I purchased a 1994 XJS convertible from Florida in July. I live in New Hampshire and I tried heater for first time. The temperature gauge does move a bit but I am not getting heat. I did have radiator system flushed and replaced when I got it a few months ago. Any thoughts? Could it be a thermostat? Or heater valve? There is no evidence of antifreeze leaks. Is this a pain to repair?

 

Welcome to the forums Rchuda,

I've copied this question from your Intro to XJS forum for advice from members with the same model.

Graham

 

I would replace the themostat, which is always important if the radiator is renewed. Then see if the heater valve that controls the water flow to the heater in the car is working. The theromstat is easy to get to and the water valve not difficult either.

 

Does your model have an auxiliary coolant pump? When the pump on my car ( 97 X300 4.0 six) failed, there was very little heat available. I replaced the brushes with some I picked up at an R.C. hobby shop. That fixed the problem.

 

I don't think he's got an aux cooling pump.

The only easy answer I can give you is to replace the heater control valve at the firewall. The OEM part is some crummy metallic looking thing, C41051, but I've read that an aftermarket plastic part works, and works better? I can't tell because I haven't installed it in my car, but I can tell you that I had to return the first C41051 because it was faulty. It was new, just not working. Plastic might be the way to go, search Four Seasons 74803. I believe I got this part number, or the idea, from Kirby and his Book. I want to make sure credit goes where credit is due.

 

Does anyone know what the correct temperature should be? I have found both 180 and 190 degree F thermostats available.

 

Rchuda,

It's part number EBC3621. That's an 88 degree C stat, so 190 degree Fahrenheit.

Cheers

Paul

 

I am going to try and troubleshoot. If I run the engine and warm it up and the antifreeze is not 190 degrees then the thermostat is probably faulty. If it gets to that temperature and still no heat then it is probably heater valve.

 

Do you have the means to read the temp setting using a cheap OBDIi plugin and a phone app? I'm guessing if you have a "US 1994" car, you can't do that? Or can you read the stat housing temp using an IR thermometer?

If the gauge isn't sitting about 1/2 way and you're getting no heat, I'd look at thermostat first. Also can you feel a sudden change in temp in the top hose as the stat opens? Its quite noticeable. Seems you could have a stat stuck open.

Cheers

Paul

 

The gauge moves only a bit off cold. I have only had the car since July and it came from Florida so I am sure heat was never an issue. I only just tried heat this weekend. I do not have a scan tool but I may try old school using a thermometer. Would it have thrown a code if engine was not at temperature?

 

In that case, sounds like you are on the right track with a thermostat swap. The only other suspect here is the coolant temperature sensor. A $20 part and a two minute swap. Quite frankly, I would do both, BUT if you're looking to save cash and spend time, perhaps you pull the sensor and clean it up. That could work, but for $20, on a part that is likely due for a change, I'd spend the money on the sure thing.

When resolved, you should notice better fuel economy too!

Don't rely on codes, these engines are notoriously frugal with codes. It's great when they finally decide to dole one out, but don't hold your breath.