Cooling system help part deux !!

Gmac · 02-02-17, 02:17 PM

Afternoon folks!

I've got myself some supplies!

Quick overview of the current situation...

Point 1. I reckon my temp gauge isn't showing the correct temp. So this may be the temp sender.

Point 2. There is a leak from the flange holding the temp sender above, which is going to need changing out.

Point 3. I think the temp sensor in the radiator isn't working correctly as my fans aren't coming on when the car is getting hot, ie over 95 degrees.

So.. I'm trying to decide what the best order to do things in are... I'd like to change the sender to the gauge first perhaps to see if that has any effect on the instrument cluster reading, will I lose a lot of coolant when taking this off to change?

I'm needing to change the flange too, but again not too sure if I should change this first, and how much fluid is going to be lost? (I don't have endless amounts of coolant, enough for a fluid change)

Same goes for the radiator sensor really, can it be changed out without losing too much fluid? I'd like to change sensors using the old fluid so as not to waste new fluid. Ie by doing a whole fluid change first.

I do have another thermostat to change out too.

Any hints and tips welcome before a just give things a go would be great!

John. · 02-02-17, 03:39 PM

Am I right in saying you've changed the thermostat?..yes?
I'd be for dumping all the coolant out , filling with water and flushing out the old coolant and then fit all the new bits and add the fresh anti-freeze.

Don't suppose you'd loose much coolant if you just changed the sender unit though, just be ready for a quick swap

Gmac · 02-02-17, 04:42 PM

Quote:

Originally Posted by John.

Am I right in saying you've changed the thermostat?..yes?
I'd be for dumping all the coolant out , filling with water and flushing out the old coolant and then fit all the new bits and add the fresh anti-freeze.

Don't suppose you'd loose much coolant if you just changed the sender unit though, just be ready for a quick swap

Not changed the thermostat yet. Needed to get the above tub of coolant.

Never crossed my mind to use water to flush out the old stuff! Se yeh not much to lose if i just change out the sender at the moment.

Cynical26 · 02-02-17, 08:08 PM

Gmac, I'm doing some of the same things as you. Waiting on my new temp sender unit to arrive. I'm going to change that first and then top up the coolant, see if that gets my temp gauge working and turns off the flashing temp warning light on my dash.

I'm going to do that first as I'll only loose the coolant head above the sender. If that doesn't sort the temp gauge issue (can't see that it's showing the correct temp of 70 degrees all the time) I'll do the thermostat.

TBH I'm hoping not to have to change that as it loose like it's never been out, worried about snapping the bolts on the inlet.

I don't think you'll loose too much fluid until you're changing the radiator sensor, that's at the lowest point on the coupe. Remember to replace the seal on that when it's out.

Interested to hear how you get on. Good luck

Gmac · 02-02-17, 08:30 PM

Yeh, definately going through the same scenario.... Well I'm hoping to get at mine tomorrow. I'll take phots and keep this thread up to date!

I think at the moment my plan is to change the temp sender on the flange, to see if that sorts out the temp gauge on the cluster. If that's worked, I'll then change the flange, as it's leaking. I'll then change the radiator temp sensor on the radiator, as the fans aren't kicking in when the car gets hot.

After that, I'll assess as to what's next..

Cynical26 · 02-02-17, 08:47 PM

Quote:

Originally Posted by Gmac

I think at the moment my plan is to change the temp sender on the flange, to see if that sorts out the temp gauge on the cluster. If that's worked, I'll then change the flange, as it's leaking.

Why are you not changing the flange and temp sender at the same time? You'll loose he same amount of fluid each time. Or you could loose half the amount by changing them once?

If you're going to do them both anyway, and if there's no other reason not to, I'd do them at the same time. Filling the fluid in mine is a pain in the ass and I'd like to do it as little as possible!

Gmac · 02-02-17, 09:31 PM

Quote:

Originally Posted by Cynical26

Why are you not changing the flange and temp sender at the same time? You'll loose he same amount of fluid each time. Or you could loose half the amount by changing them once?

If you're going to do them both anyway, and if there's no other reason not to, I'd do them at the same time. Filling the fluid in mine is a pain in the ass and I'd like to do it as little as possible!

Open to suggestions, so yeh, sounds like that's what I should do. I suppose I thought I'd lose a lot less changing out just the sender. Every day is a school day!

Davids · 03-02-17, 09:11 AM

Hi
You chaps have probably seen this but I could have done with it a few weeks ago when I did a coolant, thermostat change, that lead to the aux rad being re-cored.
http://20v.org/coolanttutorial.htm

The photos are helpful, especially like me if you have to put it all back together a few weeks later.

Cheers

David

vorsprung durch technik · 03-02-17, 09:16 AM

Quote:

Originally Posted by Davids

Hi
You chaps have probably seen this but I could have done with it a few weeks ago when I did a coolant, thermostat change, that lead to the aux rad being re-cored.
http://20v.org/coolanttutorial.htm

The photos are helpful, especially like me if you have to put it all back together a few weeks later.

Cheers

David

Excellent 20v link David!

