L20b overheating. HELP

[WAYBETTER]

So my l20b is overheating. This is a new (used) l20b I just picked up from cali. Spent 3 days putting the motor in. My previous motor was an l18 and did the same exact thing. I have a 3 core radiator with electric fan mount between the rad and grill (always running). Not clutch Fan or fan shroud. Heater core bypassed. No thermostat. New temp sensor. Just driving it around the block for 45 seconds heats up to 3 quarters of the Guage. Both upper and lower hoses are very firm and very very hot. The tstat housing bypass is hooked up as well. Only thing I'm not sure of is that I'm running a W58 head with the non coolant flowing intake manifold but I don't think that would be the issue since my other motor didn't have coolant ports for the manifold on the head. Any ideas?

[datzenmike]

Heater hoses must never be connected together. Yes, this bypasses the core but there isn't a heater valve to shut off the flow. This is hot water that is fed right back into the engine without going through the rad to cool it. If you are connected up this way cut the hose and insert a bolt or anything to block off the flow and gear clamp in place.

 

3/4 gauge reading isn't 'overheating' exactly. I hit 3/4 two days ago climbing a full throttle 20 minute long hill in third gear. It's slightly high but in the 'run range'.

 

With that laundry list of things changed and the same reading, the only common things are the rad and the gauge itself.

 

1/ I suggest borrowing an IR (infra red) gun and 'shooting' the thermostat housing. It should be in the 180-185F range which would be normal. The gauge may be at fault.

 

2/ If higher, take the rad cap off (when cooled and drained) and look at the tops of the coolant tubes. Is there scale present?? It may be three core but if scale is blocking the flow it won't be doing it's job. Lay face up with cap on and fill with CLR to dissolve the scale over night.

 

Always run with a thermostat in place. Engines are designed to give best running/performance/economy and emissions at around 185F.

[Stoffregen Motorsports]

Running hot on the gauge means nothing to me. First off, electrical gauges have so many ways in which they can go bad or give incorrect readings. Bad ground, chewed wire, bad contacts inside the gauge, etc. I almost always run a mechanical gauge. They either work or they break and they don't work, there's never any guessing.

 

There are a few steps in determining if your gauge is in fact working properly. You can remove the temp sending unit and submerse it in a pot of water, bring the water up to a boil and check the readings along the way. You should have the sending unit grounded to the car and the wire hooked up, and it's also a good idea to put a simple meat thermometer in the water during the process. That's one way.

 

Another step to take is to put the meat thermometer in the radiator, with the radiator cap off, and run the engine without the cap until the car heats up. If your thermostat is working properly, you will see the water begin to cycle as it will start to flow across the top tank and you'll also notice stem rising. Check the temp on the meat thermometer against the readings on the gauge along the way.

 

As far as the t-stat goes, you should run one on a street car, but if you really don't want to, you can gut it by cutting out the plunger mechanism and just install the restrictor portion. This way the water doesn't cycle too fast. Removing the t-stat completely is only advisable when it's an emergency and you're trying to get the car off the road.

 

Factory gauges are actually pretty simple to repair, but I bet the fault is somewhere else in the wiring, like a bad ground.

[racerx]

Confirm that ur temp gauge is working properly. How old is your radiator?

[banzai510(hainz)]

why are these heater cores by passed. Another thread ids the same thing. 2 different senders  ect...

 

 

pulling the sender out is risky as most been in for 40 years and mayb crack and then your become friendly with a new guy at the Nisan dealer and say Datsun WHAT? we don't sell Datsuns

 

if the sender housing was on this other motor it cant be bad also. Unless you used the orginal sender housing. howabout swap it out.  as the above write up it was a loose connector on the sender that fixed this.

 

Here is a hailmary GUESS:

a 3 core should not get that hot that fast. unless you got the motor cause the head gasket is bad. If it is bad try pulling the thermos stat on a cool day and run it and if get hot again over time then the motor is leaking hot gas in the the radiator system ,should really blow the cap after awhile I would think

[racerx]

Hainz, hes not running a stat. For it to get too hot in 45 seconds and no stat. Either a bad gauge or sending unit. Or have u done a compression check to rule out bad headgasket? If u do a compression check make sure its operating temp., wide open throttle and dont use plug in type but use screw in type. What about initial timing? Could b retard or belt could b loose.

[LenRobertson]

I'll mention one remote possibility. When I first installed my L20b it would heat up really fast - you would almost watch the gauge climb. It never boiled over cause I would shut it down first.  HRH suggested an air pocket in the thermostat housing next to the temp sender. I thought "That doesn't sound likely". Out of desperation I loosened the top radiator hose at the t-stat housing (engine cold) until coolant leaked out. That solved the problem. If you install a t-stat as everyone suggests, leave the top hose loose when you fill the radiator to be sure it is bled.

