I have a 96 960 that overheats under load on hot days. Houston, when on the freeways and over 70 mph......any hills or load the temp rises, and will go to red. Turn the AC off is no help. car just had a new radiator, fan and relay installed. Last week, a new thermostat. The coolong system was checked and I was told that the Water pump pressure was good. There is no water in the oil. One time when it over heated, I opened the hood to witness bubbles in the expansion tank, and a little leaking out. I have just ordered a new 1.5 bar expansion tank cap, and also an 87 Deg C thermostat. I understand the normal thermostat is 90 C. This will cool me off a few degrees without doing anything that will warp heads, or hurt running temp?? This is really frustrating, it only happens when I load the engine on a hot day going fast.....
Is the radiator designed by the engineers for cooler weather? I am an engineer myself, and don't see Volvo design engineers not allowing for proper capacity in the radiator, but you never know........If my head gasket was gone, I would see it in the oil, right? The last thing I can think of is that the resivoir cap was leaking and the cooling system pressure was down from where it should be at 1.5 bar??

Any help please...........the car is great. only 58K miles on this old beauty

 

Something's wrong. There is plenty of cooling capacity for these motors. I am not sure how people checked water pump pressure. This is a regular belt-driven vane pump, and it pumps at max capacity at about 2800 rpm. If you hear "marbles" shaking inside a can -- then yes, pump is cavitating, and it is about to explode. I don't think you would miss that.

You mention that there is no water in the oil. More importantly, do you see any oil bubbling up on the coolant reservoir?

I would also check that the thermostat is installed correctly. I would take it out (for now in the summer) and see if overheating occurs.

I hope you are not running the engine on the redline.

 

Thank you so much for the post!!!

I once had it approach the red line, but stopped and let it cool before heading home.

I can take the thermostat out to see if it would be the cure. Funny, I just had it replaced though. I have also ordered am 87C thermostat, as it seems to me that the standard is 90C. i am in Houston, and it is really hot here.

 

Hi Andy and welcome to the site.

A lower temp thermostat wont help. When that needle leaves the normal line at 3 O'clock and heads north, you're above 220 degrees (above 104c). So the t-stat is all the way open already.

Are you sure the fan is working? When the car gets to normal temp or when you turn the ac on, make sure the fan is turning.

I just pulled the head off of our S70 because of a similar situation. Breach in the head gasket above the cylinder but not enough to let oil through.

https://volvoforums.com/forum/volvo-...roblems-63516/

I'm reaching far here but if you're leak is near the temp sensor it could cause you to get heated readings.

 

Rspi is correct. Those few degrees of Temp difference in thermostats is not going to help you with overheating IMHO.

 

Wow....this could be true, but it really is hot instead of just indicatring hot.....I sure hope I have not done anything to the head. I never ran it in red line, but it approached and touched it once......

I have a bew cap coming, if it doesnt do it, I will prob replace the tank to be sure it doesnt leak or have a disformed inlet so the cap doesnt seat properly

 

I really do appreciate the help. I agree with you guys on the cap issue. Isnt it true that if I loose system pressure under load that the vapor pressure allows flashing/boiling and loss of heat transfer coefficient, hence overheat?

Hope the new cap does it, if not I am afraid that it is a head gasket that is weak under load only, and leaks?

I don;t lose coolant that I notice, b ut will keep an eagle eye on it....

 

Henry

I did get a new cap, replaced it, drove it a mile or so, and immediately the low coolant indicator flashed on. It was only a quart or so low, and after adding a little water drove it with no problem going slow. Still haven't loaded it..................but want to ask a question........

The need for a little coolant with a new cap makes me feel that the last cap did leak pressure, and that there was maybe a little trapped gas somewhere in the system. I don't see how any gas could be trapped, but on the other hand the new cap caused a small drop in coolant level. I drove it enough to see that the level stayed up to the max line, and made me feel that the head gasket was OK.........but I still need to load it up on the highway in the heat to see if we are fixed...........

Any suggestion why replacing the cap yields a small drop in coolant level, other than a leaky head gasket........or connection elsewhere?

Thanks in advance.......I really appreciate the kindness on the site.
Ragards
Ross

 

Coolant is pressurized inside this closed system. When there is an air-leak (e.g. a leaky cap) coolant will flow /expand towards lower pressure (e.g. Reservoir) and equalize pressures.

New cap is now sealing the system shut, and coolant is no longer rushing towards the reservoir. That is why cap should not be open immediately when engine is hot.