Jump to content

2.5td temperature mysterys


Recommended Posts

Hi guys

I've got a strange issue with my temp guage where sometimes its fine sitting about halfway up, other times its absolutely nailed to the bottom of the red and stays there where as sometimes it will suddenly drop back down to normal instantly, not a slow creep back down.

Not using water as I've monitered it for a while. All I will say is it is now spending more time at the top of the guage than it is reading normal.

Also heaters and everything are as warm as always which leads me away from anything actually overheating but I'll let yous be the judge of that.

Cheers

Link to comment
Share on other sites

The "dropping back down to normal instantly" is the correct thermorstat behaviour - when it hits the right temp it opens and the temp drops. The "creeping" is when it doesn't properly open, the gauge then appears tardy and the temp stays high as not enough coolant flow is happening. (but of course the temp sender might be duff, but the thermostat is a cheap first fix).

Link to comment
Share on other sites

The Diesel Turbo, 200Tdi, 300Tdi and Td5 are all 2.5 turbo diesels (TD)...?

distinct differences, that's why the nomencalture is different but yes they are all turbocharged diesel engines.

Turbo diesel - indirect injection

Tdi - direct injection

Td5 - unit injectors no seperate injection pump

Link to comment
Share on other sites

No worries just making it clear ;) the 19j temperature sender is located at the back of the engine on the cylinder head, I'd argue making it a lot less sensitive to weird thermostat behaviour... I'd be looking at the electrical side of things, get it up to temperature, then go behind the dash and start wiggling some wires...

Link to comment
Share on other sites

Sounds like a short circuit on the green wire between the gauge and the sender unit - the sender is actually and earth, the wire earths the gauge through the sender unit, the resistance of which decreases with increasing temperature, no resistance giving full temperature indication. A short in the wire will bypass the sender and send the indication up, so a chafed wire with intermittent contact will lead to over-reading.

Link to comment
Share on other sites

Sounds like a short circuit on the green wire between the gauge and the sender unit - the sender is actually and earth, the wire earths the gauge through the sender unit, the resistance of which decreases with increasing temperature, no resistance giving full temperature indication. A short in the wire will bypass the sender and send the indication up, so a chafed wire with intermittent contact will lead to over-reading.

May I have a minor thread hijack to ask - do all the senders - oil pressure, oil temp, water etc work on the same principle as described above? With the wire-to-gauge going to earth through the sender, with the resistence varying according to temp?

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...

Important Information

We use cookies to ensure you get the best experience. By using our website you agree to our Cookie Policy