Stupid_fast Posted January 12, 2012 Report Share Posted January 12, 2012 Well, I've finally decided to create a thread on this... While driving, the temperature will keep going up and up... the faster I go the higher the temp, I always shut it off before it gets past 220. Temps verified with infrared sensor. setup; Everything has ~3500 miles on it. L20b(rebuild), 32/36, fiero radiator, 12" electric fan 350cfm, autometer electric temp gauge. things I replaced since I noticed the overheat; Water pump, upgrade to electric fan, thermostat(tested on stove), head gasket, radiator, ect. I also rewired the gauge ground. While doing the head gasket I visualy inspected everything... I looked into the engine and didnt see any blockage, ect .. old head gasket was fine. I rechecked the cam timing and chain(dropped the tensioner, LOL!) it is set correctly, dizzy shaft 11:28's @ TDC. Comp is good, runs great, fast, good power, goes up hills without a problem. The car has always ran cool before this, 150* driving around on the freeway 70mph, never exceeded 180* sitting in traffic for 15-20 minutes at toll gates, driving to JCCS going 70mph 3500rpm highway 5 like 85-90 deg ambients it topped 170 deg!! Spirited driving on backroads with high throttle would be fine... 3000-4000 constant revvs at lower speeds temps where ~160-170. I've upped the jet sizes on the carb since I drove to JCCS... plugs are light grey suggesting slightly lean. timing set to 12BTDC(timing light) currently and running strong.(I shut off and caost when the temp starts going high) Last time I drove it before it overheated; I drove about 90 miles to see a friend, when I got there driving around town it was performing terribly ... stuttering, popping, stalling ... before I left to come home I found advancing the timing fixed this(to like 25btdc... it before it was timed correctly to 12) Drove home without an issue... 3500 revvs all the way. Temps where fine, I always have a habit of checking them periodicity. 150*-160* there and back freeway temp. Next time I drove it was a few days later, coming home I noticed the temps going up. coasted down the hill to my house and started the last few weeks of troubleshooting. Running observations; Upper radiator hose is HOT when the car is warmed up, lower rad hose is WARM. rad fins where the fan isnt blowing are hot. radiator level is full. radiator cap is good. nothing going into the overflow can. With temp gauge at 180* IR sensor says: block temp 180-200 head temp ~190 upper rad hose 130 lower rad hose 100 temps climb as water temp does... Ideas? Help me ratsun, you are my only (cheap) hope~! Next step is to tow it to Ermish racing and see if he can sort it out. Quote Link to comment
Guest 510kamikazifreak Posted January 12, 2012 Report Share Posted January 12, 2012 Clogged rad? Did you drill the t-stat(fail safe)? Break in period? Is the fan pusher or puller(and is it facing the direction in which it should) The temp sensor is it good?( the fan sensor) Quote Link to comment
wayno Posted January 12, 2012 Report Share Posted January 12, 2012 Did you clean up the engine bay? Did you remove that hose that goes from the bottom of the thermostat housing to the line between the water pump housing(near the lower radiator connection to the water pump) under the mech. fuel pump that goes to the intake manifold? Did you remove this hose also? Are you using an L16 thermostat housing? Quote Link to comment
Stupid_fast Posted January 12, 2012 Author Report Share Posted January 12, 2012 Clogged rad? Did you drill the t-stat(fail safe)? Break in period? Is the fan pusher or puller(and is it facing the direction in which it should) The temp sensor is it good?( the fan sensor) I covered all of this stuff in my post. Yes to all. Radiator is NEW(I put it in yesterday with fresh coolant) straight out of the box... t-stat already has a little failsafe/jiggle valve. I tried running motor without thermostat didn't make a difference. Already broke in the engine just fine, comp is nice at 170/cyl. over 3000 miles since break-in run and 5 oil changes later w/ K&N filters... valvoline non-synthetic VR-1 30w for break-in run and now 10w30 .. Fan is the correct way around, hooked up as a pusher. Fan is hooked up to be on when IGN is on w/relay(temporary solution). Did you clean up the engine bay? Did you remove that hose that goes from the bottom of the thermostat housing to the line between the water pump housing(near the lower radiator connection to the water pump) under the mech. fuel pump that goes to the intake manifold? Did you remove this hose also? Are you using an L16 thermostat housing? Bay was cleaned before I dropped the engine in. There is no hose to the bottom t-stat housing(L16 stuff). The head has no water ports. I want to drive it!! Quote Link to comment
Laecaon Posted January 12, 2012 Report Share Posted January 12, 2012 Get it up to temp with Rad cap off, this lets you check for flow, though Im not sure what to see on a fiero rad... Quote Link to comment
Stupid_fast Posted January 12, 2012 Author Report Share Posted January 12, 2012 Get it up to temp with Rad cap off, this lets you check for flow, though Im not sure what to see on a fiero rad... With rad cap off, revv it and coolant level drops down low, revv it hard and can see coolant spilling from the rad core... Radiator gets warm meaning there is flow and heat transfer... fins where the fan is blowing are cold. Quote Link to comment
