98 S70 Overheats while idling

[harryhendo]

Great. So the next thing I'd suspect is some blockage in the system, or a water pump that is not efficiently cycling coolant.

Do you know when the cooling pump was last replaced? It is usually done when the timing belt is replaced, since it is run off the timing belt. It has a "weep hole" that leaks coolant when the seals start to fail. Any evidence of coolant below the engine after being parked overnight?

For blockage, you can drain the block of coolant by opening a drain plug in the block. On my '00 S70, I removed the plug and the thermostat and put a garden hose in the thermostat area (when the engine is cool!) to flush the block. You can then put the garden hose in the top radiator hose, open the radiator's drain, and backflush the radiator.

[scot850]

harry is making a good point also. The thermostat. The dealer foreman I know reckons 2-3 years for a thermostat to be safe. Sure they can last a whole lot longer than that, but when they go....! So if you do the thermostat, then it is definitely worth doing the ECT as it is right under the thermostat.

Neil.

[shaker_chi]

Sorry, I'm a bit confused. When I grounded the relay the fan did NOT turn on. The fan does work when I connect it directly to a power source though. If the fan does not turn on when I ground the relay, I assume that would indicate a bad relay. No?

[bmdubya1198]

If the fan is not working when connected to the relay, I would think the relay is bad. Clearly the fan is fine if it works when you connect it straight to a power source.

[esl_97_850_T5]

There is another way to check the radiator fan -- command the Motronic 4.4 to test the engine cooling fan.

With a KWPD3B0-conversant ELM327 v1.5 USB cable and the Motronic 4.4 (ECM that's usually on a 98 S70/V70), you can perform an "Engine cooling fan, high speed" test as follows. First do the setup:

Code: Select all

ATZ
ATL1
ATE1
ATI
ATSP 3
ATDP
ATH1
ATAL
ATKW0
ATTA 13
ATRA 13
ATIIA 7A
ATWM 82 7A 13 A1

then issue:

Code: Select all

ATSH 85 7A 13
B0 1F 3203

then listen for the fan cycling on and off every 3 seconds. It lasted 18 seconds on my car. But it may take longer on your car, since the OTP Volvo 850 Repair DVD says it takes 30 seconds.

Then you can perform an "Engine cooling fan, 1/2 speed" test (by issuing only one more command since you're already connected to the M44, and you've already issued the proper ATSH command):

Code: Select all

B0 0E 3203

[I'm presuming those two ECU 7A destined B0 commands (B01F 3203 and B00E 3203) test: the M44, the fan relay, and the fan, but someone more knowledgable with the M44 schematics will have to verify that. I don't want to spend the time to look at the schematics.]

The results of those commands above should look something like the following, where the first 5-6 lines will likely appear to overwrite each other:

Code: Select all

>ATZ
ELM327 v1.5

>ATL1
OK

>ATE1
OK

>ATI
ELM327 v1.5

>ATSP 3
OK

>ATDP
ISO 9141-2

>ATH1
OK

>ATAL
OK

>ATKW0
OK

>ATTA 13
OK

>ATRA 13
OK

>ATIIA 7A
OK

>ATWM 82 7A 13 A1
OK

---- Make sure this starts off with 85, not 84 or 83.
>ATSH 85 7A 13
OK

---- Here's the Engine cooling fan, high speed test.
>B0 1F 3203
BUS INIT: ...OK
83 13 7A F0 1F 1F 

  - For 18 seconds, the fan operates as follows:
        * 3 seconds on, 3 seconds off, 
        * repeat that 6-second cycle 3 times for 18 seconds total.

---- Here's the Engine cooling fan, 1/2 speed test.
>B0 0E 3203
83 13 7A F0 0E 0E 

  - It used the same "3 sec on, 3 sec off, repeat 6-sec cycle 3 times for 18 sec total" timing.
  - It was not as loud as the full speed test.

This mechanism should work with any KWPD3B0-conversant ELM327 device.

An easy way to get the initial setup done (ie, all commands from the ATZ thru the ATWM command) is to use volvo850diag, click "Start Realterm", then click ECU 7A "Setup". If you get that far, it would probably be a good idea to go ahead and test the connection by pressing either ECU 7A "ATSI" or "Read DTCs".

At that point, you can then click in the Realterm Terminal pane to establish focus in that Terminal pane, then type the 3 commands:

Code: Select all

ATSH 85 7A 13
B0 1F 3203
B0 0E 3203

esl_97_850_T5

[shaker_chi]

Thanks ESL. Great info!!! I used to be able to do that with my 94 850 with just the punch of a button. I replaced the relay and now I am up and running. Thank you everyone for all the responses. Very helpful indeed!!!!