Funny Overheating Problem with Carby V8
Posted: Tue Jul 26, 2011 2:22 pm
I posted this over at an Australian Land-Rover forum that I'm on, and when someone said that this may be the start of a head gasket leak I thought it would be a good idea to post my question here, since such gasket leaks are no doubt well known by some!
Here is what I posted in the other forum:
I've been chasing this problem since last year now, but every time I think I fixed it, it's still there.
1983 Rangie auto, with plain old carby V8 and aircon. When I got it, it had a metal fan on the water pump from something else that somebody had put on. I replaced the radiator with a brand-new one - proper aircon spec - and a new Genuine Parts 74C thermostat, and put in a capillary type temperature gauge as the standard one didn't seem to know what it was doing, (as usual with these old gauges). And I also put in a Watchdog TM2. As well, I gave the engine a good flush and bypassed the heater by connecting the two pipes at the back of the inlet manifold, which is what the parts book shows for V8 Defenders with no heater, so that should be okay.
With the new gauges, I could see this funny problem. Everything would be fine when idling, or cruising around town at 50kmh, but out on the highway it would quickly heat up to almost 100c, and then the temperature wouldn't come down again with town driving or idling. I finally worked out that the new thermostat wasn't opening all the way and put in one that would, and the problem was much better. But now it was after a highway drive that it would start running too hot in town.
Not long afterwards, I replaced the water pump as the old one developed a squeak, but the new one had a different stud pattern and while the original double pulley would fit, the old metal fan wouldn't. So I went to EL Falcon thermos, which seemed okay - until a drive to Broome on a 26C day and they had to be left switched on for a good deal at the end of the trip, so obviously something was still wrong.
So . . . thinking that perhaps the thermos weren’t up to it for some reason, even though other guys are happy with them, I got the original type plastic fan and viscous unit and shroud, and found that, after all, that hasn't made any difference. It's still a concern now as the temperature is fine while highway cruising but then it heats up rapidly while town driving afterwards, to the point where I'll manually switch on the aircon fans to keep it at 92C, and this isn’t in hot weather. Otherwise it can hit 97C on the Watchdog and that’s too high for me.
Using a laser thermometer, the most heat seems to be around the thermostat housing and the bypass hoses - those two hoses that go into the back of the timing cover. It's tempting to think that it's the new new thermostat not allowing enough flow, or maybe the new radiator isn't so good, since it’s the new parts you should suspect first.
So now I’ve got a new rad, water pump, thermostat, hoses, belts, viscous unit, fan, cap – in fact, everything you can replace except for the actual engine, which is fine by me. The engine heats up at a normal rate, and is okay around town until I get back from a highway run. It doesn’t seem to run too lean and I haven’t found any intake leaks, (unless the charcoal canister is no good).
And now I’m very tempted to put in a thermostat with the middle cut out to get better flow . . . but I realise that’s more of a bandaid solution. I might put the old radiator back in soon, just to see what happens - I’m pulling my hair out over this one!
Here is what I posted in the other forum:
I've been chasing this problem since last year now, but every time I think I fixed it, it's still there.
1983 Rangie auto, with plain old carby V8 and aircon. When I got it, it had a metal fan on the water pump from something else that somebody had put on. I replaced the radiator with a brand-new one - proper aircon spec - and a new Genuine Parts 74C thermostat, and put in a capillary type temperature gauge as the standard one didn't seem to know what it was doing, (as usual with these old gauges). And I also put in a Watchdog TM2. As well, I gave the engine a good flush and bypassed the heater by connecting the two pipes at the back of the inlet manifold, which is what the parts book shows for V8 Defenders with no heater, so that should be okay.
With the new gauges, I could see this funny problem. Everything would be fine when idling, or cruising around town at 50kmh, but out on the highway it would quickly heat up to almost 100c, and then the temperature wouldn't come down again with town driving or idling. I finally worked out that the new thermostat wasn't opening all the way and put in one that would, and the problem was much better. But now it was after a highway drive that it would start running too hot in town.
Not long afterwards, I replaced the water pump as the old one developed a squeak, but the new one had a different stud pattern and while the original double pulley would fit, the old metal fan wouldn't. So I went to EL Falcon thermos, which seemed okay - until a drive to Broome on a 26C day and they had to be left switched on for a good deal at the end of the trip, so obviously something was still wrong.
So . . . thinking that perhaps the thermos weren’t up to it for some reason, even though other guys are happy with them, I got the original type plastic fan and viscous unit and shroud, and found that, after all, that hasn't made any difference. It's still a concern now as the temperature is fine while highway cruising but then it heats up rapidly while town driving afterwards, to the point where I'll manually switch on the aircon fans to keep it at 92C, and this isn’t in hot weather. Otherwise it can hit 97C on the Watchdog and that’s too high for me.
Using a laser thermometer, the most heat seems to be around the thermostat housing and the bypass hoses - those two hoses that go into the back of the timing cover. It's tempting to think that it's the new new thermostat not allowing enough flow, or maybe the new radiator isn't so good, since it’s the new parts you should suspect first.
So now I’ve got a new rad, water pump, thermostat, hoses, belts, viscous unit, fan, cap – in fact, everything you can replace except for the actual engine, which is fine by me. The engine heats up at a normal rate, and is okay around town until I get back from a highway run. It doesn’t seem to run too lean and I haven’t found any intake leaks, (unless the charcoal canister is no good).
And now I’m very tempted to put in a thermostat with the middle cut out to get better flow . . . but I realise that’s more of a bandaid solution. I might put the old radiator back in soon, just to see what happens - I’m pulling my hair out over this one!