How good is your water pump?

[Ron]

No, there is no advantage. In fact, you will cause engine damage in the long-term with a lower temp thermostat.

Proper combustion inside of the chambers relies upon heat. Too cold of temperature results in a slower, and ultimately an incomplete burn. Aside from a slight bit of negative fuel economy, over time you will end up with severe carbon deposits on the piston and exhaust valves. The result is pre-detonation since carbon doesn't cool quickly, and eventually a loss of compression when the exhaust valves can't fully close due to the build-up.

Save for commercial trucks, manufacturers no longer place actual numbers on the temperature gauges for this very reason of drivers perceiving their vehicles as running too hot @ 220. It's the proper temp, and one that other vehicles run at. 235 starts to be the danger zone, but your car is running perfectly fine. Ask yourself why you "consider" this to be too hot of a temp.

Besides, you also have several feet of aluminum piping and hoses that also bleed heat off, aside from your radiator. Don't worry, your car is functioning normally.

+1!
AND, 190F thermostats are the new "standard rate" because it helps get the O2 sensors on later model cars up to operating temp sooner, allowing the engine management to engauge sooner (closed loop).
The thermostat's only job is to get the engine up to operating temp. After that it is all up to the radiator and fans. After it opens fully (212F for a D), it just sits there...so there is nothing to be gained here.

========

The 4 pumps:
I think you would have to test the 4 pumps to know which one has the highest flow. Look at the impeller fins closely. They have different shapes and total areas.

The pumps are more than adequate. E.G., The factories often use the same pump for 4-8 cylinder engines and on newer higher horse power engines as they come along.....

It is not true that you can have too much flow WRT heat transfer! (Hard to out run infrared, J/K;-)
More flow is good, but and there is a down side to increasing the flow after reaching an adequate rate. More flow means more horse power, which means more heat. Racers found this out years ago...all this is somewhere on the Edelbrock sites.

FWIW, I agree with a better radiator/fans as being the way to go, imho.

EDIT: TYPO 112F->212F

[dn010]

If you're worried about the distance, you can move the shaft/impeller to whatever desired distance you want to; nothing is being held permanently (shaft, bearing, impeller), it's all press fit.

There is also a limit to how far back the impeller can go, ask me how I know.

[David T]

If you move the impeller too much in one direction it will not be good for the other side. There is a manufacturing tolerance because you can't have the impeller too close to either side. That said, if you are running hot the only way the thermostat can be the problem is if it doesn't open all the way or is stuck closed. When it gets to it's set temperature it is supposed to be wide open so if you have a 180 and the motor is 220 that thermostat is supposed to be wide open. Easy to test. Pull it out, stick it in water on a stove with a thermometer and heat it up. Using a lower temp thermostat only means it will be fully open at a lower temperature. If you are overheating either you are making too much heat for the cooling system to dissipate or the cooling system can't handle the heat because it has a defect. Typically the radiator gets plugged up on either the air side or the water side. If the radiator is old just replace it. If it is not old, clean it. Make sure both fans work, are turning it the correct direction and the fan blades are firmly attached to the motor shaft. Make sure nothing is blocking the air intake for the radiator like debris or a license plate. As bad as the cooling system is in the Delorean, it is adequate but it must be working properly. Make sure the radiator is bled so it can fill with coolant.

[SBL]

Robert,

I respect your knowledge as a long time contributor. Nevertheless, I doubt that the PRV was so perfectly engineered that it could not withstand a 10 deg F decrease in operating temp. We know that our cars run fine at lower operating temps in the frigid North, and higher in the new age temps of the deep South. So, there is some degree of tolerance to any spec that is stated. I am only asking to nudge that temp down for those of us that suffer in very hot climates. Why do I think 220 deg F is too hot? Well, much more than that temp and I begin to smell and hear boiling fluid. And the engine is too hot to work on for hours after a prolonged run at 220 deg F. A previous DeLorean that I had never got above 160 deg F and was so reliable in stop and go traffic on the hot summer DC beltway. I am not sure why it was that way, but I felt comfortable making such trips, and right now in South Florida, I less comfortable.

