98 V70 non-turbo near overheat problem

Post by **98v70dad** » 18 Mar 2015, 16:57

Today on my 37 mile drive home I noticed that the engine coolant temperature gauge was just kissing the first red bar on the coolant temp. gauge. Today was the first hot day this spring at about 84 degrees. I was running the air conditioning. Traffic was very bad and had ground to a stop and go barely moving sort of thing. Once I noticed the high temp reading, I shut off the air conditioning and turned the heat on maximum. The temperature gauge dropped almost immediately a few notches on the gauge. When I got to a point where I was moving again (over about 20 mph) the gauge dropped to the 3 oclock position where always is. When I got home the radiator fan was running, the coolant level was at the maximum level where it is supposed to be.

I'm a little perplexed. I've never had a car get hot and then somehow recover. I never overheated but I got darn close. I expected the air over the radiator to lower the temp once I got free of the traffic gridlock but I also expected the temp to rise up again at the next stop light and it didn't happen. Also, gridlock happens every day including yesterday. It was about the same temp outside yesterday and the old difference is that today I had the AC on.

Actually too hot is overheating in my opinion, but I never got so hot that the fluid came out of the system as steam. I suspect that there's something wrong with the fan or a thermostat or relay that controls the fan. If anyone can provide some advice about what may be wrong I'd appreciate it

The car has 125,00 miles and it had the radiator, all the hoses,the heater core, the coolant thermostat, the coolant, etc all recently replaced. Heater core is about 2 years old and everything else is about 5 months old. All parts are Volvo except for the rubber. The temperature sensor was replaced about 3 years ago. The car is due a timing belt replacement at 140,000 miles. Water pump is original (I think). Radiator fan is original. Car had the PCV system overhauled about 3 months ago....all new stuff. Also, I have no codes on my odb ii reader.

Post by **misha** » 18 Mar 2015, 18:07

Themostat,ect or radiator fan relay.
Since thermostat and ect are new,i would inspect a relay.Check for wires going into it and all it's connections.Could be that connections are corroded.

Post by **98v70dad** » 18 Mar 2015, 18:19

misha wrote:Themostat,ect or radiator fan relay.
Since thermostat and ect are new,i would inspect a relay.Check for wires going into it and all it's connections.Could be that connections are corroded.

Thanks. Where do I find the fan relay?

Post by **kahl** » 18 Mar 2015, 20:40

They are above the fan slightly to the passenger side of car, under the plastic radiator shield. They slide out.

Post by **98v70dad** » 18 Mar 2015, 20:47

What does the fan relay do? Are there any other things to suspect? I found it by the way. Actually pretty easy to locate once you know where to look.

Post by **erikv11** » 18 Mar 2015, 23:27

Ozark Lee to the rescue:
https://www.matthewsvolvosite.com/forums ... =1&t=37188

The other things I can think of, misha covered: ECT, thermostat, possibly the fan itself.

Post by **E Showell** » 19 Mar 2015, 05:18

I had ECT issues a while back and was surprised at the amount of oxidation in the electrical connector. Just for the sake of investigating perhaps the simplest cause first, I'd consider unplugging the electrical connection for the ECT, shooting some contact cleaner in there and applying some dielectric grease to the connectors before re-attaching. It just might save you a whole lot of time and effort.

Post by **98v70dad** » 19 Mar 2015, 05:30

A dumb question maybe, but where do I find the ECT? I haven't had any issues with it to date so I've never gone looking for it. I've misplaced my haynes manual for the V70.

Post by **E Showell** » 19 Mar 2015, 05:46

It is squirreled away under the upper thermostat housing. Facing the radiator, trace the large diameter upper radiator hose on the left side of the radiator back to the thermostat housing. The upper thermostat housing is rounded and the ECT is the hex-headed fitting with the black wire coming out of it nestled to the right toward the lower edge of the curved thermostat housing. It can be obscured a bit by the upper radiator hose (which it can sit underneath of). Trace the black wire back to the connector, disconnect and check for oxidation.

No such thing as a dumb question on this board -- at least the members won't make you feel like it is a dumb question -- which is a large part of what separates this site from some others.

Post by **98v70dad** » 19 Mar 2015, 06:12

E Showell wrote:It is squirreled away under the upper thermostat housing. Facing the radiator, trace the large diameter upper radiator hose on the left side of the radiator back to the thermostat housing. The upper thermostat housing is rounded and the ECT is the hex-headed fitting with the black wire coming out of it nestled to the right toward the lower edge of the curved thermostat housing. It can be obscured a bit by the upper radiator hose (which it can sit underneath of). Trace the black wire back to the connector, disconnect and check for oxidation.

No such thing as a dumb question on this board -- at least the members won't make you feel like it is a dumb question -- which is a large part of what separates this site from some others.

After I asked the question I figured it out. I know where that is I just didn't know it was called an ECT. I replaced that about three years ago with what seemed like a good quality an aftermarket part. I don't suspect that its failed this soon and I didn't have any codes yesterday when I limped into the driveway. But it is possible that the connections are corroded. The joint at the thermostat housing seeped coolant for the first few weeks for some reason. It eventually stopped.

I reworked the PCV system AND the put in a new radiator several months ago so ALL of the electrical connections in that area have been disturbed or at least moved around. ALL of the wire harnesses had the protective plastic case crumbling so I replaced all of them ... this means touching and manipulating the wires. One of the connectors fell apart (cannon plug or two pulled out of the plastic holder) but I was able to push it back together and all seemed Ok. I don't remeber which connector this was.