Hi LR friends,
Recently I replaced the a temp sensor on the radiator (the one on top of the radiator) because I was seeing Check Engine light with trouble code P1118.

This pretext for this ws discussed here:
https://landroverforums.com/forum/ge...warning-45868/

Long story short: In December I had the thermostat and sensor at the bottom of the radiator replaced after seeing P1118 - the error code went away, engine temp was fine consistently in range of 195F-205F - which I assume is the expected range.

Recently code P1118 came back, temperature was higher in range 200-210F and the other sensor was replaced. Now the Check engine light is off, UltraGauge reprorts no trouble codes, but the engine temperature is consistently in range 215-225F.

Took the truck to a shop and they claim the radiator is bad. I don't trust them because recently the temperature was fine.

Thanks for comments ideas.

Jacques

 

1118 code indicates the radiator temp thermister is high, t/stat reading above 284F.
I think I read some place that if there was too much difference between the 2 temp sensors this code will show up. You might want to read up on this issue in the Rave, I recently saw it there.

 

You would be wise to use a code scanner that can read the engine coolant temp and display it. If you are above 220 you have to ask serious questions about why.

Here's what can happen with a radiator. With lack of change of coolant, sludge can build up. Can also happen if wrong types of coolants are mixed. If previous owner also tossed in a jar or two of "stopz leekz wonder bandaid in a jar" the extra sealant material will collect in the bottom rows of the radiator with the sludge and form almost a stiff paste. Not much, if any, water will flow thru it. So the radiator still takes in and puts out the water, it just can't cool it off as much because the surface area is reduced. Would be the same if you spread thick mud on all the fins for the bottom 1/3 of the radiator like buttering a slab of toast.

This can be detected by feeling the surface of the fins top and bottom, when warmed up and truck off. Should be about same temp, my indy rad shop guy says 10 - 20 degrees. If clogged, usually the bottom will be a lot cooler.

How to fix - would seem to me that with your young truck a commercial flush at a radiator shop might be in order. They will circulate a hot type of acid to dissolve the crud and flush it out. They probably will not want to take off the plastic tanks and rod it out, they are fragile. Get estimates first. A new rad can be had for under $300. You can also try your own flush (use a powder flush, they are stronger, follow directions exactly). A home brew flush is 2 gallons of white vinegar from the grocery store, use to fill system after draining, along with a gallon of distilled water. Drive around for a few days (heat makes most chemical actions speed up), then flush with distilled water. Keep in mind that any type of flush may break loose scale deposits which can clog the top inlet hose on the thermostat, so it should be removed and flushed in every direction. Small metering holes in top leg that get clogged. Don't use muriatic acid, too strong for aluminum.

 

Also, so we can be clear - the thermostat sensor that sends that code is not located at the top of the radiator, it is on the bottom passenger side . The code is that coolant reached 284F for at least 1 second. At the bottom of the radiator..... where it should be a lot colder.... this would also be about the level where 50:50 coolant and a pressure cap just can't keep it liquid anymore and steam forms.

The temp sensor near top of radiator on driver side is oil temp for transmission. Connector C0219.

As Mike said, there is another code 0126 that indicates the engine temp and radiator temp are too close together, like with a stuck open stat, or an inline stat with too many bypass holes in it.

If the engine coolant temp is being monitored on the OBDII via scanner or ultra gauge, and does not support this value, perhaps quick inspection with a point and shoot infrared thermometer of the lower outlet would be in order. Would seem like temp gauge would be high and overheat light on.

The radiator mounted sensor is a variable resistor, it goes to lower resistance as heat increases. So a small short across the cable (gunk on connector, skinned wires against frame, etc.) could make it "read" 284F when in the physical world it is no where near that.

Would just seem that if rad is 284 at the bottom, the engine would be protesting in other areas.

 

Thanks guys - Looking at the new radiator option.

 

As an fyi: I have been monitoring the temp on ultr gauge as P1118s were logged - no overheating. In fact many P1118s were logged while engine was still cool, directly after cold start. Hence I'm pretty sure the check engine came on due to the delta between radiator out / sensor and ECM were out of range. Thanks for pointing out the idea that a short may be the root cause of the trouble code as well as the reasons for why a radiator may already be bad by 50k miles. Looks like the truck did have a head gasket job before I bought it, hence I'm assuming it had heat issues before.

 

The sensor that you replaced - if it was bottom passenger side, it can make the code. If it was top driver's side, that would be oil temp warning switch (not sensor) for the tranny - shares a warning light with the transfer case. Of course engine coolant sensor is between alternator and AC compressor on top of engine. If a resistor sensor was subbed for a warning light switch, it may not work when needed....

 

The coolant is supposed to be changed every 36months or 45,000 miles, if not you could be looking at this.
Dexcool Pictures
Which means you need a new radiator.
If the temp sensor is covered in a layer of crud it will insulate the sensor and it will read cold.