[SBL]

Ron,

My Technical Information Manual states that the thermostat is fully open at 212 deg F (not 112 deg F as in your post). Will you clarify? Probably a typo. Nevertheless, fully opening at 202, for example, surely would not hurt anything. Agree that once open, it is up to the other components to keep the engine cool. I have found, though, that getting the thermostat to fully open earlier helps to keep the quasi-equilibrium at a lower operating temp. This may be due to the concept that once it gets hot (near boiling), it stays hot, and it is hard to get it down. If it never gets there, it is easier to move down when the fans kick in, or load changes, etc. There is clearly a hysteresis both at the otterstat, the thermostat, and ultimately the full cooling system.

[DMCVegas]

Steve,

First off, thank you for the complement. I do appreciate it, and of course, we're all here to learn from one another. With my question of why you thought that the car was running too hot, it wasn't to antagonize. Just simply to have a starting point to demystifying engine cooling systems. Like I say, modern cars don't even print numbers on their coolant gauges any more because of this specific issue of people being concerned with engines running too hot when they see those numbers.

Getting right to the point, engine thermostats don't regulate water temperature by keeping your engine cool; they regulate temperature by keeping your engine hot.

It seems counterintuitive, I know. But it's the honest truth. Your cooling system is designed for maximum efficiency in dumping excess heat out of the engine (past what gets expelled through exhaust). The engineers will calculate how much heat your engine will generate under the maximum load the engine will be placed under. This means your vehicle loaded down and meeting it's GVWR. Then add to that resistance from climbing a steep hill, excessive environmental temperatures, all accessories on the engine running, and then finally additional heat from the condenser coil that pre-heats the air.

Now all of that is great, but what about when you're just cruising around at much lower speeds? In that case the radiator is overcooling the engine. Which then leads to the problems of poor emissions, and of course engine damage from carbon deposits. This is where the thermostat comes into play. Once the radiator has done it's job and gotten the temps below a range, your thermostat will start to close and restrict coolant flow to help keep the engine hot. Once it gets too warm, the thermostat opens back up to let the hot water out, and then the engine will suck cool water in from the radiator...until it gets too cool again. Thus the cycle continues. Otherwise, why would we need a thermostat at all? Even air-cooled VW engines use thermostats to accomplish this same thing.

If you had a car that was running 160°F, chances are that there was actually a malfunction with the thermostat. When some thermostats fail, they refuse to open. But others will refuse to close and fail in the open position to avoid engine overheating. That temperature is not good.

If you're hearing bubbles in the cooling system, that isn't normal. Nor is smelling burning coolant. Chances are that you might possibly have a slow leak around the Y-Pipe O-Rings. I've had this same problem, and replacing those rings cleared it right up.

Another thing to consider if you have a car that runs hot would be to pull your radiator out, and blast it and the condenser coil fins out with a pressure washer. Over time mud, bugs, tar, and other debris can clog your condenser and lower both the cooling capacities of your A/C and your engine cooling system. Yes, a lower temp thermostat certainly might circumvent that issue, but there is still an issue present that isn't being addressed. One that can lead to long-term engine damage. Either with the carbon build-up, or an outright failure of the cooling system itself. Example being packed fins reducing airflow and getting worse and worse.

Yes, I absolutely understand how hot it gets down south. Most people don't even realize that even the Alabama shore itself is parallel with the Sahara desert, and Florida goes even further south. But driving out here in Las Vegas where I'm in the Mojave, I can tell you that other than a 3-core radiator upgrade, everything else remained stock and I never had any problems idling in traffic, or climbing mountains. Yeah, it takes at least 3 hours to cool down before I ever touched anything, sure. But even after parking in a hot garage with a couple of cars and heat-soaking the engine, it would fire right up and still remain cool. That's how I know you'll be fine.