wayno Posted January 12, 2012 Report Share Posted January 12, 2012 I ran a L16 thermostat housing on my LZ23, my water temp was all over the place, uncontrolable, it would be just fine for days, then go crazy and overheat, even though the gauge did not show it being that high of a temp, the water jacket did not flow correctly without the bypass hose, I put the bypass hose back in, with the L20b thermostat housing, and have not had any issue with the water temp since. Quote Link to comment
Stupid_fast Posted January 12, 2012 Author Report Share Posted January 12, 2012 I ran a L16 thermostat housing on my LZ23, my water temp was all over the place, uncontrolable, it would be just fine for days, then go crazy and overheat, even though the gauge did not show it being that high of a temp, the water jacket did not flow correctly without the bypass hose, I put the bypass hose back in, with the L20b thermostat housing, and have not had any issue with the water temp since. What. If you are sure that will fix my problem... Time to replace the t-stat housing. I have an L20b housing but the bypass was plugged when I got it. Its where I installed the auto meter temp sender... with the wrong fitting and busted up the lower housing. I have it JB-welded in at the moment. So run it from the lower t-stat housing to the water inlet port next to the lower rad hose? Quote Link to comment
Laecaon Posted January 12, 2012 Report Share Posted January 12, 2012 Yes, on the water inlet there is a small stem that points directly up. That is where it goes. Quote Link to comment
Stupid_fast Posted January 12, 2012 Author Report Share Posted January 12, 2012 Yes, on the water inlet there is a small stem that points directly up. That is where it goes. OK.. I'll try to go to hardware store and rig something up replacing the stock temp sender..(stock gauge does not work anyway) Such a bizarre problem... It makes no sense to me that this would fix it. Quote Link to comment
Laecaon Posted January 12, 2012 Report Share Posted January 12, 2012 Yea, I dont really think it would either with you having ran it without the thermostat... Quote Link to comment
ggzilla Posted January 12, 2012 Report Share Posted January 12, 2012 Temp sender is not the problem if you verified 220 degrees with an infrared. I'm going to guess it is that tiny electric fan. Although L20B wants a good return hose from the thermostat housing. It could be that. Quote Link to comment
wayno Posted January 12, 2012 Report Share Posted January 12, 2012 The hose starts at that tube pointed strait up above the lower radiator hose connetion to the water pump. Then it goes forward and turns in front of the head towards the distributor. Then it comes to a tee, the top of the tee goes to the thermostat housing, and then the line continues to the intake manifold. This is a photo of how that thermostat line connects to my thermostat housing, see the small brass fitting with the small hose connected to it under the upper radiator hose connection. I am not saying this will fix your issue, as I can only suggest avenues to take based on the info you have supplied, when I had an L16 T-housing with no bypass hose, I had overheating issues just appear out of nowhere. Quote Link to comment
wayno Posted January 12, 2012 Report Share Posted January 12, 2012 I am baffled that you had the same issues without a thermostat though, seems like it wouldn't even get to operating temp, when it was out, could you see the water actively flowing while the engine was running? Is your lower radiator hose kinked any, when you rev the engine, does it look like it is getting sucked flat? Quote Link to comment
EricJB Posted January 12, 2012 Report Share Posted January 12, 2012 What kind of carb? Plugged or still undersize jetting? Are you sure the vacuam and mechanical advance are working? What is the total advance? Initial timing is for start up and you need to know where it's at while driving. Retarded timing will send the exhaust temps thruogh the roof. If you are driving at any where near hiway speed, the fan should never cycle. As stated earlier, are you sure the fan is drawing air though the rad towards the engine? Take it to an onramp and kill the fan, then roll at 60mph and see what happens. Cooling fans are for traffic.My .02 Quote Link to comment
Stupid_fast Posted January 12, 2012 Author Report Share Posted January 12, 2012 Sigh I'm an idiot... I just bled the system(method on datsun 1200 wiki) and it works fine now. temps on backroad/giving throttle 2500-3500rpm's are 160-170... just under 180 idling in the garage. Maybe the coolant bypass prevents air from getting trapped? I feel like a complete idiot now... thank you all for the help. What kind of carb? Plugged or still undersize jetting? Are you sure the vacuam and mechanical advance are working? What is the total advance? Initial timing is for start up and you need to know where it's at while driving. Retarded timing will send the exhaust temps thruogh the roof. If you are driving at any where near hiway speed, the fan should never cycle. As stated earlier, are you sure the fan is drawing air though the rad towards the engine? Take it to an onramp and kill the fan, then roll at 60mph and see what happens. Cooling fans are for traffic.My .02 weber 32/36 .. might still be underjetted, but its running OK now. It never overheated when it had even smaller jets. Vac adv not sure if working... will troubleshoot that, at 1k RPM's it likes around 20btdc ... unsure why that is still. Yeah, I'm going to wire up a switch for the cooling fan.. this was just a temporary solution. Quote Link to comment
