Overheating That Z-Car? I have read about a million people on forums ask how to solve their overheating problems. Every time I see someone with overheating problems I imagine them letting it go another day 'til they burn the engine. Hopefully the following will help.
I have heard everything from,"It overheats right away," to "It overheats only when you're doing 75 on the freeway." I will explain a good order for fixing things starting with the easiest and cheapest and going to the more extensive and expensive. I will also explain what symptoms these fixes can solve.
Most cars die by reaching the 1,000,000 mile mark (over exagerated for effect) or by overheating due to lack of coolant or oil. If a hose busts while on the freeway, the engine can die instantly. The following steps are vital to ensure that your cooling system operates effectively. Make sure that your oil level is always within the cars specification.
Now for the fixes. I have an '84 Z that was overheating. I had problems with high temps driving around town, but freeway driving was the best test. I thought the timing was off so I replaced the timing belt (needed to do it anyway and I got it done for only $100, with OEM Belt). Timing wasn't my problem. I hit the freeway and the temp. soared like before. Is this you?...I replaced the t-stat, the radiator cap, the hoses, the water pump, and flushed the cooling system out a couple times. I had it pressure tested and diagnosed. Well if this is you...go through this list and then see if you still have problems.
These are problems that can cause overheating:
• Coolant level low
• Improper fan operation
• Radiator hose(s) collapsed
• Radiator airflow blocked
• Faulty pressure cap
• Ignition timing incorrect
• Air trapped in cooling system
• Heavy traffic driving
• Incorrect cooling system components
• Faulty thermostat
• Water pump shaft broken or impeller loose
• Radiator tubes clogged
• Casting flash in cooling passages (who knows what this is)
• Brakes dragging
• Excessive engine friction (worst case scenario)
• Antifreeze concentration too high (over 68%) Missing air seals
• Faulty gauge or sending unit (read high but not really overheating). A Gauge can read low so it's important to maintain and efficient cooling system.
• Loss of coolant flow caused by leakage, foaming, or obstruction in cooling components
• Viscous fan drive failed
• Bad head gasket or cracked head (should be obvious by lack of power and leakage from head when pressure checked...very worst case scenario.)There may be many more things that can cause overheating, like going uphill really fast, or towing, but we'll allow you to figure them out as you are the one using the car. A couple other ideas are presented below. The order of fixing and what symptoms they might take care of. A few of these are preventive measures that should be executed weekly. If you notice any overheating or loss of coolant...
1) Make sure the coolant level is just under the radiator cap level. If it isn't this could solve any overheating problems you have right off. Just top it off (with 50-50 mixture water-coolant) and check the overflow reservoir. This should be done if when the car is cold. After running the car the reservoir level is higher than when the car is cold because the coolant expands when hot. If the reservoir is ever empty, it should show up on your display panel.
Note: Water cools better than antifreeze...but generally a 50-50 mix of water to antifreeze is good.
In cold weather 40-60 (water-antifreeze) is suggested.
2) Visually check the hoses for wear, cracks, and especially check around the clamps. This is important for determining coolant loss. Also, hoses have nylon lining inside of them...the nylon can burn inside the hose from the heat of the coolant, while the hose rubber is just fine. When squeezing hoses, listen for the nylon and make sure it isn't cracking...it is usually audible. If you hear it cracking, you may want to replace the hose just in case, though I don't really know if that is a sign of a failing hose. Once you have had a run in with unusually high temperatures, it may be a good idea to replace the hoses once the problem is solved, just to insure they are strong. Also look for leaks down at the splash guard, under the car, and at the indicator above the clutch fan pulley under the water pump. Often water is lost in boil-over through the overflow container right when the car is turned off after a long drive. This is caused by "heat soak". Once the car is turned off the cooling system isn't cooling off the engine so it heats up significantly quick for a couple minutes. As long as the boil over isn't excessive this is considered normal. Keep a watchful eye and monitor these things. Coolant can also come out of cracked hoses during heat soak. Of course any loss through hoses indicates the need to replace the hose..
3) It's good to do a pressure test when you notice any coolant loss. Get it done right away. This is done with an adapter you place where the radiator cap is put on. It is a pump that increases pressure in your cooling system to check for holes in hoses, the radiator, and other components of the cooling system. It's an easy and effective way to look for leaks in your system. You should be able to get one for free from any shop. Don't let them charge you...you'll find one that won't. Of course you can choose to have him do any necessary work, but you can probably do it yourself. Check for leaks carefully when getting the pressure test done. It should be obvious if you have a leak. Replace the faulty part and then get another pressure test to ensure no other hoses, etc, have problems. Do this until there are no leaks. You may also consider a complete cooling system diagnostic from a trusted mechanic. It could save you time, effort, and money.
Note: Try to participate in any work done by a mechanic. Most likely they won't let you near the car when they work on it, because of protection laws, but mechanics love that law because it totally gives them an advantage to lie and become the only ones who know how to fix even the simplest of problems. Try to become an expert with whatever you can on your car. During the pressure test you can generally participate because it's so easy they do it outside of the garage.