[Ron]

Ron,

My Technical Information Manual states that the thermostat is fully open at 212 deg F (not 112 deg F as in your post). Will you clarify? Probably a typo. Nevertheless, fully opening at 202, for example, surely would not hurt anything. Agree that once open, it is up to the other components to keep the engine cool. I have found, though, that getting the thermostat to fully open earlier helps to keep the quasi-equilibrium at a lower operating temp. This may be due to the concept that once it gets hot (near boiling), it stays hot, and it is hard to get it down. If it never gets there, it is easier to move down when the fans kick in, or load changes, etc. There is clearly a hysteresis both at the otterstat, the thermostat, and ultimately the full cooling system.

Yes, that was a typo. Sorry!
(fixed)

I have to disagree. Fully opening at 202F means the thermostat is rated ~180F. This means that the engine is not brought to temp as quickly as intended, causing the engine management to engage late. The lubricating system will suffer if you go lower than 180F. Both can harm the engine. The gas mileage, environment, and drivability will also suffer.

Consider the following. (I'm babysitting a fire pager and got bored. Note it is only my understanding of how things work.):

TEMP-FLOW.jpg
The area shaded in Red reflects the range during which an underrated thermostat will defeat the engineers intent and be detrimental WRT to the things Robert and I mentioned.

Both shaded areas, together, represents the range during which an underrated thermostat results with more flow than the OEM rated thermostat. As the engine first warms up, both thermostats will open and close several times during this period as cool water is first allowed to pass. The fans will cycle a few times as well. These will make any lag between a 190 and 180 become insignificant by the time they have both opened fully (212F). Regardless, from ~212F on, the flow is the same for both thermostats. The performance of the radiator, fans and other cooling system components are also the same. Here, the only variable left to consider in the cooling function is the initial input temperature. I believe it would be the same for any thermostat due to the reasons above. If they were not (due to hysteresis caused before they were both fully open earlier, momentarily loading one engine, or anything not constantly raising the input temp on one but not the other), the system would still bring both to the same temp, given a relatively short period of time to perform (even if it means raising the temp). Since your concern is temps well above 212F, there is nothing to be gained with any thermostat you choose because they have no influence on coolant flow/temperature after they are fully open, imho.

Again, I may have something way off. Just offering my $.02!

[David T]

All of the clearances in the motor were designed for a small temperature range. For example the rings. Once heated up that gap is closed but get hotter and that ring starts to bind and the pistons can't go up and down anymore. It gets hotter and hotter and then the motor seizes up. Run too cold and gasses leak past the gaps. Your goal should be to get the cooling system working as designed, not to make changes in it without understanding all of the consequences. The thermostat is meant to help warm the motor up quickly and in cold climates to keep the motor hot. In cold climates the cooling fan motors aren't running if you are moving over about 30 MPH and the A/C is off. The radiator could actually overcool the motor, the thermostat prevents that by closing if it senses the motor is too cool.

[FABombjoy]

Unfortunately the available engine literature is ambiguous on the subject.

Volvo TP30430-1 specifies the three thermostats as "Type 1" "Type 2" and "Type 3", with low opening temps at 178, 187, 196 respectively. In this greenbook, further references to three types are limited to the B27F motor and vacuum routing. But there isn't really a confirmed correlation between these different types across contexts.

The reconditioning manual TP30447-1 only mentions the types with regard to camshaft selection and valve clearance. No references to bearing clearance changes.

The B28 reconditioning manual specifies the same valve clearances as the "Type 1" B27. This doesn't make a strong case for "type 1" correlating between thermostat temp and emissions/vacuum systems.
The crank & connecting rod specs are the same between B27 and B28. 70's through the 80's these things are static.
The ring gap specs are the same.
This B28 manual has no thermostat temp references.

Apart from "hotter oil, happier oil", there doesn't appear to be any tolerance variations necessitating hotter or cooler thermostat.

Just to kick this into the circle, Volvo specifies 10w-30 or 15w-40 oil and not 20w-50. Perhaps this revised oil weight follows the hotter t-stat temp?