Gauge only shows heat when car is not moving, air from blowers only warm. Plenty of water. I'm guessing thermostat. Should I be getting a new housing and sensor with it, or can I just replace the stat? Can anyone suggest a supplier near Hereford? Thanks.

Gauge only shows heat when car is not moving.

What do you mean?? Let's say you drive, the engine is warm, you have no temp gauge indication, but if you stop at a redlight (car is not moving) the gauge needle suddenly jumps to 90C??

air from blowers only warm.

See this topic.

Should I be getting a new housing and sensor with it, or can I just replace the stat? .

Definitely buy housing with thermostat.

Edited 13 January, 201511 yr by RicardoM

Can you even buy a thermostat without the housing? When I did it, it was cheap to replace the whole lot, and the bit that had broken off was actually part of the housing anyway so nothing else would have solved the problem. I understand this is common.

The temp rises very slowly if the car is stationary and running, and the blowers produce nice hot air, but the gauge drops back to zero after a few hundred yards of normal driving.

 

I bought a thermostat for £12, it "should" be right, but I'm worried now that the problems mentioned above might manifest.

 

Wanted to ask if it's really necessary to drain the whole system though. Presumably it's a lot simpler to just disconnect a hose quite high up?

 

Thanks,

The temp rises very slowly if the car is stationary and running, and the blowers produce nice hot air, but the gauge drops back to zero after a few hundred yards of normal driving

Well... that's totally different from "Gauge only shows heat when car is not moving". You need to change the thermostat AND the coolant temperature sender. You need to drain only 1.5-2 liters of coolant to change the thermostat. Third party thermostats vary slightly in diameter and height (usually smaller than original) and you might end up with with a thermostat that does not open fully and overheating.

Thanks for the advice. I read about someone changing a thermostat and it was a little small so he used some silicone to make sure it was sealed. That's my plan B. I'm hoping ordinary general purpose silicone will suffice.

 

Can you tell me why you think I need a sensor too?

 

Thanks.

Can you tell me why you think I need a sensor too?

Let's analyze your previous post. I quoted it below and emphasized the interesting part.

So you have a sluggish temp gauge while standing and a dying temp gauge when driving. I presume this problem is recent and not from previous owner 3 years ago.

The temp sensor has 2 thermistors inside. They change resistance with temperature. One thermistor helps ECU know the temp of the coolant and decide if the engine reached operating temp or not and act accordingly. If this thermistor failed you would've known it in the form of rough running, hard cranking, engine stalling, high fuel consumption, etc.

The other thermistor feeds the temp gauge directly, literally one black wire goes to a connector behind charcoal canister then directly to pin 2 of the white connector of the PCB that holds the cluster of instruments. If this thermistor fails, it can give weird readings on temp gauge.

Given the fact you said you have plenty hot air from blower, that means the coolant got at 90C yet the gauge indication was bad.

Temp sensors are well known for failing, that is why it is my first guess. Given your limited mechanics skills and tools, it is easier to replace it. Of course, the correct path would be to check the connector in between, the PCB for cold joints, and the temp gauge itself. If you feel confident, do it that way.

The temp rises very slowly if the car is stationary and running, and the blowers produce nice hot air, but the gauge drops back to zero after a few hundred yards of normal driving.

Edited 14 January, 201511 yr by RicardoM

Hey Ricardo, I really appreciate your feedback and value your expertise.

The problem is only recent - in the last week I think. Before that, the temp gauge showed a very steady constant 90 after warming up, but would rise higher after some parking practice with my learner daughter, or sitting in slow traffic. Fan would cut in eventually.

 

My understanding is that the thermostat is stuck open, so the water doesn't get properly hot before going to the radiator/heater matrix.

If the car isn't moving, there's no cooling from the radiator so the water temp continues to rise (as indicated by slowly rising gauge). Air from the blowers also gets increasingly warm.

As I drive, the radiator cools the water, so the gauge drops, as does the blower air temp.

I can't see any odd gauge behaviour in this, though it would seem odd (to me, no expert) that the temp sensor AND the thermostat would have both failed at the same time.

 

If I have been ambiguous in my descriptions of the issues I apologise - I try to keep it brief and pertinent, but I guess I should have been more accurate and wordy with my post.

 

Thanks again for all your help.

If I have been ambiguous in my descriptions of the issues I apologise - I try to keep it brief and pertinent, but I guess I should have been more accurate and wordy with my post.

No problem. We all get confused sometimes. Keep us updated with your findings. If you can, take photos as you remove the old thermostat. A comparative photo with old/new thermostats would be helpful too, as we all change it quite often.

Edited 15 January, 201511 yr by RicardoM

Oh dear.

 

Got the old one out, its the housing that's broken so the plunger can't stay in.

Will post photos but not sure how to atm.

I guess I now have to refit the housing without the stat so I can pick up the kids and get a new one from town. That will be ok won't it?

Thanks

I guess I now have to refit the housing without the stat so I can pick up the kids and get a new one from town. That will be ok won't it?

Thanks

Yeah... It will take longer to warm up the engine, but for a day it's Ok.

Ok here's some photos.

First - the broken thermostat as I removed the cover.

You can see fracturing on the other side too.

 

The plunger came out when I put it in boiling water so I decided to try and fix it, probably temporarily.

 

I drilled a couple of holes into the housing and bent up some 2mm stainless wire to substitute the broken plastic bit.

 

The O ring was squashed quite flat, so I cut an O ring packer from neoprene to go under the O ring.

 

Put it together and fitted it back onto the car.

 

 

Seems to work - the gauge got to about 85 degrees then the thermostat opened and the radiator hose started to get hot.

 

Thanks for all your help. I'm sure I'll be back soon!

 

 

 

Ok, a very short lived repair.

After the first test drive, all was well, but later, after cooling a bit, the gauge was staying low.

Just wanted to ask if the plunger pin would normally retract on it's own (ie without the spring) as it cools? Or does the thermostat rely on the spring to retract the plunger pin?

Thanks for any replies.

Or does the thermostat rely on the spring to retract the plunger pin?

Yes. Otherwise the spring would be redundant, wouldn't it?

I didn't test the cooling and retraction with the spring in - I just pushed it back in manually as it cooled, and it did seem suprisingly stiff....

 

I'm guessing my plunger pin is very stiff in the open position, and the spring isn't strong enough to push it back.

But that would be a bit of a coincidence with the plastic housing breaking at the same time, so I'm not sure.

 

Anyhow, new genuine part including the sensor section now ordered, so hopefully I'll get it all sorted this weekend....