4) Try to find out if it's really overheating. You don't want to waste efforts trying to figure out what's wrong when there's nothing wrong. Some mechanics have this digital heat gun they can just point at a hose or metal part of the cooling system (like the metal pipe by that has the radiator cap on it...if you can call it the radiator cap) and instantly have the temperature. My car was reading about 240 when it was really at about 220. You can replace a bad temp. sensor cheap and somewhat easy. The process is explained on Morgan's site. (By the way, 220 is still too hot to be running. If you don't trust the gun thinger, then get a $20 temp gauge that can hook up to the block somehow and check the heat that way. I for one trust the technology and the simplicity of the guns. Mechanics have mixed feeling, but most believe the guns to be accurate within 5-10 degrees which is sufficiently accurate.)
*Very important note: If your gauge is reading unusually low temperatures, it may be a sign of low coolant level. If there is no water in your engine, the gauge could read zero (0), even thought in reality it could be past the 270 scale if being run without coolant. Make sure there is coolant in the car!!!
5) Clear any obstruction of airflow into the radiator by removing bra's, little rocks, etc, from the A/C condenser and radiator. Also look for fuzz and dirt stuck in between the two units. This is time consuming and most likely not part of the problem, but major airflow obstruction is common on the Z with the way the radiator is set up. Since you do so much to ensure that the radiator isn't covered with junk, such as removing the front bumper cover, fan clutch etc...you may consider looking ahead to other things you might have to do to the radiator, such as rodding out, re-core, or even replacement. It wouldn't be fun in my opinion to take the front bumper cover off 1or 2 times just to decide later to take it off a third time to replace a major part. Clean debris and other obstructions from the condenser and radiator. This could involve removing the front bumper cover. Many times you cannot see radiator obstruction on the Z because it hides itself very well. Of course if you plan on taking off the bumper cover (fascia) you may want to check other items, like hoses, since they are easier to work with after everything is already out of your car. You may want to take the radiator out for a back flush, to rod it out, or recore it. These aren't preventive measures so much as they are fixes.
6) Timing is easy to take care of and since it's part of regular healthy maintenance you may want to do it anyway. If you know how to do it yourself then great, otherwise pay $45 for a good tune-up and make sure they look at the timing. Don't let anyone get away with replacing the plugs and nothing else during the tune-up.
7) Do not overlook this one!!! Though usually only thought of after the flush, rad replacement, thermostat and water pump, these Z's are cooled with a viscous fan clutch. This sucker wears down from spinning at close to the speed of the engine. As the engine runs faster and hotter a silicone liquid inside the fan clutch expands and the fan spins closer to the rate of the engine...the fan is temperature sensitive. This fan may seem intimidating to replace...but it's actually the easiest thing I 've ever done on my Z...and was in fact the first big step to solving my overheating problem. The part costs $40 or so and the labor is four bolts, a cleaning of the fan if you are a detailer, and about 30 minutes. My car has never had a problem in the city since...I still had problems doing 75 on the freeway, but still it ran up to 40 degrees cooler in all situations. The fan doesn't effect the car as much at higher speeds, but without a properly operating fan, you would heat up very quickly. One quick way to check to see if the fan clutch is bad is to give it a spin (with the car off). It should resist movement and stop immediately after you let go. If it continues to spin at all, it needs to be replaced. They supposedly lose 100 r.p.m per year. Also, at the back of the fan, if you see a thick liquid catching a lot of dirt, it could be silicone leaking from the fan clutch...a definite sign of failed hardware.
Up to now, the most you could've spent is about $80 or so (considering you do your own work), and it could've solved your overheating nightmares. You can also replace the fan clutch with an ELECTRIC FAN, probably a good alterative. It will increase hp a lot (if your fan clutch is relatively new) or slightly (if your fan clutch is worn down), since the electric fan is not belt driven. Consider that electric fans fail, and when they do, they fail entirely. The fan clutch loses it's effect over many years but even if it's old it's still doing something. You may also have to get a new alternator that has higher amp output ('89-90 Maxima alt. should be a direct bolt on...though it has serpentine pulley...you may either have to replace the alt. pulley or get a turbo [serpentine] crankshaft and water pump pulley) to compensate for the draw of the fan (15-20 amps....30 amp fuse).
8) You can always try flushing the cooling system out. This usually helps the radiator. There are good and bad things about a flush. If your system is only lightly obstructed, a flush will do pretty good, but then again light obstruction usually doesn't cause overheating. If there are some big chunks, you have to consider that if they enter the radiator where there are small passages, they can clog it up worse than before. Back flushing the radiator is a much safer method but takes a lot of effort on the Z. You have to remove the radiator by removing the fan clutch, splash guards, intake assembly, the front bumper cover, and much more. You can learn this detailed process on web sights and in you trusty Z repair book. It's intimidating, but easy once you've done it the first time. Dealers and mechanics charge about $300+ just to remove it. I've had some mechanics tell me that they don't work on Z radiators because they end up losing money repairing their own mistakes while trying to fix your problem. A flush can solve your problems so don't cancel it out because of the dangers I've mentioned.