 

Len

[DanielC]

If you really mean 45 seconds to show hot, it is not the engine getting hot.  You can run an engine easily for an actual 30 to 45 seconds without any coolant, and it won't make enough heat to overheat.

I think you are having some kind of electrical issue.  Perhaps you have the temp sender wire partially shorted to ground somewhere?

[KoHeartsGPA]

Make that motor burp out the air couple times, a lot of people forget to do this and it is important every time you mess with the cooling system to bleed it.

[Z-train]

Pusher fan is worthless.

[KoHeartsGPA]

I have 2, 9" pushers with a temp sensor on the top of radiator that kicks them in at 175°, it's adjustable from 130° to 190° works really good, the temp drops immediately once they kick in.

[Z-train]

And if you had a 95-ish Taurus fan, you'd be better off. No factory car ever came with pushers.

[datsunaholic]

This is in a what?  510?  Something else?

 

On my 510 the temp gauge would climb quickly when the gauge voltage regulator went bad.  The fuel gauge would also be pegged out at the same time.

[Lockleaf]

A 95 Taurus fan is over 18 inches tall. How many L powered vehicles do you know of that can fit that? Not even sure my 720 could fit it. I know my 510 never could.

 

You are correct that pull is more effective than push for fans. By something like 15 to 20%. not sure how that equals worthless though.

[KoHeartsGPA]

And if you had a 95-ish Taurus fan, you'd be better off. No factory car ever came with pushers.

How so?

 

My setup cools just fine....isn't that the point?

[banzai510(hainz)]

I drill a 1/8 hole in the stat plate. as a bypass if one wasn't installed on the heater line to the manifold.

[datzenmike]

So my l20b is overheating. This is a new (used) l20b I just picked up from cali. Spent 3 days putting the motor in. My previous motor was an l18 and did the same exact thing. I have a 3 core radiator with electric fan mount between the rad and grill (always running). Not clutch Fan or fan shroud. Heater core bypassed. No thermostat. New temp sensor. Just driving it around the block for 45 seconds heats up to 3 quarters of the Guage. Both upper and lower hoses are very firm and very very hot. The tstat housing bypass is hooked up as well. Only thing I'm not sure of is that I'm running a W58 head with the non coolant flowing intake manifold but I don't think that would be the issue since my other motor didn't have coolant ports for the manifold on the head. Any ideas?

 

Impossible to heat that fast! Gauge, or wiring is suspect. Get IR gun and prove it is over heating. 

 

Only commonality with all the things changed including the engine is the gauge and the rad.

 

[Z-train]

A 95 Taurus fan is over 18 inches tall. How many L powered vehicles do you know of that can fit that? Not even sure my 720 could fit it. I know my 510 never could.

 

You are correct that pull is more effective than push for fans. By something like 15 to 20%. not sure how that equals worthless though.

You make it fit.Someone here did.

[KoHeartsGPA]

You make it fit.Someone here did.

No room between my champion and water pump pooley....pushers work just fine....

[datzenmike]

And if you had a 95-ish Taurus fan, you'd be better off. No factory car ever came with pushers.

 

Some Mercedes and I think Volvos do. I have a pusher fan from one of those.

[Lockleaf]

Actually, my s13 came with a pusher fan stock. Granted, it's the secondary fan for when running the a/c, but still, it's a factory pusher.

[scooter]

My pusher fan works good. You have to take note of the curve of the fan blades, if you just take a regular one and put it on the front and run it backwards itll push like shit, turn the fan itself around and run it the proper way itll blow air like a boss

[Stoffregen Motorsports]

I run pusher fans when nothing else will work. Not a problem here!

 

Z-Train is just a grumpy bastard... :thumbup:

[Z-train]

I run pusher fans when nothing else will work. Not a problem here!

 

Z-Train is just a grumpy bastard... :thumbup:

Argh,argh,argh.

 

Simple poser-what works better:

 

A-sucking air thru a semi solid "block"

B-attempting to push air thru a semi-solid "block".

 

This is my sole point.

[datzenmike]

Either will work. Draw through fans are likely quieter because they are behind the rad and why they are used... that and they are less exposed. However consider this...

 

On a draw through fan, the maximum air pressure you can possibly get on the front of the rad is 14.7 pounds at sea level. This is if the fan can achieve a near vacuum on the inside. A pusher fan (just like a turbo) has no upper limit. No pusher or draw through electric fan is anywhere near these extremes. A difference in air pressure is all that is needed to move air through a rad. Push or pull it really doesn't matter. Just driving the vehicle is enough to cool it without the fan on. My old Sundance rarely ever came on. Only prolonged idling would do it.