tlava Posted May 10, 2012 Share Posted May 10, 2012 HI Folks-- OK--Sorry to bring this up again, but this really has me puzzled. I'm driving along the mountain roads, everything seems fine--temp may rise to around half or slightly over, but then the fan clutch seems to kick in and bring it back under. After about maybe 40 mins of this, I'm on the freeway, cruising along 65-70; temp starts climbing--above half, hangs there; gets really close to the danger zone by the time I get off--I idle about a minute to see if the clutch will kick in--no change; I pop the hood, shut off the engine, walk back to the engine compartment, and the fan is still spinning a bit; I turn it with my hand and it turns quiet easily; I wait a minute, turn it again, and it is tighter--the engine has been off now for about a minute. I get back in, start the engine again, and now the fan clutch has apparently kicked in and begins to pull the temp down. Why didn't it kick in when the temp had risen to just below the danger zone, and stayed there for at least 5 mins? why did it kick in only after turning the engine off, and then back on again? Again, I have a new thermo, new fan clutch, and new radiator (v6 Nissan engine)--I know folks have said not to worry, but this just doesn't seem right.. I had the cab gauge checked at a shop when I got the RV inspected (temp at the time was 165 they said the gauge was right where it should be). Could the issue here with the fan clutch and thermo somehow not matching up? Tom Quote Link to comment Share on other sites More sharing options...
5Toyota Posted May 10, 2012 Share Posted May 10, 2012 i dont know much about that moter i wonder if the fan clutch even though new is defective or if it is the wrong one for that unit Quote Link to comment Share on other sites More sharing options...
waiter Posted May 10, 2012 Share Posted May 10, 2012 When your driving at highway speeds, that temp should stay fairly constant. If it heats up again, try this, Turn your heater on full blast. Leave the blower OFF) This bypasses the thermostat, and gets at least some water into the radiator. See if the temperature drops. (could indicate bad thermostat or air pocket. Also - wait and then turn the blower on full blast, This should blow out very hot air.. From what you just described, it sounds like the fan clutch is not sensing the heat (hot coolant not getting into radiator), OR, the clutch is defective. If there is no hot water in the radiator, then the clutch should idle and spin freely, because it thinks everything is cool. If the thermostat is sticking, or the thermostat was installed upside down, it could be preventing water from getting to the radiator. (If you turn the heater on full blast, it bypasses the thermostat and will help NOTE - Some engines require a special "purge" procedure to ensure coolant is full and no air pockets exist inside the engine block, I'm not sure if yours is the case. John Mc 88 Dolphin 4 Auto Quote Link to comment Share on other sites More sharing options...
tlava Posted May 10, 2012 Author Share Posted May 10, 2012 thanks for that information. But a couple q: why would there be no hot water in the radiator? Also, what about the fact that if I turn the engine off, the clutch actually seems to start tightening afer a minute, and then brings down the temp when I turn restart? so it does seem to be kicking in, bugt no t quickly enough, or nod while air is circulating through the radiator? Quote Link to comment Share on other sites More sharing options...
waiter Posted May 10, 2012 Share Posted May 10, 2012 If the thermostat is upside down it will restrict water flow into the radiator. I don't know about your particular engine (Nissan I think you said) but there are engines with cooling system that if they are not purged correctly, an air pocket around the thermostat could keep it from sensing water temperature and it won't open correctly, OR, an air pocket around the pump will cause it to cavitate and it will not pump water correctly. On your fan clutch, Yes, your correct, Keep in mind that the hotter the clutch gets, the harder it should be to turn. Theory - If you have very restricted water flow through the radiator, the radiator will be at air temperature (More on this in a second) . When you turn the truck off, the ambient temperature of the engine could start heating the clutch and make it a little harder to turn. OK - Another test - after you shut the truck off, very quickly, pop the hood and put your hand on the radiator. If it burns your hand, you have a clutch problem, if you can hold your hand on the radiator, you have a circulation problem. John Mc 88 Dolphin 4 Auto Quote Link to comment Share on other sites More sharing options...
