240Z Overheats in traffic and low speeds (New radiator, thermostat)

[Connor280ZX]

Welp, here's the deal. Bought my 240Z with 6 holes in the original radiator, and replaced it with a two row aluminum radiator that i bought off of Ebay new after i got the car running.

 

First, here's the description of the engine:

-L24/E31

-3 screw S.U carbs

-Unknown cam (P.O says it's a Crane Cam, but he's not sure)

-Header-back twice pipes

-180F Thermostat (Here in Norcal, climate is humid, 50-75F normally)

-Roughly 25/75 Antifreeze/Coolant mix.

 

With that stated, I've started driving the car now and basically it does what i've stated in the title. Get up to cruising speed, the needle stays around the middle mark.

When i slow down (Lets say under 20MPH) the needle starts to creep up quickly, and rest around 220-230F. If i stop, the needle pegs at the redline on the temp gauge, very scary. I get going again slowly, being very gentle with the throttle since i don't want to blow the head gasket, and the temp will slowly lower back to normal.

 

One day when the temp gauge wasnt working, i got caught in heavy traffic... I'm sure the engine got very hot because even after getting up to speed for a few minutes, i pulled into my garage and steam started spewing from the overflow line... I checked the oil, and luckily it was clean. No water in the oil. Phew...

 

A few things to note: Heater lines are blocked off. Manifold coolant lines are disconnected.

Ignition timing is at 0 BTDC. Coolant level is about 1.5 inches from the cap.

 

Oh, and the P.O Ran straight water in the system... Had to replace the water pump inlet because it dissolved due to this.

 

I'm thinking it could be the fan clutch, but not sure.

Edited June 14, 2014 by Connor280ZX

[Domzs]

Sounds like a fan clutch problem . Normally , you don't need the fan above 25 mph . Look at your fan at idle with high engine temp. and should feel heat coming through .

[TimZ]

Ignition timing is at 0 BTDC. Coolant level is about 1.5 inches from the cap.

 

 

Is that the correct ignition timing for the L24?  I thought the initial timing was more like 10-15 degrees.  Retarded initial timing could cause the symptoms you describe...

[Connor280ZX]

Is that the correct ignition timing for the L24?  I thought the initial timing was more like 10-15 degrees.  Retarded initial timing could cause the symptoms you describe...

The user's manual says 5 Deg, but i have advanced the timing as far as the distributor will turn.

 

Sounds like a fan clutch problem . Normally , you don't need the fan above 25 mph . Look at your fan at idle with high engine temp. and should feel heat coming through .

That could be the problem. I guess the fan should spin faster at low RPM, but i'll have to check to see how it is working the next time it overheats. Honestly, i fear blowing something if i get it hot again... The fan pulley does wobble for some reason though. Not sure if that has to do with anything.

[NorwegianZED]

If I am not mistaken, I seem to remember the fan pulley and fan being attached to the waterpump. If it wobbles and overheats I would check my waterpump also. There should be a hole in the waterpump that will release water if the pump is broken/worn.

Has it lost any water?

[Nigel]

Bad fan clutch, retarded timing and failing water pump are all good possibilities. Regarding the fan clutch, it's typically not an obvious failure. With the engine running, you'll see the fan spinning away and think that everything is fine with it. But it will actually be moving very little air. With the engine off, rotate the fan by hand. It should feel quite stiff. If it's easy to turn, replace the clutch. After you replace it, you'll suddenly notice that it sounds like there's a jet engine under the hood.

 

Nigel

[Six_Shooter]

The user's manual says 5 Deg, but i have advanced the timing as far as the distributor will turn.

 

Where you have it set would be retarded. The 5 degree spec is an advanced or BTDC (Before Top Dead Center) measurement. Setting the base timing to 0 degrees is 5 degrees retarded from the spec.Also when you set it, did you disconnect the vacuum advance, if you did not then the actual base timing is even more retarded than that.

[Connor280ZX]

If I am not mistaken, I seem to remember the fan pulley and fan being attached to the waterpump. If it wobbles and overheats I would check my waterpump also. There should be a hole in the waterpump that will release water if the pump is broken/worn.

Has it lost any water?

Loosing coolant, yes it was. However, my bottom radiator hose was not tightened down competley, so there was a small trickle coming out. Other than that, i'm really not sure. Next time i drive it, i'll check the level before and after the drive to see if its still loosing coolant.

 

 

 Regarding the fan clutch, it's typically not an obvious failure. With the engine running, you'll see the fan spinning away and think that everything is fine with it. But it will actually be moving very little air. With the engine off, rotate the fan by hand. It should feel quite stiff. If it's easy to turn, replace the clutch.

 

Nigel

Yes, its very easy to turn when the engine is off. If i can get it to spin with my hand almost freely actually.

