The car is a 95 960 with 180K miles. It is my daughter's but I do the maintenance. We would both appreciate your help.

The whole truth is that I do get a B2 122 code but I understand that to be related to cruise control and an A1 code for the PN transimission switch but nothing else. I also get no ready from the A6 terminal and there appears to be no wire going to that point in the A block.

Sorry that the story is a bit long but it has me stumped.

For a couple months, there was regular coolant loss and dripping under the engine. I replaced the water pump a couple times and then discovered a bad thermostat o ring. Replaced that and car was good for 2 weeks then started reading toward hot after about 5 minutes. I was concerned that it was a head gasket. When getting hot there was a very small leak in the radiator and in the coolant overflow tank. The car did not go to the red.

I again thought that it might be a head gasket but I wanted to check everything else first. My first step was to replace the thermostat and test for excessive pressure in the coolant system. No problems and the car ran at the proper temperature. I drove it over 20 miles with lots of starts and stops. I was feeling very good and I assumed that was now fixed so I replaced the radiator and coolant tank. Refilled, tested, and all was good. I did not drive it very far after fitting the new radiator and overflow tank. Just enough to get to the correct temperature fill to the correct level.

Because I had forgotten the diagnostic code reset procedure and the check engine light was on, I just disconnected the battery and left it overnight. Next morning, reconnected and was going to move the car to the driveway. It would start but I had to use the gas pedal to keep it going and it would not idle. I could drive it if I kept RPMs to about 2000.

I pulled plugs and saw no problems like coolant in the cylinders and the car will run and even seems to hit on all cylinders at higher RPMs. Seems to miss several at low RPMs. There is no smoke of any type. I have done a visual check of vacuum lines and other connections.

I will be away from the car for a few and would like to use the time to get parts if anything seems appropriate or to plan the next step.

At this time, I am afraid that it is the head gasket and that last night was the first time that it sat for 12 hours with the system holding pressure as far as the radiator and coolant tank were concerned. The argument that I see against the idea is that it would run and I could drive it and the problem never went away. Wouldn't an overnight coolant problem have been burnt off after 10 minutes?

Thanks in advance.
Steve

 

I don't know if the coolant system has anything to do with it not running normally.

 

Thanks. I look forward to checking it out.
I first assumed that I had knocked a vacuum hose off or a connector, but see nothing wrong.
it would be a heck of a coincidence but weird things do happen.

 

Take a compression or leak down to confirm the head gasket diagnosis. HGs are tricky and confuse many: they separate coolant from oil from air (compression). Add to that various heat cycles and wear levels and you got quite a possibility for variables. Coolant in the oil is just one symptom, most commonly, but by a long shot not exclusive. I'd say, yes, the HG is a problem here but no need to speculate, take the test to make sure!

 

It took awhile to get to this point but all seems to be fine now.

When we last communicated, I had replaced a waterpump, thermostat and gasket, radiator, and overflow tank following coolant leaks and raising temperature when driving. After a day of the car running well, I disconnected the battery to reset the computer overnight. Next morning, I discovered that the car ran very badly. It would start but die after three or four seconds unless the pedal was judiciously pumped and applied.

Good news discoveries included the timing belt being spot on timing wise, good compression in all cylinders and no evidence of carbon monoxide in the coolant (used a CO tester in baggie sealed to coolant tank). My fear was a bad head gasket.

During diagnosis, I replaced one coil because it was sparking through the side and I put in new plugs while I was at it. No change in behavior. Fuel pressure was OK.

Having no better next steps, I started disconnecting sensors and fuel injection components. When I disconnected the MAF, all was suddenly good. I checked the archives and read that I could drive the car that way and I did for awhile but the car would die at idle when cold and did not run its best. I ordered and installed a new MAF yesterday and my daughter is back on the road.

The big question remains, why did the MAF die overnight? Or, was it running in some limp home mode and covering the bad MAF before being reset overnight. Maybe something happened when I sprayed down the engine bay a bit to clean away the coolant that had sprayed here and there and otherwise leaked during the radiator and coolant tank change. But, I don't see why that would have occurred.

As of now, the car is running very well. FCP Groton, Euro, had the best MAF price if you want to go with Bosch and I did want to buy Bosch. Of all the work that I did, the new waterpump and repeated water pump installs were the unnecessary effort. If you think that you might have a waterpump leak, replace the thermostat and thermostat seal first. It's easy and about $10. My seal was cracked and the leak looked like it was from the water pump.

I think that I could have avoided the temperature rise problem if I had replaced the thermostat at the same time. About two weeks after replacing the thermostat seal, the thermostat failed. The thermostat failure caused temperatures to rise and showed a leak in the radiator and coolant tank -- we did not allow temps to rise to the red.

Maybe both the radiator and the coolant overflow tank needed to be replaced but then maybe not. Of course, the car should now run another 70K now without incident.

 

Glad you got it figured out.

MAF's are electronic parts exposed to the elements. They are time bombs.

 

I am not a mechanic, just a long time Volvo owner and have made many observations over the years.

Very probably the water pumps were not issues. A leak at the t-stat housing would be more likely. Those pumps are well built and should go to 150 miles easily. The down side is if one fails it takes the timing belt with it, so for the extra money it is better to be cautious and replace well before any failure. Coolant leaks are sometimes hard to track down. Usual suspect in order of occurance, radiator upper hose neck cracks, oil cooler hoses, heater valve, coolant filler bottle cap or bottle. Any others will have to carefully inspected for a dried white powder substance. Very hard to do under the hood with all that dust and road salt.

With the OBDi diagnostics, the electrical connections are weather resistant at best. sometimes just the act of unplugging and replugging a sensor is enough to bring it back in line, I imagine that some water worked its was into the connector and caused problems. Many of the sensors use so little voltage that contact oxidation only has to be slight for interference with the engine management. But, I think the car has a great limp home mode when needed. The only sensors needed to get home are, RPM and throttle position.

I don't think Volvo has a good approach to water tight or non oxidizing connectors. I remember thinking with all of Volvo's earth friendly approaches to car building, my old 240 suddenly had idling issues, I opened the hood and most of the wiring insulation any where near the engine was missing. They perfected the worlds first biodegradable wire insulation. The car was about 6 years old at the time.

Do you still have the old MAF, you should try plugging it in and see if it acts up. MAF's do fail but not that often.

DanR '94 964 388,000 (154,000 on the new engine) - 2008 S60 T5- 88,000

 

I did plug and unplug a couple times to confirm the diagnosis but I could have tried cleaning contacts and such. There was a $75 core charge and I put the old one in the mail the next day.
I absolutely agree about the thermostat leak. Very hard to locate. In fact, so hard that I would recommend that if you suspect a water pump leak that you replace the thermostat seal just in case -- $3.
At least this all will be there for the next person with similar problems.

 

Thermostat and WP are not that close. Best way to find coolant leaks is to check for them when you get home, don't turn off the car, keep it idling and look at the locations Dan noted and/or underneath, where coolant drops.

 

I had a thermostat seal leak on a 960 that I chased for 3 months. Lol The darn thing was pulling the coolant down and to the other side of the motor. I think I did find it with the car hot and idling in my garage.

What I don't understand is why you didn't have a CEL???

As for water pumps, I had to replace a leaking one at 86,000. It was 12 years old. So I try to replace them every 10 years no matter the mileage.

 

I could bother explaining how the leak can track behind the plastic shield and mask its origin but, if you don't want to just replace the $3 seal, one useful thing you can do is wedge white pieces of paper towel around the base of the thermostat housing. You will need needle nosed pliers. After a bit, pull them out and look for signs of coolant.