Derek up North Posted May 10, 2012 Share Posted May 10, 2012 ... put your hand on the radiator. If it burns your hand, you have a clutch problem, if you can hold your hand on the radiator, you have a circulation problem. John Mc 88 Dolphin 4 Auto A 'Rule of Thumb' (hand?) is that if you can keep your hand on it, the temperature is ~140F. Quote Link to comment Share on other sites More sharing options...
tlava Posted May 10, 2012 Author Share Posted May 10, 2012 OK--will try that. So put a hand on the radiator cap? the top end of this radiator is I believe plastic, so might this effect things (it is a new rad, as I say, not the orig copper/alu). Another thing--a have a small tranny rad mounted on front of the main rad---Aaron suggested that might be restricting flow? doesn't cover the entire front, of course (it's may a 4x 6" piece? standard tranny cooler..) Quote Link to comment Share on other sites More sharing options...
90toydolphin Posted May 10, 2012 Share Posted May 10, 2012 top of the radiator, just be careful it might be hot ). another thing to do is when cold take off the radiator cap and then start the engine. hopefully you can see the water in the tank, if not forget the following. let it run checking the temp of the water with your finger, the water should be moving in the tank once the thermostat opens when warmed up and of course get warm. it does sound like the water in the tank is not getting as warm as the water in the engine. the gauge gives you the temp in the engine, sounds like the fan uses the temp in the tank to come on. when you shut it off the heat may finally reach the tank from the lower hose, heat rises, so after doing so it works because the water in the tank becomes hot. if you haven't talked to the shop that replaced all the cooling stuff you might want to, they should take some responsibility to make it right. i've had defective thermostats before too. you test them in boiling water and see if they open. and something brought up earlier, air pockets in the engine not allowing the water to flow properly. i've had problems with that before too, not a toyota, actually this is my first toyota. mine finally filled correctly after several times of warming up, cooling down and adding more water each time it cooled, had some room for more each time for 5-6 times. Quote Link to comment Share on other sites More sharing options...
tlava Posted May 12, 2012 Author Share Posted May 12, 2012 last time I tired running the engine w/ cap off, after about a minute, the fluid started overflowing... Another odd thing--not sure if relevant to the running hot issue: The car had been sitting for a couple weeks before this latest incident; before I started it I looked under the hood and noticed that the top radiator hose--the one running to the thermostat and top of the block---was collapsed, as if something had sucked it in---First time I have seen anything like that.. After the engine warmed up, though, it got pretty stiff.... Quote Link to comment Share on other sites More sharing options...
90toydolphin Posted May 12, 2012 Share Posted May 12, 2012 i'd replace the hose, shouldn't do that under any conditions. have you checked oil to see if water has leaked into oil? head gasket leak can cause water to bubble out of radiator. starting to sound a little more serious than first thought, hope i'm totally wrong. Quote Link to comment Share on other sites More sharing options...
5Toyota Posted May 12, 2012 Share Posted May 12, 2012 tlava you may have hit there replace that hose asap not shure about other issiues i have heard of bad hoses sucking down shut under aseleration lower ones as well sorrey i had forgoten about that. try to use good gates hoses some on the market are not good dayco is ok too. Quote Link to comment Share on other sites More sharing options...
