Radiator coolant light will not go out

[Asianbond]

Coolant level ok, new pressure caps, oil & water temperature ok. Car drives fine, but occasionly the radiator coolant comes on and it won't go out. And I think when it comes on it retards boost to only .5 lbs.

Any ideas?

[cnh1990]

Did you check the sensor wire going to the header tank? It may have fallen off as in my case or the actual sensor in the header tank is a corroded.

[newburymess]

You are correct about the coolant sensor. When it senses low coolant level, the ECM does not allow boost to exceed .5 bar. The sensor is likely the culprit, but check the connections and use dilectric grease when re-connecting.

Scruffy Steve

[95LOTUS]

Funny this should come up...I have the same probably after replacing the header tank on my S4S. The sensor looks orangish-brown, and kinda rough...AND VERY FREAKING SMELLY!!! I can't stress the latter enough... Anyway, Lotus apparently didn't wire the sensor (atleast on my car anyways) so that it wasn't failsafe. If I leave one of the wires off, the light goes out and I get full boost. When I reconnect the wire, the light comes on and boost is cut back.

Question...is it okay to clean off the sensor? I know it sounds funny, but I'm not sure just what kind of sensor it is and I didn't want to destroy it.

Any special considerations when cleaning it?

thanks,
Bill
'95 S4S

[fmxa]

I had the same issue on my S4s. Its the coolant level sender in the header tank. Its simpler and more cost effective to just replace it (unless you've got a lot of time on your hands!). Cost about $60 and 10 minutes to install. There was a thread about this exact topic on the turboesprit list last summer

[Asianbond]

My 93 has the old style of two header tanks for the chargecooler and radiator. Is the sensor at the bottom of the black radiator header tank? How do you get to that sensor? I feel the wires on the bottom.

[cnh1990]

I will have to take a look when I get home. It's been a while since I cleaned out my tank. I did not replace my sensor. I disconnected the header tank from the system put caps on the ends and used a mineral descaler (CLR) and let it soak for a while it knocked loose all sorts of sediment. I used a wet vac to suck out the junk. Then I flushed it many times with clean water. Make sure the spade connectors on the tanks are on good.

[Asianbond]

mechanic diagnose the problem as low coolant level in chargecooler tank. he filled it up but it spits out coolant thru the relief hose everytime you get on the throttle, any ideas?

[lotusman]

I had a similar problem with the low level light coming on. As it turned out, I had changed the chip to the No. 15 for my non-SE and the programming wasn't right. I ended up jumpering out the relay and let the ECM handle the sensing.

Before that happened though, I checked my header tank and found a large piece of rust. I designed a new all aluminum tank and bought a new sensor. The old one was good though rubber seal was aging. No one has talked about the other connection, the ground spade welded to the tank. I suggest you take out the header tank and check it. I also use something developed by Volkswagon/Audi called Stabilant 22A. It makes old electrical connections like new.

lotusman
'89 non-SE

[cnh1990]

Are you talking about the overflow from the header tank or the small hose comming from the chargecooler?

How many miles do you have on the car. A chargecooler pump that has lost it's impellers can go through a little bit of coolant. It normally loses a little coolant anyways. Also if filled up all the way to the top it does expand just a little and oveflow. The cold coolant level is a tad below the cap.

[Asianbond]

The chargecooler impeller was just rebuilt.

[Asianbond]

The chargecooler impeller was just rebuilt.

[cnh1990]

So are you talking about the small hose comming from the chargecooler? If so a it is just pressed on and I have seen leakage from Chargecooler on many cars as the hose is just pressed on. When the pump was rebuild was the seals replaced or just the impeller?

I suppose it is possible for coolant to slowly leak past the seals and past the aux drive unit to be vaporized in the block.

Any signs of leaking anywhere? Do you notice coolant smell anywhere? How much are you losing and at what rate?