9) What about the thermostat? It's supposed to open up fully when your car hit's 180 or so. The problem is that a t-stat can get stuck open or stuck shut...usually not in between. If it's stuck shut you can only drive a couple blocks...maybe a few more in really cold weather, before your car completely overheats...if it's stuck open, then you should never overheat unless you have some of the other problems. Some people take the t-stat out completely to avoid the possibility of the stuck-closed position...which of course is the dangerous one. The stuck open case only makes it hard for your Z to get to normal operating temperature fast enough for you to beat people off the line on the way to work. The most common $70-$130 mistake (if done at a shop) is replacing the t-stat because out of instinct you think that it is the cause of overheating. It's very seldom the t-stat. It's so popular to do it 'cause in other cars it's so dang easy...and only costs $10 for the part. Labor for the Z is what makes everything cost more.
Note: Thermostats can be placed in backwards...be careful not to do this...it will never open. The t-stat is a part than can be easily replaced with the wrong t-stat.
10) If you're still having overheating problems, then you can start doing what everybody does...that is the major radiator work. My opinion on this one is quite simple. If you plan on recoring or rodding out the radiator...save yourself some time and replace the dang thing. The thing is, it's going to take a bunch of hours to get the radiator out of the car just to give it a good back flush. If you're like me, you have a Z over 14 years old that probably wonder's why it's still got the stock radiator with years of heat insulating tar, pebbles, and paint over spray on it. Instead of taking the radiator out five times before you decide it needs to be replaced, just replace the thing and take it off the list of problems. However, sometimes rodding it out will solve the problem just fine and save you a couple bucks, so decide yourself what kind of time and money you have for the radiator. The radiator is what ultimately fixed my overheating problems. I bought a Modine radiator (one of the best brands you can get). The core is twice as thick as the OEM. Others have bought double-cored radiators which would also do the trick. You should consider what would be best for you. My Modine can cool the car down 40 degrees in a matter of seconds on quick acceleration (such as entering the freeway)...its pretty cool...of course once I get to a steady speed the car warms back up. If you want to get the Modine, I bought mine from Haun's Radiator and Automotive...only cost $140...that's almost $100 bucks cheaper than all the other places I looked. Others found the same radiator for $170 or so closer by there own homes. The number for Haun's is (801) 785-7623. Please let me know if you buy from them.
For some other great radiator info, go to RADIATORINFO.com
Shaun from the ZBoard followed up with me on Haun's service. On April 06, 2000, they were still selling the Modine for $139 with $14 shipping (in Shawn's case) and for $14 they two-day aired the sucker!!! Sounds like great service. I guess you should also be aware that Haun's warehouse for the radiators is only open in the morning, so call them in the morning and not the afternoon. They will ship it the same day if they have it in stock.
I have told about 100 people and no one has told me if they called or bought from Haun's. I just want to know how the service is and what shipping costs you...if they are rude, I don't want to refer them anymore...but if they're good with you (like they were with me) then I'd like to continue refering them. I couldn't find the MODINE any other place for cheaper than $200, though other were able to find about $160.
Note: After rodding out a radiator, the core may not be strong enough to withhold it's part of the job and could blow on you. Not common, but possible.
Note: Just because your car overheats when the A/C or heater is on doesn't mean that you need to replace the heater core...it's not likely that you would have this problem. Other signs of heater core problems are coolant dripping inside the car and hoses inside the car that split under pressure due to overheating while using your environmentally manipulating components. If hoses loose water inside the car it's a mess and by the way, it's very very hot, perhaps even steam before it hits the carpet, so tell the passenger to lift their feet.
If you've done everything stated above and you still have problems with overheating you may consider moving from Death Valley, California or Phoenix, Arizona and while your at it stop trying to do 80 uphill in fourth. Heavy traffic driving can normally cause a slight rise in engine temperature but nothing a good cooling system can't handle. The following are things that, after all has been done, you may have to admit.
The order of these fixes seems to be pretty accurate for anyone's overheating problems, but if you are sure that the problem is the radiator because you hit some animal and now it leaks or it blew, of course take care of it first thing...the same goes with any other obviously bad parts. As a last note lots of people are worried about springs inside the lower and upper radiator hoses that kept them from collapsing at high temps. These springs were used in "the old days" because the hoses were soft even when new. Nowadays, the hoses are strong enough on their own to support the pressure and they won't collapse. Be aware, however, that if you have never replaced your hoses the springs should probably be in the hoses. The springs can corrode overtime so if you have original hoses and no springs, they have probably completely corroded. Also, if you have overheated and have newer hoses, the new hoses could be damaged and susceptable to collapse. If you have new hoses and have never overheated, then drive with a free conscience.
Email me using the contact link above if you have comments, suggestions, or questions.
By the way, my '84 Z doesn't overheat anymore and now I can worry about making it pretty...they go faster when they're waxed.