Maineah Posted May 12, 2012 Share Posted May 12, 2012 last time I tired running the engine w/ cap off, after about a minute, the fluid started overflowing... Another odd thing--not sure if relevant to the running hot issue: The car had been sitting for a couple weeks before this latest incident; before I started it I looked under the hood and noticed that the top radiator hose--the one running to the thermostat and top of the block---was collapsed, as if something had sucked it in---First time I have seen anything like that.. After the engine warmed up, though, it got pretty stiff.... If the top hose collapsed the pressure cap or the capture tank has an issue. The ideal is to pull coolant back into the radiator from the capture tank as the engine cools. In the base of the cap there is a little brass ring with a small weak spring you should be able to lift it with little effort it is what allows the coolant to return to the radiator from the tank. If there is no water to return is just vents so if the hose collapsed it's not venting. See if you can find some one with an exhaust gas analyzer it can be use to determine if you have a head gasket problem by placing it near the radiator neck while it's running and sniffing for hydrocarbons if there is any it's a dead give away. Quote Link to comment Share on other sites More sharing options...
tlava Posted May 12, 2012 Author Share Posted May 12, 2012 Hi Folks-- Thanks--no water in oil, though I did suspect a head gasket leak exhaust side at one point though no other symptoms as far as I know--i.e. the coolant in res. seems normal. The hose doesn't collapse while running--definitely wasn't collapsed when running hot-- since I guess enough pressure build up, and this is the first time I've seen it squeezed together that way at cold start. If I had a higher temp thermo than required could that cause the hose to collapse? I'm assuming unrelated... the radiator cap is new, so assuming they sold me the right one..... I did get a leak down test at one point, at least they claimed one was done, but they couldn't tell me whether pressure was being lost through the exhaust, intake, or rings. According to the mechanic, the test was neg--all 20 percent or less except I think it was #2 cylinder which had 35 percent leakdown? I've read that 20 percent is fairly typical, though newer engines I think are quite a bit less....(this is an '86, though only 70k miles; but I guess the tech. has improved in more recent engines?), How stiff should the hose be when engine is good and hot? If there is too much pressure build up this could indicate a gasket issue, as well? but how much is too much? should I be able to run/drive with the radiator cap loose ? (I as going to try that at one point, as a test for something though can't recall what just now, but was afraid it would vibrate off....) Quote Link to comment Share on other sites More sharing options...
waiter Posted May 12, 2012 Share Posted May 12, 2012 The top hose is under pressure (water is pushing) The bottom hose is under suction. Although you don't see this problem to often, the bottom hose could collapse from the water suction (water getting sucked out of the radiator) Whats the condition of the radiator cowling, i.e. its not missing is it?? JOhn Mc 88 Dolphin 4 Auto Quote Link to comment Share on other sites More sharing options...
90toydolphin Posted May 12, 2012 Share Posted May 12, 2012 i've never known of a radiator hose not being stiff at all temps. don't run with your radiator cap loose, the water will just blow out when it warms up. the cooling system is a sealed system that creates considerable pressure allowing the water to reach 212 without actually being allowed to boil. if you loosen the cap the pressure won't be there and it will boil blowing out the coolant. another little thing is that engines all warm up once you shut them off, no more cooling of the water is taking place once you turn it off and the heat of the engine is absorbed by the water with not where to go. Quote Link to comment Share on other sites More sharing options...
tlava Posted May 12, 2012 Author Share Posted May 12, 2012 hmmm... new radiator, so I don't think so... but which part is the "cowling"? The upper part of this radiator is plastic... The top hose is under pressure (water is pushing) The bottom hose is under suction. Although you don't see this problem to often, the bottom hose could collapse from the water suction (water getting sucked out of the radiator) Whats the condition of the radiator cowling, i.e. its not missing is it?? JOhn Mc 88 Dolphin 4 Auto Quote Link to comment Share on other sites More sharing options...
waiter Posted May 12, 2012 Share Posted May 12, 2012 The cowling is the plastic duct that should attach to the back of the radiator and surround the fan. JOhn Mc 88 Dolphin 4 Auto Quote Link to comment Share on other sites More sharing options...
Maineah Posted May 12, 2012 Share Posted May 12, 2012 Coolant under pressure absorbs more BTU's and razes the boiling point. Many lower radiator hoses have spring coils inside to keep the hose from collapsing under pump suction you usually can tell by feeling it. Iknow this sounds dumb but does your heater work OK? Being higher, the heater core can become air /combustion gases bound and not heat well at all if the head gasket is leaking. A leaking head gasket does not necessarily leak water into the oil more often oil leaks into the water due to pressure differences. Coolant can be pulled in to the cylinder on the intake stroke causing steam from the tail pipe that's a pretty obvious leak and most often it causes pressure in the cooling system from engine compression. If you can't find some one with a gas analyzer a pressure tester maybe your next choice bring the pressure up to the system pressure ( what ever the cap says) if the pressure rises rapidly beyond the rated pressure the head gasket is leaking. Quote Link to comment Share on other sites More sharing options...
MAXXFabrication Posted May 13, 2012 Share Posted May 13, 2012 I vote a slowly deteriorating headgasket. they dont always go out quick like. Quote Link to comment Share on other sites More sharing options...
tlava Posted May 13, 2012 Author Share Posted May 13, 2012 Oh--thanks, this is helpful. But how will I know if the pressure is going higher than pressure rating on the cap, or when system pressure is reached? i.e., how do I measure this pressure? Yes BTW the cowling is in place, and yes the heater works fine. I did BTW have a chemical test at one point and was told I had hydrocarbons in the coolant, but others have warned me that the chemical tests are unreliable, and suggested only a sniff test is accurate. Coolant under pressure absorbs more BTU's and razes the boiling point. Many lower radiator hoses have spring coils inside to keep the hose from collapsing under pump suction you usually can tell by feeling it. Iknow this sounds dumb but does your heater work OK? Being higher, the heater core can become air /combustion gases bound and not heat well at all if the head gasket is leaking. A leaking head gasket does not necessarily leak water into the oil more often oil leaks into the water due to pressure differences. Coolant can be pulled in to the cylinder on the intake stroke causing steam from the tail pipe that's a pretty obvious leak and most often it causes pressure in the cooling system from engine compression. If you can't find some one with a gas analyzer a pressure tester maybe your next choice bring the pressure up to the system pressure ( what ever the cap says) if the pressure rises rapidly beyond the rated pressure the head gasket is leaking. Quote Link to comment Share on other sites More sharing options...
tlava Posted May 13, 2012 Author Share Posted May 13, 2012 I also tried adding White Shepherd head gasket sealer/repair to the radiator coolant about 1k miles ago, just in case, but not sure it had an effect.... Coolant under pressure absorbs more BTU's and razes the boiling point. Many lower radiator hoses have spring coils inside to keep the hose from collapsing under pump suction you usually can tell by feeling it. Iknow this sounds dumb but does your heater work OK? Being higher, the heater core can become air /combustion gases bound and not heat well at all if the head gasket is leaking. A leaking head gasket does not necessarily leak water into the oil more often oil leaks into the water due to pressure differences. Coolant can be pulled in to the cylinder on the intake stroke causing steam from the tail pipe that's a pretty obvious leak and most often it causes pressure in the cooling system from engine compression. If you can't find some one with a gas analyzer a pressure tester maybe your next choice bring the pressure up to the system pressure ( what ever the cap says) if the pressure rises rapidly beyond the rated pressure the head gasket is leaking. Quote Link to comment Share on other sites More sharing options...
Maineah Posted May 13, 2012 Share Posted May 13, 2012 Putting stuff in the cooling system will not fix a head gasket and have a tendency to plug up the heater core. Once upon a time that stuff may have worked on old steel gaskets but any thing modern has a gasket made of many layers of material and basically they rot and come apart when they start to leak. There is a tool used to pressurize the cooling system that connects to the fill port and it has a hand pump to bring the pressure up most any shop will have one. I'm leaning way towards a head gasket but you need to find a shop that can say "yes it is" because it can be expensive. Quote Link to comment Share on other sites More sharing options...