Gmac · 03-02-17, 08:24 PM

Quick update... replaced the two senders in the flange, and the flange itself, you don't lose very much fluid at all. Probably helped that i unscrewed the header tanks and lowered it down in the engine bay. Started the car and helped it get up to temperature. A slight tweak on the 10mm nuts on the flange to stop a tiny leak from the bottom. No leaks from where it was leaking before! Got the car up to just shy of 110 degrees, and then shut it off. During this the fans never came on. Slight pause and with the keys out of the ignition, the afterrun fans started up! Woohoo, so that relay 272, has done the job! One job sorted.

I then topped up the fluid and took it out for a test drive, went for a bout a 20 minute drive, mixture of A and B roads, and the car never went above approx 78 degrees. So something not right here. I then changed the temp sensor in the bottom corner of the radiator, straight forward job, and then tackled the thermostat. Boy, that's a bit of a pig to get out!! Eventually worked out how to get the upper left 10mm bolt off the flange covering the thermostat, still not easy though! So I've changed that and got it back together. Not refilled the fluid yet though. I'll maybe pop out to the garage now and fill up the system. So tomorrow, take it for another run to see if changing out the thermostat has done anything to the temp reading on the cluster, and also to see if when it gets hot and the car is running, the fans kick in, with the new temp sensor in place. Also check for leaks from the flange covering the thermostat, as it was a ball ache to re tighten the top left bolt!

Progress has been made. A little unsure as to why the temp gauge isn't showing a normal 90 degress though!! Any thoughts?

02-02-17, 08:30 PM	#5
Gmac Grown up member Classic Audi Club Member Join Date: Feb 2015 Location: Aberdeenshire Posts: 686	Yeh, definately going through the same scenario.... Well I'm hoping to get at mine tomorrow. I'll take phots and keep this thread up to date! I think at the moment my plan is to change the temp sender on the flange, to see if that sorts out the temp gauge on the cluster. If that's worked, I'll then change the flange, as it's leaking. I'll then change the radiator temp sensor on the radiator, as the fans aren't kicking in when the car gets hot. After that, I'll assess as to what's next.. Last edited by Gmac; 02-02-17 at 08:34 PM.

02-02-17, 03:39 PM	#2
John. 4 ring whore! Classic Audi Club Member Join Date: Mar 2011 Location: Scottish Borders. Posts: 7,520	Am I right in saying you've changed the thermostat?..yes? I'd be for dumping all the coolant out , filling with water and flushing out the old coolant and then fit all the new bits and add the fresh anti-freeze. Don't suppose you'd loose much coolant if you just changed the sender unit though, just be ready for a quick swap

02-02-17, 08:08 PM	#4
Cynical26 Grown up member Join Date: Dec 2016 Location: North Ayrshire Posts: 735	Gmac, I'm doing some of the same things as you. Waiting on my new temp sender unit to arrive. I'm going to change that first and then top up the coolant, see if that gets my temp gauge working and turns off the flashing temp warning light on my dash. I'm going to do that first as I'll only loose the coolant head above the sender. If that doesn't sort the temp gauge issue (can't see that it's showing the correct temp of 70 degrees all the time) I'll do the thermostat. TBH I'm hoping not to have to change that as it loose like it's never been out, worried about snapping the bolts on the inlet. I don't think you'll loose too much fluid until you're changing the radiator sensor, that's at the lowest point on the coupe. Remember to replace the seal on that when it's out. Interested to hear how you get on. Good luck

03-02-17, 09:11 AM	#8
Davids 4 ring whore! Join Date: Jan 2017 Posts: 3,124	Hi You chaps have probably seen this but I could have done with it a few weeks ago when I did a coolant, thermostat change, that lead to the aux rad being re-cored. http://20v.org/coolanttutorial.htm The photos are helpful, especially like me if you have to put it all back together a few weeks later. Cheers David

03-02-17, 08:24 PM	#10
Gmac Grown up member Classic Audi Club Member Join Date: Feb 2015 Location: Aberdeenshire Posts: 686	Quick update... replaced the two senders in the flange, and the flange itself, you don't lose very much fluid at all. Probably helped that i unscrewed the header tanks and lowered it down in the engine bay. Started the car and helped it get up to temperature. A slight tweak on the 10mm nuts on the flange to stop a tiny leak from the bottom. No leaks from where it was leaking before! Got the car up to just shy of 110 degrees, and then shut it off. During this the fans never came on. Slight pause and with the keys out of the ignition, the afterrun fans started up! Woohoo, so that relay 272, has done the job! One job sorted. I then topped up the fluid and took it out for a test drive, went for a bout a 20 minute drive, mixture of A and B roads, and the car never went above approx 78 degrees. So something not right here. I then changed the temp sensor in the bottom corner of the radiator, straight forward job, and then tackled the thermostat. Boy, that's a bit of a pig to get out!! Eventually worked out how to get the upper left 10mm bolt off the flange covering the thermostat, still not easy though! So I've changed that and got it back together. Not refilled the fluid yet though. I'll maybe pop out to the garage now and fill up the system. So tomorrow, take it for another run to see if changing out the thermostat has done anything to the temp reading on the cluster, and also to see if when it gets hot and the car is running, the fans kick in, with the new temp sensor in place. Also check for leaks from the flange covering the thermostat, as it was a ball ache to re tighten the top left bolt! Progress has been made. A little unsure as to why the temp gauge isn't showing a normal 90 degress though!! Any thoughts?