 

 

Where you have it set would be retarded. The 5 degree spec is an advanced or BTDC (Before Top Dead Center) measurement. Setting the base timing to 0 degrees is 5 degrees retarded from the spec.Also when you set it, did you disconnect the vacuum advance, if you did not then the actual base timing is even more retarded than that.

I did disconnect the vac advance. Timing the ignition for me seemed a little tricky since those groves in the crank pully arent highlighted. The little arrow was pointing slighty above the bottom groove on the pulley.

[Six_Shooter]

Ok, that sounds like the procedure, but at 0 degrees, the timing is retarded from where it should be, if the spec is 5 degrees, not advanced.

If you're saying that turning the dizzy as far as it will go will only get you to 0 degrees and not 5 degrees BTDC, then you need to find out what is not correctly installed, be it the oil pump drive or the placement of the plug wires on the dizzy cap.

Edited June 14, 2014 by Six_Shooter

[rejracer]

In my experience retarded timing will make the engine run cooler, but the exhaust system much hotter. 

 

If the previous owner ran water in the system, what have you done to clean the system?  Do you know if they used tap water or distilled?  It only takes a few weeks for a new radiator to get mineralized and quit working if installed in a contaminated system.

[Connor280ZX]

In my experience retarded timing will make the engine run cooler, but the exhaust system much hotter. 

 

If the previous owner ran water in the system, what have you done to clean the system?  Do you know if they used tap water or distilled?  It only takes a few weeks for a new radiator to get mineralized and quit working if installed in a contaminated system.

All i have done to clean the system is basically let the water drain out of everything. The heater lines are all disconnected/plugged, so i didnt bother with the heater core. I have no idea what form of water they used in the engine, but whatever they used caused this:

Edited June 15, 2014 by Connor280ZX

[rejracer]

You have a heavily corroded / contaminated system.  Until you fix that, the car will overheat regardless of what radiator, fan or shrouding is on there. 

 

As of now, your block has a lot of rust scale in it, and the aluminum parts are covered in aluminum oxide.  The white stuff in the picture is aluminum oxide.  A surface that is corroded is less efficient at transferring heat than a clean surface. 

 

Products I use to de-corrode and clean a system:

1. Prestone super radiator cleaner

2. evapo-rust

3. Prestone super radiator flush

 

Process:

1. Use the prestone cleaner, follow the directions.  This step cleans the major crud in the system

2. Flush the system using tap water, forward and reverse flush the radiator, block and heater core.  Drain fully

3. Use the evapo-rust with distilled water. This step get rid of the rust in the block and the aluminum oxide in the head and front cover. 

4. Flush the system using tap water, forward and reverse flush the radiator, block and heater core.  Drain fully

5. Use prestone super radiator flush, this step cleans any remaining contaminates in the system. 

6. Flush the system using tap water, forward and reverse flush the radiator, block and heater core.  Drain fully

7. Flush one last time using distilled water, no cleaners. 

8. Once system is clean to satisfaction, fill with desired coolant mix.  I suggest 70% coolant, 30% distilled water.  I use prestone yellow coolant.  Any coolant will work, just don't mix them, (yellow with green) and use only distilled water.  Never use tap water in a cooling system.

 

With a system so heavily corroded, you might find new leaks in the system.  These are problems that would surface anyway, the aggressive cleaning just made the problem visible.  When the metal is dissolved like that on the water inlet, there is heavy corrosion on the inside of the engine as well.  If the corrosion gets too bad, it can ruin a block or head. 

 

Every car I do this on goes from being a basket case to a trouble free system, and stays that way.

[TimZ]

In my experience retarded timing will make the engine run cooler, but the exhaust system much hotter. 

 

If the previous owner ran water in the system, what have you done to clean the system?  Do you know if they used tap water or distilled?  It only takes a few weeks for a new radiator to get mineralized and quit working if installed in a contaminated system.

In my experience it makes both run hotter.  As six_shooter mentioned if you can't get more advance than 0 degrees, then your drive spindle is misaligned.

 

Agree on cleaning the crap out of the system, though.  Do you still have the old radiator laying around?  If so, consider putting it back in during the cleaning/flushing process just to avoid pumping all the crap you're gonna set free during the flush through your shiny new radiator.  Judging from your pic, you're already going to want to backflush the new one, but no need to make it worse if you don't have to.

 

Also - fan pulley wobbling? Seriously? Get to the bottom of that.  Disaster waiting to happen.

 

So far I would say that ALL of the things suggested need to be addressed, and you will continue to have problems if you try to pick and choose hoping for the silver bullet.

[Six_Shooter]

In my experience it makes both run hotter. 

 

 

 

Same here, and that goes for several cars.

 

In my 240 I was able to drop average engine running temp by 10 degrees by advancing the timing in the common load areas. This just showed that the timing was far too retarded to start with.

