Engine: D5: Volvo V70 D5 185bhp 2006 Mystery Coolant Leak

[Clan]

Originally Posted by TurboDiesel2006

Do you know which pin(s) on the ECU go to the coolant temp sensor?

As a matter of fact yes ...

Both in the plug which goes to the engine not the plug which goes to the body ..

Pin 60 Grey with Red stripe
Pin 56 Brown with Black stripe ...

[cheshired5]

Originally Posted by TurboDiesel2006

Vida tells me the error code is ECM-2000 Engine Coolant Temperature Sensor Signal to Low. Something in the back of my mind says if the MAF sensor is faulty it will give these symptoms.

If you click on a fault code, Vida will give you the explanation for the code and the possible causes and fixes.
For ECM-2000, a faulty MAF sensor will not be one of those causes and you can confirm MAF operation using live data then compare to the range stated in Vida.
My bet is that your ECT sensor plug live is shorted to ground somewhere.
Multimeter on DC Volts, one probe on battery + terminal or any permanent live, other probe check each of the ECT plug terminals with ignition on.
Only one plug contact should give battery voltage (that's your ground) and the other should be the 5V (it won't read 5V in this scenario).
If both plug terminals read battery voltage, one of the terminals is shorting to ground so trace the wiring.

Originally Posted by TurboDiesel2006

I checked it with a multimeter.
With the engine cold and ignition on I am getting 3.35 kOhms resistance across the terminals. Is this withing range?

You have Vida which contains the range of resistances in the Component Specifications section of the Product Specifications section within Information.

If you have Vida, the best advice I can give is to learn how to use Vida as that's where nearly everyone's answers come from anyway.

[TurboDiesel2006]

The voltage between ECU pins 56 and 60 is +4.9V

A continuity check on each cable from the ECU connector pins 56 & 60 to the Coolant Temperature Sender plug was successful i.e.no breaks in the cables.

I rechecked the voltage at the sensor plug and this time it read 4.9V.

The Coolant sensor resistance was 3.29kOhms cold reducing to 460 ohms when warm but not yet hot. The fan stills runs full-time so it takes a while to warm up. From Clan's comment I think this is withing range but I am thinking of replacing the Coolant Sensor anyhow just to eliminate it from enquiries

The Coolant temperature data stream is fluctuating between 56 deg C and 147 dec C causing the Overheating, Stop Engine message to appear. If I rev it to a constant 1500rpm to warm it up and test the sensor it doesn't run 100%smoothly, faltering occasionally for a moment then picking up.

I agree that the most likely thing is that I have missed a connector or dislodged something while replacing the hose (the car has never had any cooling issues in 10 years of ownership) but I have taken it apart and put it back twice now and I can't see anything untoward.

I will take it apart again and do the checks suggested by CheshireD5.

Thank you all for the advice, I am completely stumped on this.

[cheshired5]

My take on the latest post ^^^^^ is that there is currently no evidence of any fault with the ECT sensor itself and replacing it would be a waste of time and money.

Everything so far points towards a wiring issue between the ECT sensor plug and the ECM and all of my efforts would be in that area only.

[Clan]

Originally Posted by TurboDiesel2006

The voltage between ECU pins 56 and 60 is +4.9V

A continuity check on each cable from the ECU connector pins 56 & 60 to the Coolant Temperature Sender plug was successful i.e.no breaks in the cables.

I rechecked the voltage at the sensor plug and this time it read 4.9V.

The Coolant sensor resistance was 3.29kOhms cold reducing to 460 ohms when warm but not yet hot. The fan stills runs full-time so it takes a while to warm up. From Clan's comment I think this is withing range but I am thinking of replacing the Coolant Sensor anyhow just to eliminate it from enquiries

The Coolant temperature data stream is fluctuating between 56 deg C and 147 dec C causing the Overheating, Stop Engine message to appear. If I rev it to a constant 1500rpm to warm it up and test the sensor it doesn't run 100%smoothly, faltering occasionally for a moment then picking up.

I agree that the most likely thing is that I have missed a connector or dislodged something while replacing the hose (the car has never had any cooling issues in 10 years of ownership) but I have taken it apart and put it back twice now and I can't see anything untoward.

I will take it apart again and do the checks suggested by CheshireD5.

Thank you all for the advice, I am completely stumped on this.

You will probably find a rotted or damaged wire somewhere in the loom where you were working , especially as it came back to life when you disturbed it again . why not put your voltmeter across the semsor end and wiggle the loom where you were working and see if you can see where abouts the fault may be ... Bosch Temperature senors are rock solid even after 40 years , unlike Smiths :-)

[TurboDiesel2006]

I think I have sorted the fan coming on at full blast from start up with unstable temperature gauge. The problem candidates were the Coolant Temperature Sensor or a short in the wire between the Sensor connector and the ECM. All this started with the car loosing coolant and me then fitting a new pipe between the EGR Cooler and cylinder head.

I ran the engine and checked the resistance across the Coolant Temperature Sensor pins every 10 deg C from cold to normal (using a laser thermometer to measure the temp as the Vida read out was jumping around all over the place). I compared these against the full specification available on Vida which showed the sensor to be bang on spec.

