1998 V70R AWD - No over-run on engine cooling fan.

Pentacyl · Post by **Pentacyl** » 19 Feb 2021, 09:58

Any ideas why the engine cooling fan fails to run-on when the hot engine is turned off? Coolant blows out of the reservoir cap (New cap 10K miles).

The relay above the radiator/intercooler sandwich, checks out OK.

Is the run-on feature controlled by the costly, ECT sensor, below the coolant thermostat? Are there any routines to check out the sensor operation?

Hope someone can assist. Stay calm in these crazy CoVid times.

Post by **Chuck W** » 19 Feb 2021, 10:04

The fan run-on is usually the sign of a bad ECT sensor.

The coolant forcing its way past the reservoir cap isn't normal, and shows potential of pressurization of the cooling system, perhaps via a bad headgasket. That or some other blockage in the system (bad radiator, bad thermostat, etc).

By "hot" engine, do you mean over-heating, or just normal operating temps?

Pentacyl · Post by **Pentacyl** » 19 Feb 2021, 11:10

Hallo and thank you, Chuck W!

Sorry for delayed reply, had a wash machine engineer arrive. By "hot" engine, I do mean one at normal operating temp, 3pm mark on gauge.

The coolant back-pressure, though, was abit of a red herring. Sorry. This all started just before a forced, full engine rebuild, due to a dropped valve seat at only 182K miles. A previous owner must have been a thug...!

So, there shouldn't be any back-pressure - it's got a new, Volvo rad, pump et al, too. The fan however, still doesn't run-on. The car's not fully back on the road but the coolant hasn't spewed out of the reservoir, after test runs.

Before I spend a further ± $65.00 on a new ECT, do you know of any test for the existing unit, pls?

Post by **Chuck W** » 19 Feb 2021, 11:50

Oh, sorry, I misread. The fan *shouldn't* run after the engine is shut off. At least not normally. The only time that it does is usually when the ECT had failed, or is out of spec.

I'm confused. Does coolant spew out of the reservoir, or not?

Post by **scot850** » 19 Feb 2021, 16:29

Maybe there is a difference between the 98 and 99-00 models in how the fan operates. My 2000 V70R the fan is designed to run on based on the under hood temps. Only does it when it is really warm.

Neil

Post by **Chuck W** » 19 Feb 2021, 17:45

I'm running 98MY ECUs in both of our '97's and the fan shuts off every time we turn the cars off. The only time I recall them running after the car has been shut down was when the ECT sensor died.

Post by **abscate** » 19 Feb 2021, 20:12

ME7 on 1999- does run differently. There are several conditions which will give after-run on the cooling fan