Series 3 running hot

[Paul Rossmann]

The old girl is running hot. In stop and go traffic the needle quickly moves into the lower part of the red. Once moving, everything seems fine. I have flushed the radiator and engine cooling system and replaced the water pump and thermostat.

I ran the car for 2 years with just an auxillary electric fan and she did okay. The thermastat (for the electric fan) gave out, and I put the original mechanical fan back in, but to no avail.

Any ideas.

[Jim-ME]

For the cost, I would replace your temp sender before going any further.
Jim

[greenmeanie]

A couple of things to check.

1. This may be offensive but check the mechanical fan is the correct way round so that it pulls air and doesn't push it.
2. Do you have the cowl in place - it makes a huge difference to the fan efficiency.
3. When she starts getting hot feel the top and bottom radiator hoses. If one is significantly cool you have a blockage.
4. Hold your hand close to the radiator (Don't touch it because that will hurt) and feel for cool spots. If you are fancy and part of the modern world you can get one of those optical thermometer gun things to take readings.
5. How new are the hoses? They can collapse internally partially blocking the coolant flow.

Flushing a radiator can help as part of maintenance but once blocked it very rarely ever shifts the problem. A clogged radiator really needs to be rodded or replaced.

The series cooling system is overbuilt for the original engine and if in good order tends to overcool if anything. A couple of years ago I replaced the water pump, hoses, fan and radiator due to an errant socket left on the crankshaft end nut (Not one of my prouder garage days and a bit of a brown trouser moment with the bang when it came off.). Now I have to put the radiator muff on when it falls below 50° and she only gets up to maybe 3/4 on the gauge during the height of the Phoenix summer.

Cheers
Gregor

[Paul Rossmann]

Thanks, I will give that a try, but the temp starts at "zero" and progresses up normally. When the car is moving along at 35-40 the temp is normal (after a few minutes). It is when the car is stopped or in stop-and-go traffic. I did pull teh sensor to make sure it wasnt just gunked over, and it looked clean.

[Tim Smith]

Could you have the idle set too lean? Or is the idle set too low so that the fan doesn't pull enough at the street lights?

Kind of guessing here.

[singingcamel]

A couple of things to check.

1. This may be offensive but check the mechanical fan is the correct way round so that it pulls air and doesn't push it.
2. Do you have the cowl in place - it makes a huge difference to the fan efficiency.
3. When she starts getting hot feel the top and bottom radiator hoses. If one is significantly cool you have a blockage.
4. Hold your hand close to the radiator (Don't touch it because that will hurt) and feel for cool spots. If you are fancy and part of the modern world you can get one of those optical thermometer gun things to take readings.
5. How new are the hoses? They can collapse internally partially blocking the coolant flow.

Flushing a radiator can help as part of maintenance but once blocked it very rarely ever shifts the problem. A clogged radiator really needs to be rodded or replaced.

The series cooling system is overbuilt for the original engine and if in good order tends to overcool if anything. A couple of years ago I replaced the water pump, hoses, fan and radiator due to an errant socket left on the crankshaft end nut (Not one of my prouder garage days and a bit of a brown trouser moment with the bang when it came off.). Now I have to put the radiator muff on when it falls below 50° and she only gets up to maybe 3/4 on the gauge during the height of the Phoenix summer.

Cheers
Gregor

Good Advice here

[Paul Rossmann]

Thanks all for the advice. This is a real stumper as the cooling systems are so simple. My engine idle is around 1100 so it isnt that. Brakes arent binding (the car gets hot standing still) I have replaced the waterpump and thermostat. The gauge climbs up normally, so I dont believe it is the sensor. The other day when the car was hot, after very carefully opening the radiator cap, I removed the lower hose to drain the radiator quickly and ran a garden hose (cold) into the radiator while checking for "dead" spots. The radiator got cool evenly so I cant figure that out. I hate to go to the expense of a new radiator, but I cant figure this out. Is there anything with the heater hose, or heater itself that could be doing this? Again, I appreciate the input.

Rovering against better judgement,
Paul

And yes, the fan is the right way round. I actually thought of that in the middle of the night last week and had to go out and check (sick, huh?).

[greenmeanie]

Your idle seems pretty high @ 1100 rpm. The book quotes something like 600rpm for the early pre emissions trucks and 825rpm for the later models with PCV valves & charcoal canisters.

If that is as low as you can get her to go smoothly I would suggest that you are badly out of tune. I would go back and play the timing/fuel/idle game and see what that does for you. It's a cheap place to start.

Cheers
Gregor

[SalemRover]

It seems that when there is good airflow your cooling system works fine. If it was blocked you would not cure it quickly by getting up to speed. It could be that going back to the stock fan you simply uncovered a problem that was simply masked by the electric fan. Idle being lean is a good idea to check. Lean exhaust should be fairly easy to diagnose, if unsure just run a little richer on the carb noting how much you moved the screw so you can go back. Lowering the idle RPM back to stock (even if it is rough... you can deal with that seperately) should also help as well.

Good Luck,

Jason

[Paul Rossmann]

Just drove the Rover home from work. She was not overheated, but in the upper range on the gauge. As soon as I stopped the car, I got out and felt both the upper and lower radiator hoses. The lower hose was noticably cooler than the upper hose (warm vs. hot). I am now thinking that in addition to the possible idle/timing/lean mixture issue, that it may well be the radiator. Perhaps a partial blockage? Can this be reasonably repaired? Hmmmm?