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Leo92335

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With the engine thoroughly warmed up and idling the thermostat should be slightly open. It should have a 180-185F thermostat. An infra red gun should read near this. Certainly enough to tell weather the stock gauge is wrong. On my 620 the gauge reads about a needle width past 1/2. It's the same on my 710's L20B. The electric fans come on at about 2/3 and I have an IR gun that I should shoot these for some hard numbers.

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Hey buddy thanks for the reply,the aftermarket sensor is located between the radiator and the thermostat housing in the hose,its a 3 in 1 electronic digital display that goes on top the dashboard with alarm sounds for low battery, temperature and oil pressure pretty neat device,,I would like the readings of the top of your thermostat housing, the radiator,top and bottom radiator hoses, I'd really appreciate your help 

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4 hours ago, Leo92335 said:

Hey buddy thanks for the reply,the aftermarket sensor is located between the radiator and the thermostat housing in the hose,its a 3 in 1 electronic digital display that goes on top the dashboard with alarm sounds for low battery, temperature and oil pressure pretty neat device,,I would like the readings of the top of your thermostat housing, the radiator,top and bottom radiator hoses, I'd really appreciate your help 

Ok I'll have to get a few more readings ....

I am running a 180 thermostat,  and I basically had 180/185 at the thermostat....

I think my thermostat top is a cast iron part vs the lower being aluminum so I'm not sure how much that effects things....

 

Going to go back outside now to warm the truck up and write down the numbers in those spots for you....

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So these number may or may not be good, I think my ir gun just died.... 

It started to give me some error code and high limit reading ... then it seemed to be acting ok.... wish i had a way to check calibration on it....

I really need to update my tools....

..... 

Anyhow the gauge on my dash was pointing right at the center line and these were the readings I got....

 

The top of the housing got to 175

What was surprising to me was the top hose was only 145.... 

The radiator was around 125 and the lower hose was around 105..... 

 

I'll check once more after I drive to work tomorrow to see if there is any variance... 

These numbers were after my truck cooled down, then with the hood open I started it back up till it warmed up ...

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Fully warmed up 185 on the top of the thermostat housing and top rad hose and just above 1/2 on the gauge. If left idling it climbs to 195  at 2/3 and fans come on. Within 10 seconds they turn off and it's another 30 seconds before they come on again. 

 

I'm going to do this again tomorrow, I got some really goofy numbers. Going to shoot the thermal switch that turns the fans on and see what it's set at.

 

Oil temp is 176 but the highest I ever got it was 93C or 199F

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14 hours ago, Leo92335 said:

Thank you for the readings ,I'll compare them to my truck fully warmed, and if you could send the second readings will be awesome, 

So no real difference in my numbers ... it was about 70 out this morning driving into work.... I checked it the minute I parked while it was still running....

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17 hours ago, datzenmike said:

Fully warmed up 185 on the top of the thermostat housing and top rad hose and just above 1/2 on the gauge. If left idling it climbs to 195  at 2/3 and fans come on. Within 10 seconds they turn off and it's another 30 seconds before they come on again. 

 

I'm going to do this again tomorrow, I got some really goofy numbers. Going to shoot the thermal switch that turns the fans on and see what it's set at.

 

Oil temp is 176 but the highest I ever got it was 93C or 199F

Thank you for your help I really appreciate it 

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3 hours ago, Crashtd420 said:

So no real difference in my numbers ... it was about 70 out this morning driving into work.... I checked it the minute I parked while it was still running....

Thank you very much, I really appreciate it, ill check it out and ill go from there 

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On 6/18/2020 at 5:45 PM, Leo92335 said:

I'm new to this forum and I don't know how to load the pictures, when I try to load pictures it asks for the url address and I can't seem to find the upload from my phone option 

Use Postimage.org

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Ok fellas I'm going crazy with this truck, I installed a thermal switch that starts the fans at 185 and stops at 175 ,and when idling seems to stay around 185 after a 5 minutes warmed up and a 5 minutes drive my dash gauge went to fully hot and my digital gauge went to 208 ,I just filled it with yellow antifreeze, has new sparkplugs,new sparplugs cables ,I  timed it to 10 degrees ,i installed a Webber carb,I I installed 2 push fans 10 and 8 inches that cover all the radiator,it has a new aluminum radiator, new thermostat housing with new thermostat sensor ,seemed like a new 180 thermostat ,,the  engine it self sounds and runs great its very steady and powerful ,I don't see any physical problem except my gauges are telling me its overheating ,,,and I've noticed my dash gauge goes from 3/4 hot to full hot with a couple of tire turns on my driveway and also when its reads super hot and I turn off the engine than i start the engine again it goes back to 3/4 or around 60% hot so I'm suspicious that my dash gauge is defective ,the 3 in 1 digital gauge i installed it's at the top radiator hose with its own temperature sensor is a $25 kit from china so I don't know if it's accurate and that one also reads 208 when supposedly super hot,,,,  i cleaned my heater core and its good but I've noticed one of the metal elbow its leaking so I'm just gonna eliminate and bypass that heater switch ,also my differential is leaking oil,,  my temperature readings when parked and idle are thermostat housing 145,radiator 185 ,valve cover engine 145,top hose 171 bottom hose 160 ,,,,can some one helped me try to figure it out what's wrong with this truck if it's my gauges or its something that when I start driving it overheats 

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Would you say that it can sit and idle without over heating? The fans come on but the gauges seem to read ok??? Would it be fair to say that???

