Hi All, I've been driving and maintaining zeds since 1995 and am fortunate that I am able to do most repairs myself with help from a few good friends. Along the way I've resolved most problems but the most persistent are those associated with heating and cooling and this is now very topical with the current heat wave. Anyway, here are some of my thoughts about cooling: a) I have several zeds and two of them have after-market temperature gauges. I also have Conzult and Datascan and have sometimes monitored temperatures on my laptop with the after-market gauge. To generalize, the driving temperature with the A/C "ON" I simply add 60 degrees Celsius to the ambient. That is, with an ambient of 30 Celsius the driving temp with the A/C "ON" is about 90 Celsius. Please note that the stock thermostat opens at 76.5 Celsius and when idling from a cold start the temperature should stabilize at about 80 Celcius. So, with the A/C "ON" and from a cold start the idle temp is say 80 degrees Celsius but, this is not applicable to a hot idle due to heat soak. