My original dash cluster was in very poor condition, so I changed the dash to a front removable insert with after market gauges.

The water temp runs about 210 - 215 using the stock rear temp sensor hole after stabilizing engine temp by driving 30 mins or so, whether A/C is on or off and whether A/C condenser pusher fans are on or off. I have a 190 Beck/ Arnley 1430354 thermostat.

I used an infrared temperature gauge and measured the surface temp of the brass sender and it agrees +/- 3 degrees with dash gauge. I then measured the thermostat housing and the small removable cover with 2 bolts right below the thermostat housing and found them at 198-202 degrees. These measuring points are an inch or so forward of the exhaust port.
The top radiator tank reads ~190, the bottom ~ 160.

The exhaust manifold as it leaves the head ports are ~ 400 deg.
I then measured the opposite side of the head and found the temp about 195-200.

I think the factory location of for the temperature sensor is too close to the exhaust port and giving a false high reading.
Maybe this is why so many people complain about the stock temp gauge reading so high.

I think I may drill and tap the small removable cover with 2 bolts right below the thermostat housing, it is about 1/8" thick so not many threads.
Any else tried this?

I'm wondering whether a 30 deg F drop in coolant temp, as it flows through the radiator, is a bit much, possibly hinting at restricted flow somewhere. Have you taken a good, strong (high volume) garden hose and "flow tested" the radiator and the engine? The thermostat may have to be removed to properly test the engine flow.
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Current rides: 2005 Volvo S80 2.5T, 2003 Volvo V70 2.4NA, 1973 Volvo 1800ES (STILL not road worthy!)

I reread my notes and that temp on the bottom temp was actually the condenser fan temp switch bulb (about 1/3 from bottom) and was actually 157. The probe is clamped to the radiator side frame and is aimed toward the center of the radiator but it doesn't touch the core, maybe 1/8 to 3/16" from core. I usually push the probe through the fins but this staggered fin construction doesn't leave enough room to push through the fins with risking tube damage.

The actual core was about 10 deg warmer. I had the stock 4 blade mechanical fan running and the 2 condenser pusher fans running. Made one 5 mile trip on the interstate at 60 mph and the temp dropped maybe 3-5 deg.

I "flow tested" the radiator off the car while it was apart. Not very scientific, but I would say it flowed out about like any other I have flushed off the car.

The strange thing is temp does not vary much with the load, pulling hills, slow driving, interstate driving. or just sitting and idling.

The electric fans cycle when idling.

The thermostat you are using is higher rated than that used by Volvo. As such it looks as if your gauge is reading correctly. Try the correct 180/82º one. The lower temp one spec'd is a 72/160º. Keep in mind that your A/C will put more demands on your cooling system.
Always use a thermostat with the correct bypass plunger. Agree with Eric re the correct length rad cap. This is an essential part of the system, especially if you aren't using an expansion bottle.
Radiators should be backflushed i.e. from the bottom. Just a comment in case you haven't done it that way round.

Try a cooler thermostat.

I have 160 F° thermostats in stock.

Do you have the correct 1" reach radiator cap? 3/4" reach caps are easily available, but most auto parts stores have to special order a 1" reach cap.

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Eric
Hi Performance Automotive Service (formerly OVO or Old Volvos Only)
Torrance, CA 90502
hiperformanceautoservice.com or oldvolvosonly.com

I don't want to run my engine at 160, good for performance driving but too cold for everyday use. Engine runs much better at 190-195, better fuel economy, crankcase condensation eliminated much quicker etc.
Ambient temp yesterday was in mid 60's.

Unsure of my radiator cap, but it is immaterial because I am not boiling over or losing water, would not affect engine temp, only keeps the water in the system and raise boiling point.

I have only driven the car about 60 or 70 miles since I bought it last spring.
Stock gauge read hot then.
Now with paint and body and reassembly finished I am shaking out bugs.

The radiator looks like it is probably the original style (2 staggered tubes).
Cooling system internals are squeaky clean. (this was a one owner car)

Looked at water distribution tube a few months ago, and probed with a bent wire on all downward passages were clear (couldn't remove without damage due to crimp).

Weber carb and Peirce manifold were on it when I bought it, I know I need one step richer on the primary jet (has a flat spot before the secondary kicks in).


My good friend has a 62 544 and his factory gauge always reads on the high end.

Ignition timing could affect temp. While apart I checked true TDC and found my double groove bottom pulley (had ARA A/C since new) off a bit. I marked correct TDC and set 12 deg BTDC. Total advance at 3000 rpm ~ 33 deg. All sounds good to me. Doesn't ping. Dwell about 57 deg.
In fact the engine runs great just a little too hot unless I go by the thermostat housing temp, then it is in spec.