Warm up the car, drive along, all ok. Stop for red light, temp spikes to 230+ within a minute, soon as we move, temp drops back to normal. Checked out fans on radiator, jumped out the temp sensor, they run constantly now, but temp still jumps, and then settles down when moving again within a minute or two. It's not the relay, as the fans keep running al lthe time. Bad gauge? Doesn't seem likely as the event is repeatable, exactly. Coolant level? Nope, resevoir is half full, as per instructions. Water pump? Hope not, as revving engine at rest does not seem to effect temp one way or the other. Ideas? Things to check?
Possiable t-stat problem awell. You may have a tight or binding t-stat. When at idel coolant isn't circulating as hard as when under load. This could cause the stat to close when circulation pressure relaxes. (hard to explain but I think you understnd what I'm getting at.)
Coolant level/air lock. Level in reservoir is meaningless, unless system properly bled via screw in top of radiator. It's best to have the heater set to the hot position for this.
Check to see if fans are rotating the correct way, ie : pushing the air throught the radiator - a simple test is to put a piece of paper against the grille and it should be sucked up against the grille. The radiator could also be the problem, check to see if the fins are "clogged" up with debris, flies etc. MW
Thermostat is a definite possibility. I put about 800 miles on it in the lasy month, after a majir rebuild, so bleeding the system seems more remote. Can't be the sensor, I've jumped it out. Fan is running all the time right now in an effort to diagnose the problem. I ordered a thermostat, but I could just remove it for the moment to see if that alleviates the problem, right? Better to attack one possibilit at a time, I think. thanks guys, back to the garage for me.
Since it worked fine for the 1st 800 miles, this seems less of a possibility, but I'll check it this PM. Thanks
Believe it or not, check the alternator output too. I had the exact same problem with my Boxer that turned out to be both of the alternators were going bad and not putting out enough current to run the cooling fans at the proper speed when at low speeds such as in traffic or at idle while at a traffic light. Like your car, once I got moving the temp quickly dropped. That indicates that your radiator is fine, but your cooling fans are not working as they should. After I had the alternators rebuilt, the fans speed increase and the car starting cooling properly. This was after I had already had my radiator re-cored and replaced the thermostat to no avail. FYI, the cooling fans draw more current than any other thing on the car. Just go to any Advance Auto Parts and they will check the alternator for free.
"I ordered a thermostat, but I could just remove it for the moment to see if that alleviates the problem, right?" Dave -- Make sure you understand how the thermostat works in your 246 before trying this -- often "removed" does not give the same result as "fully open" (which is what you're trying to simulate). Don't know 246 specifically, but on other F the thermostat is more of a spool valve gizmo (that shifts flow between two paths by both opening and closing valves) rather than an on-off gizmo (that when removed gives the "on" state). When you're "moving again" you get the benefit of improved circulation and the benefit of more airflow thru the radiator (and over everything else). To follow up on Tom B.'s thought -- what happens temp-wise if you just raise the engine speed to say 2500~3000 RPM for a while without moving the coach forward (or how about, if you come to a stop and keep the RPM up, is the rate of temp increases faster or slower than if you just let it idle after stopping)?
I also wouldn't drive around without a thermostat as you would more than likely bypass the radiator altogether being that the radiator is at the front and the water circulation would only circulate around the motor and not run down the front to the radiator which also would be a quick way to cook your head gasket.I might be wrong about this theory but in the GT4 this would be the case(Im assuming the set up is the same)It might be the temp sender and not the guage itself.Does oil temp rise at the same time? hope this helps.
Bleed the radiator. An air pocket can really reduce cooling capacity if you have too much air trapped in the top. Comments are correct on t stat. You can check operation in boiling water on the stove. Don't remove it completely.
An air pocket or bad thermostat problem would cause the temp to go up regardless of whether you were at idle or moving. A problem with the fans will only show up at low speeds or at idle though. See my post above
Actually on an unrelated note, I've had some other vexing electrical problems that we're working through, so fan speed and voltage could absolutley be a problem. I'm putting in a new alternator fuse block this weekend, along with new cables, which may help too. Stay tuned!