[Connor280ZX]

You have a heavily corroded / contaminated system.  Until you fix that, the car will overheat regardless of what radiator, fan or shrouding is on there. 

 

As of now, your block has a lot of rust scale in it, and the aluminum parts are covered in aluminum oxide.  The white stuff in the picture is aluminum oxide.  A surface that is corroded is less efficient at transferring heat than a clean surface. 

 

Oh great, i had a feeling... I hope i haven't done too much damage to my new Rad, probably have less than 30 miles on it. I'm sending the car in tomorrow to get brake work done, could i trust the shop to perform this whole cooling system flush procedure while the car is there?

[rejracer]

Depends on the shop, but most shops I would not trust to understand what's going on inside.  It will be labor intensive.  Either invest the time and a few dollars doing it yourself, or a lot of money to have someone else do it.  If you decide to do it yourself, have the shop drain the coolant from the entire system.  All the chemicals used are environmentally safe, so disposal is easy.  The cleaners to do this are less that 50$, but the labor should be in the ball park of 3-400 if the shop intends to do a good job an still make a bit of money. 

 

A few weeks will not permanently hurt the radiator.  Once it goes through the cleaning cycles it will be fine.  It's not rocket science, just basic chemistry.

[Connor280ZX]

 

3. Use the evapo-rust with distilled water. This step get rid of the rust in the block and the aluminum oxide in the head and front cover. 

4. Flush the system using tap water, forward and reverse flush the radiator, block and heater core.  Drain fully

5. Use prestone super radiator flush, this step cleans any remaining contaminates in the system. 

 

With the distilled water in the system, of course im going to have to fill it up and run the engine to get it circulating since this stuff doesnt come out of a garden hose. But how long should i run the engine before i empty the system again? Untill it warms up?

[rejracer]

You run each cleaner for the time specified on the label of the product.  From memory: the 1st cleaner you run for so many miles.  Let the engine cool then do the garden hose flush.  The evapo rust you leave in for a couple of hours at full operating temp.  The last flush you run for around 15 minutes. 

 

Basically follow the directions on the labels of each cleaning product. 

 

When flushing I drain it right after i shut it off, then let it cool, and fill it back up with whatever the next step calls for.  Don't add cold water to a hot and empty engine. 

 

In all of this each time I drain the system, I catch the liquid in a drain pan and take note of the debris coming out.  The evapo rust I reuse, so I will filter it and run it again if I think the system is still contaminated.  The evapo rust if it's not fully neturalized by running it through the engine will continue to work for a week or so. 

 

The other cleaners are done for after the time on the labels, I still catch the product, but mostly to analyze what's coming out.  At each step if im not comfortable with what is coming out, or I think the system is still dirty, i'll redo the step.

 

Don't get too engrossed in the details, the goal here is to just remove any sledge, corrosion. minerals and any acidic conditions that will cause further problems.  The steps provided are a fairly robust way of doing that.  Take a good look at the system after each step to determine your next steps.  You might get away with just the first step, or you might have to repeat each step multiple times.  It all depends on how bad your system is. 

[rejracer]

I wanted to add why a corroded coolant system is so hard on an engine.  The heat generated in a combustion chamber needs to flow through the metal into the coolant, then from the coolant into the radiator, then from the radiator into the air.  There are 3 heat exchanges going on.  When your car is overheating, and you have sufficient airflow through the radiator, and your water pump & thermostat is working then the temp your engine is running at is actually higher than what the coolant is. 

 

The reason for this is the corrosion that prevents heat transfer is on the inside of the engine as well as the radiator.  So if your coolant is running 50* higher than you expect, it's safe to assume the temps your engine is running at is 100* higher.  If the heat cannot get from the engine into the coolant there will be a significant temperature difference.  I don't know if the temp difference is a 1:1 ratio or not.  I suppose it's dependent on how bad it is and if it's rust or minerals, regardless it IS something, and I would bet it's close to the 1:1 ratio.  In other words if coolant temp is 50* hot then your engine is actually 50* over coolant temp.

 

A engine overheating due to a corroded coolant system is far worse than an engine overheating due to insufficient air flow through the radiator. 

 

If you wanted to measure how much of a difference this is making, it could be done via a cylinder head temp sensor if your car is equipped.  I've never checked it, but with a new ecu and the ability to log it, i think I might do that one of these years...

 

Make sense? 

[Connor280ZX]

Wow. That's interesting, and kind if scary too. I did peg the temp gauge once coming home. I started the cleaner process yesterday. However the head gasket blew today while driving around. #3 and #4 hydrolocked with water and oil. Oil is white now. So screw it! Time for an L28 swap. I'll make a post now that my engine Is for sale. Still runs, but only on 4 cyl.