Previously I had disconnected and reconnected the battery and the ECM immediately gave 5v across pins 56 & 60 and the Sensor connector pins were the same which was what I was looking for. But when I started the engine the Sensor connector was giving 0v and occasionally 3ish volts, the fan was constantly on full blast, Vida was showing the the coolant temperature to be fluctuating by 100 degC, the temperature gauge was all over the place and Overheating Stop Engine Message was on screen. This indicated Pin 60 wire was probably grounding between the ECM and Sensor but I tracked the loom and couldn't see any obvious problems or signs of wear. A continuity check confirmed the wires wires were not broken.

So I went back to Vida and cleared all the error codes which I had not done before as I had assumed they would clear automatically. I then disconnected the battery and left it for a couple of minutes, a bit like a Microsoft alt/ctrl/del reset. I then reconnected everything and started the car. Hey presto the fan didn't come on, the temperature gauge was stable and Vida said the coolant temperature was warming up nicely. I have now done two test drives and all appears ok.

So it seems the important thing was to clear all the error codes in Vida and do the equivalent of a reset. This implies that somehow the ECM had somehow gone into an undefined state from the original low coolant message and was giving incorrect voltages to the temp sensor. I can't explain this. To repair the split pipe I had disconnected the battery and ECM and removed all the MAF to turbo pipework then when I re-connected it all I had more problems that when I started.

Thank you to everybody who replied and gave me advice particularly Clan and Cheshire5.

If this fix is not stable and the problem re-appears when I do a longer run I will update this post.

For future reference the Coolant Temperature Sensor resistances are:
Coolant 0 degC - 5.74 kOhms
Coolant 10 degC - 3.7 kOhms
Coolant 20 degC - 2.45 kOhms
Coolant 30 degC - 1.66 kOhms
Coolant 40 degC - 1.15 kOhms
Coolant 50 degC - 811 Ohms
Coolant 60 degC - 584 Ohms
Coolant 70 degC - 428 Ohms
Coolant 80 degC - 318 Ohms

Car: Volvo V70 D5 SE 185bhp Manual Engine D5244/T4

[XC Viking]

H[I], I had the Same issue with my 2008 XC 90 D5. A minor leak that grew over many months. We found it to be an aluminium connector in the turbo cooler line. You can only just see it if you remove the base cover and look UP between the engine and firewall, with the engine running. Very hard for the average guy to get too. Hint:You can source a replacement from the wreckers, a lot cheaper than new. See the photo showing where the bit wears, it is hidden by the mount whilst installed. Trying to upload a photo but this software is pathetic. There is an aluminium U tube that the hoses attached to. The side that wears is opposite to the direction of the connected hose. Hope that makes sense, will continue trying to upload photos of the piece. Cheers. Ed.

[TurboDiesel2006]

I have now done several trips in the car and the constant fan problem, fluctuating temperature gauge and overheating messages have not re-appeared so touch wood resetting the ECM codes did the trick.

For completeness and to help anybody else who experiences the same problem I thought I would post a picture of the hose that caused the coolant loss and subsequent problems. It is the small 90 deg elbow hose connecting the EGR Cooler to the cylinder head. It was split adjacent the hose clip as shown in the attached picture. I identified it after pressurising the system and then listening for the hiss. I accessed it by removing the ECM and adjacent hoses down to the turbo and removed the factory one-use clip using a couple of electrical screwdrivers to prise the locking tabs apart.

At the time the official Volvo replacement was going to take some days to arrive so instead I bought a 16mm (5/8") ID EPDM Rubber polyester cord reinforced heater hose (£9.50) via ebay that arrived next morning (picture attached). I had to cut this down to size which I did in stages so that it didn't foul the turbo pipe. I pressure tested the system to 2 bar with it in place and so far (again touch wood) all is ok.

[qazxsw123]

Originally Posted by TurboDiesel2006

I have now done several trips in the car and the constant fan problem, fluctuating temperature gauge and overheating messages have not re-appeared so touch wood resetting the ECM codes did the trick.

For completeness and to help anybody else who experiences the same problem I thought I would post a picture of the hose that caused the coolant loss and subsequent problems. It is the small 90 deg elbow hose connecting the EGR Cooler to the cylinder head. It was split adjacent the hose clip as shown in the attached picture. I identified it after pressurising the system and then listening for the hiss. I accessed it by removing the ECM and adjacent hoses down to the turbo and removed the factory one-use clip using a couple of electrical screwdrivers to prise the locking tabs apart.

At the time the official Volvo replacement was going to take some days to arrive so instead I bought a 16mm (5/8") ID EPDM Rubber polyester cord reinforced heater hose (£9.50) via ebay that arrived next morning (picture attached). I had to cut this down to size which I did in stages so that it didn't foul the turbo pipe. I pressure tested the system to 2 bar with it in place and so far (again touch wood) all is ok.

Great info thanks. This was a great help in locating and fixing the same issue on my 2005 XC70 D5 185.

I replaced the badly perished and mis-shapen leaky hose with an oem part for about £25, and used jubilee clips to secure it. It was actually less fiddly and a quicker job than I anticipated, and I had no problems with error codes, etc.

It's been fine now for several weeks / 1,000 miles.