 

What happens if it's idling in the driveway and everything is fine and you rev it up to a fast idle and hold it there?

 

 

Does your gas gauge change readings too, like at 3/4 but goes up to full when driving?

 

 

 

If you by pass the heater core, be sure to block any flow from the head to the lower rad hose fitting on the timing cover. Hose ends must be plugged off.

 

 

 

 

 

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Hello Mike, thanks for the reply,yes it idles with out overheating, yes when the fans turn on the gauges are ok and steady, the digital stays about 180-185 and the dash little bit after the half mark about 65% ,yes it stays the same readings if I rev up at 3000 for one minute ,yes my fuel gauge is acting up sometimes when I'm driving ,it shows full when it only has about half of tank,,,,,,idling at 850 rpms it took the fans about 11 minutes to turn on at around 185 and they turned off 30 seconds later ,

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 The temperature and the gas gauges have something in common. Both run on 8v from a common voltage regulator. The voltage system on a truck can be from engine off... 12.6 (often less) to 14.5v when revved up. As you can see the gauge would vary if this was the case. To get around this a steady 8v supply is provided so they remain accurate no matter what.

Usually the regulator points get dirty and both gauges fail to work. Cleaning with sand paper usually get them going again.

 

 

In this case It seems there is no steady 8v and they are running on something that varies causing the high readings. This is why the temp gauge pegs as soon as revved up driving.

 

 

Ova4dr0.jpg

 

 

Are you up for an experiment?

 

If you pull the two wire plastic plug out of the back of your alternator it will disconnect from the electrical system.  You can still start and drive it on what's stored in the battery. Try taking for a drive and see if your gauges remain stable.

 

Check out that digital gauge too. Does it now also read 185-ish instead of over 200????

 

 

 

I'm thinking that you may be over charging

 

 

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11 hours ago, datzenmike said:

I'm thinking the charging system may be higher than the usual 14v. Might be 18 or something and why the new digital gauge reads 203F

This is definitely worth checking....

 

Leo you have pretty much the same coolant setup as me... you should be good, I know your not but the you should be....

If it's not voltage then really the only 2 things left would be a failing water pump and then worse case the head gasket is starting to go.... 

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I would expect one of two things if the head gasket were going bad.

 

Coolant drawn into the cylinder. You may not notice the steamy exhaust in the summer and if in small enough amoubts it might not get past the rings and make the oil chocolaty but you can't miss the constant topping up of the radiator from mystery coolant loss

 

Compression forcing it's way into the cooling system. This will over pressurize the system and expel coolant out the rad overflow hose. Again noticeable loss of coolant.

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Hey Mike,banzai and others I hope you guys having a great day  ,I fixed the dash temperature gauge problem it was a bad ground, I went for a drive and took it on the freeway and did not pass the middle on a semi-hot day so I'm assuming it will not overheat anymore, thanks for all your help guys,,,,,but unfortunately I'm not done with my issues i think I have a bad head gasket, I have a bad rear pinion seal,my starter clicks a lot of times and it starts after a few tries, I have a new battery,new ignition switch and new starter, what do you suggest I do to fix my ticking starter?

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Check the battery ground cable where it bolts to the head is clean and tight. Check the battery positive cable is well connected to the starter lug.

 

Still nothing???

 

Make a long enough wire an jumper 12v directly from the starter to the small terminal on the starter solenoid. Make sure you are out of gear and the brake on. Might not hurt to have the coil wire off too. Does this turn the starter properly now every time you touch the terminal

 

Yes the starter operated properly. The start signal from the ignition is weak. Look up "hot start relay" on line and make or buy one.

 

No, the starter still clicks and chatters. The starter solenoid is probably bad. You can change it without taking the starter out.

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The starter cranks everytime I jump the battery positive connection and switch cable so I will get a relay, I found a video where they teach how to wire the relay,,thank you ,have you ever replace a rear axle pinion seal?,I've never done it and i already watched a bunch of utube videos about it but they are all different from a datsun 

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Both my 710 have a hot start relay. My old sedan was 3 or 4 tries befor the starter would properly turn the engine and start. I had about a dozen starters so I just swapped one in but it kept doing the same. I measured the start signal and it was 7-8v!!! 

 

I have on a truck and was lucky it worked fine.  To get at the seal the pinion nut has to come off and it has a crush sleeve and select shims for the ring and pinion settings and I was afraid I would disturb everything. I carefully pried the old seal out and  tapped the new one in and tightened the nut on as tight as I could.

 

The 620 is a third member style differential. This is for a Toyota but I bet it's close...

 

 

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Thanks for the video Mike, I'm sure it will help, about my suspicion on the bad head gasket when I start the truck and its cold not alot of smog comes out but when the thermostat opens it starts smoking a lot like visible during day,,,I will start driving it to work so I can check the coolant but just with the heavy smoking I think it's bad 

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