ggzilla Posted January 12, 2012 Report Share Posted January 12, 2012 Glad to hear another Datsun fixed! at 1k RPM's it likes around 20btdc ... unsure why that is still Gasoline engines like lots of advance at part throttle. That's why vacuum advance is used. If you set it to 20 degrees static at 1,000 RPM, at full throttle it may damage the engine. Instead set it to 10 degrees at 700 RPM and let the vacuum advance pull it to 20+ degrees. VA drops to 0 at full throttle so it won't over-advance the engine. Read Spark Curve for more information. Quote Link to comment
Stupid_fast Posted January 12, 2012 Author Report Share Posted January 12, 2012 Glad to hear another Datsun fixed! Gasoline engines like lots of advance at part throttle. That's why vacuum advance is used. If you set it to 20 degrees static at 1,000 RPM, at full throttle it may damage the engine. Instead set it to 10 degrees at 700 RPM and let the vacuum advance pull it to 20+ degrees. VA drops to 0 at full throttle so it won't over-advance the engine. I see... its normal to run a bit rough with 12btdc? 32/36 carb.. Gonna go fill up the gas and take it for a spin... Quote Link to comment
ggzilla Posted January 13, 2012 Report Share Posted January 13, 2012 Not normal to run "rough", but it is normal to run smoother with more advance. Depends on what you mean by "bit rough". If you change the timing, reset the idle speed and mixture. They should be set below 800 RPM. Weber 32/36 should idle every bit as smooth as the stock carburetor. Quote Link to comment
banzai510(hainz) Posted January 13, 2012 Report Share Posted January 13, 2012 Fan is the correct way around, hooked up as a PUSHER?????????? Well hope it means take cooler air in and blow on engine. Or you mean fan is on outside of the rad. Than inside. Maybe the coolant bypass prevents air from getting trapped? Use the stock bypass system or drill the top of the stat 1/8 hole. Quote Link to comment
Guest 510kamikazifreak Posted January 13, 2012 Report Share Posted January 13, 2012 Sigh I'm an idiot... I just bled the system(method on datsun 1200 wiki) and it works fine now. temps on backroad/giving throttle 2500-3500rpm's are 160-170... just under 180 idling in the garage. Maybe the coolant bypass prevents air from getting trapped? I feel like a complete idiot now... thank you all for the help. weber 32/36 .. might still be underjetted, but its running OK now. It never overheated when it had even smaller jets. Vac adv not sure if working... will troubleshoot that, at 1k RPM's it likes around 20btdc ... unsure why that is still. Yeah, I'm going to wire up a switch for the cooling fan.. this was just a temporary solution. Hmm wasnt this one of the first things I suggested in status :lol: Glad it worked out :cool: Quote Link to comment
datzenmike Posted January 13, 2012 Report Share Posted January 13, 2012 Maybe the coolant bypass prevents air from getting trapped? Not really as it just goes down to the lower rad inlet anyway. Notice that the thermostat housing is on the side of the head? Well when the motor warms up, if the thermostat is closed how does the hot water get to the thermostat to make it open???? Well the short answer is it won't. Heat would have to slowly warm the water by convection and meanwhile the hottest part of the motor will over heat. The by pass hose allows a small amount of water to circulate around in a loop from the head back down to the lower rad hose inlet to the water pump. Because water is circulating past the thermostat it samples the temperature and opens as soon as needed. Without the bypass the engine will have a heat spike, may even boil over but the gauge will read low. Vac adv not sure if working... will troubleshoot that, at 1k RPM's it likes around 20btdc ... unsure why that is still. Vacuum advance not connected. Unless off to show the by pass hose. Take dizzy cap off, suck on hose going to dizzy, rotor should turn clockwise. Place tongue over end of hose, rotor should not return until you let go. Quote Link to comment
ggzilla Posted January 13, 2012 Report Share Posted January 13, 2012 overheating problem already fixed ... Quote Link to comment
banzai510(hainz) Posted January 13, 2012 Report Share Posted January 13, 2012 I tried running motor without thermostat didn't make a difference This part got me confused!!!!!!!! It should have ran cold Quote Link to comment
datzenmike Posted January 13, 2012 Report Share Posted January 13, 2012 overheating problem already fixed ... Yes, that was to address the two quotes about th by-pass and vac advance. Quote Link to comment
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