Re-wired the alternator fuse block, and the system is charging like it is supposed to. Hooked fans back up to the thermal switch, as that did not seem to be the problem. They ran very strong when I bypassed the switch. Ran car up to operating temperature, gauge went to 195 degrees, then sat there a minute, then spiked to 230+. Checked fans, they were not running. Put a hand, carefully, on the radiator, and it was COLD, engine hot, radiator absolutely cold. So thermal switch is not going to work on a cold radiator. Looks more like the thermostat now than ever, as no hot water is circulating until the car gets very hot. Or am I still chasing the wrong way? Water pump was rebuilt with the engine 800 miles ago, but I asked the mechanic today if her replaced the thermostat and he said no, he had not.
don't mean to sound like a monday morning QB but anytime waterpump work or cooling system work is done you should replace the thermastat if it is aged. I still am struggling with the description of your problem though, if it is a blockage why does the car not over heat when you are moving? I can't imagine airflow cools a rear placed engine that much. obiviously it helps the radiatior but you say the rad is always cool
Now we're up to a blockage or bad impellor. So far, I bypassed the temp switch on the radiator, fans run all the time. I replaced the thermostat, burped the hoses, bled the radiator, no bubbles. Checked voltage to the fans, it's ok. Grounds are good, so, I'm not thinking it is a fan/cooling problem. The hoses to the radiator get hot, but the radiator itself is not very hot, just medium warm. I can lay my hand on top of the radiator, it's warm, but not hot. So, now it looks like the radiator itself may have a problem, blockage, whatever, or the impellor on the water pump may have failed. We replaced that when we did the major service 800 miles ago. A simple flush of the radiator ain't gonna get it done, so we're talking overhaul, or some kind of ultrasonic cleaning for the radiator. I'm going to do some digging on here to see what others have done in this instance. Advice??
You're not getting coolant to the radiator OR it's not being cooled, right? How old are the hoses? They can collapse from pressure; old hoses can do this. Can you varify collant goes throgh the radiator? If yours is like my Europa one, there is a baffle by the input/output that can collapse and the coolant never circulates correctly. I'm not familliar with a Dino radiator but in mine, this isn't unheard of. Is the waterpump belt driven? If so it may be a little loose. If you idle at say 3500 RPMS, does the temp spike go down, or only when you drive? Ken
I know you said it is repeatable so it is not necessarily the guage, but I would check to make sure you are trully getting a correct reading from the guage. Also, the amount of work you had done to this car - restoration - a loose ground could be giving false readings. Before you can solve any problem you really need to know if the information you are using is correct. As this car is not overheating, I would say you do not have a closed thermostat - I would be annoyed they did not replace the old one.
If it hasn't already been done, remove the radiator and take it to a radiator shop. For less than $100, they will rod it out, repair any leaks and repaint it. Just did mine a year ago on my '76 308. It was doing the same thing, heating up while sitting still (not enuff water moving through a clogged radiator) then cooling down once it got moving (limited amount of circulation was enuff to cool down the water). While you're in there, replace all the old coolant hoses. End of problem. My car temperature is so steady now, even on 100 degrees southern calif days.
Hoses are all new. Coolant must be going through somewhat, the bleeder valve will spit out coolant once the radiator warms up. ON idle, temp rises, on road, temp drops, don't know about revving it when sitting still.. Haven't tried that. She's under the cover for today. Seventeen skinned knuckles and a new TV inbound (gotta set up the surround, etc.) has drawn an end to todays automotive festivities. Tomorrow however, we'll see what happens.
It's almost a certainty your radiator needs cleaned out and it can only be done at a radiator shop. You gotta be careful though, you can get gouged for this. After telling one shop it was from a Ferrari, the guy quoted $650 to do the job. To keep from getting gouged, take it out of the car yourself; call around to radiator shops until you get a reasonable price; if they ask what kind of car it's from do what I did: tell them its out of an old Fiat station wagon. Mine ('76 308) cost $79, and they did a beautiful job. Rodded it out, resoldered several weak spots, pressure tested it, straightened the vanes and repainted it semi-flat black.
