Last time a coolant flush was done/has the coolant been regularly changed? I'd say it's definitely a sensor, but the fact that it seems to correlate to times when the cooling system would be otherwise "stressed" is cause for concern...

tenchu

Yeah, I just zip tied the line onto whats left of the nipple on that part for now. Thanks for the PNs

When I did the water pump/tbelt I drained all the coolant and replaced with brand new 50/50 mixture. Turning the heat on does help a bit with the temp, which kind of leads me to believe the temp gauge is indeed reading correctly. The only thing I can really think that would make sense, if it is not a sensor, is the fact that I don't have a radiator fan shroud. I've been scoping junk yards but haven't found one yet, but I can't see this making that huge of a difference?

fencera

There are a few shrouds on ebay. I replaced the one on my car with a new one and noticed little, if any difference. I doubt that's the problem...

I don't know the history of the car, but is it possible you need to flush your coolant system as opposed to a drain and fill? ie is the radiator filled with crap? What condition was the coolant you took out? Did you remove the bottom radiator hose when changing the coolant to check for debris? I had a minor problem with my original radiator and replaced it with a koyorad and it has been fantastic. Not saying that is your problem for sure, but if I was going to start looking at the problem more carefully, I'd probably start with the radiator's internal condition knowing what you do now.

deanshark

A new fan shroud wont help you out at all with the cooling of the engine. It's only there for safety, to protect against chopping off a hand or something. Are your radiator fans turning on? It sounds like they're not working b/c it gets cooler as you drive, meaning there's air blowing on the radiator which stops the temp from going up and when you're stopped there's no air cooling it down. You could also have either a bad gauge or a bad gauge sensor. I really don't think it has anything to do with the coolant itself, unless there's not enough in it and you have air. Try bleeding the system again and adding a little more coolant.

tenchu

Changed the tstat today and did a cooant flush with the machine at work, still running hot, now that its warmer outside (90s) the car sits at the line right below the red, ON the line when I'm sitting still. The electric fan on the pass side comes on when the AC is on, but the drivers side never comes on, I can't see the ac fan making this huge of a difference?