tlava Posted May 13, 2012 Author Share Posted May 13, 2012 Putting stuff in the cooling system will not fix a head gasket and have a tendency to plug up the heater core. Once upon a time that stuff may have worked on old steel gaskets but any thing modern has a gasket made of many layers of material and basically they rot and come apart when they start to leak. There is a tool used to pressurize the cooling system that connects to the fill port and it has a hand pump to bring the pressure up most any shop will have one. I'm leaning way towards a head gasket but you need to find a shop that can say "yes it is" because it can be expensive. Quote Link to comment Share on other sites More sharing options...
tlava Posted May 13, 2012 Author Share Posted May 13, 2012 Actually I just remembered--the shop that put in the radiator, etc, did run a pressure test (along with a compression and leakdown--results noted above; can't recall compression test results, but apparently OK)--but I think I recall them saying that they kept it pressurized for a long period of time, and it was fine? (meaning I guess the system held pressure w/ no problem?); it could be of course that I'm remembering something inaccurately (memory often elides...), or maybe it w as a different type of test? But what you are suggesting is the engine would have to be started once pressurized, to see if it builds up yet more pressure? Putting stuff in the cooling system will not fix a head gasket and have a tendency to plug up the heater core. Once upon a time that stuff may have worked on old steel gaskets but any thing modern has a gasket made of many layers of material and basically they rot and come apart when they start to leak. There is a tool used to pressurize the cooling system that connects to the fill port and it has a hand pump to bring the pressure up most any shop will have one. I'm leaning way towards a head gasket but you need to find a shop that can say "yes it is" because it can be expensive. Quote Link to comment Share on other sites More sharing options...
waiter Posted May 13, 2012 Share Posted May 13, 2012 If the radiator cowl is in place, thats good. The problem is, why isn't the fan clutch engaging, On the test drive, when you see the temp heading toward the red line, pull off the side fast, pop the hood, and check the radiator temp with your hand. If its real hot (can't leave your hand on it), you have a bad fan clutch. If you can leave your hand on it, you have a coolant flow problem. John M Quote Link to comment Share on other sites More sharing options...
Maineah Posted May 13, 2012 Share Posted May 13, 2012 15# vers. 150# the compression is going to win. Yes start it you can leave the gauge at zero but watch the pressure and do not let get too high or it may damage some thing because the pressure tester will not relieve pressure. Quote Link to comment Share on other sites More sharing options...
Maineah Posted May 13, 2012 Share Posted May 13, 2012 The fan clutch is engaged via a bimetal bar the gook inside is very viscus when it's hot and thick when it's cold they will free wheel if there is no air flow even hot the ideal there is noise you should hear it when it locks up they are quite noisy and they do cycle. Usually they fail locked on and make a lot of noise all the time. Quote Link to comment Share on other sites More sharing options...
Totem Posted May 13, 2012 Share Posted May 13, 2012 The fan clutch is engaged via a bimetal bar the gook inside is very viscus when it's hot and thick when it's cold they will free wheel if there is no air flow even hot the ideal there is noise you should hear it when it locks up they are quite noisy and they do cycle. Usually they fail locked on and make a lot of noise all the time. the company i work for engineers and manufactures viscous fan drives. most of this is true; the fluid however is the same viscosity and its the bimetal coil that grows or shrinks with heat also known as the thermostat. the thermostat will open a valve inside the drive allowing the fluid into the "teeth" of the drive; when cool the valve shuts and the fluid spins out slowing the fan speed. Quote Link to comment Share on other sites More sharing options...
tlava Posted May 14, 2012 Author Share Posted May 14, 2012 Sorry--I didn't understand those numbers... BTW--the pressure test I mentioned above (that was done, acc.. to the mechanics) was a cooling system test; also had the engine compression tested. 15# vers. 150# the compression is going to win. Yes start it you can leave the gauge at zero but watch the pressure and do not let get too high or it may damage some thing because the pressure tester will not relieve pressure. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.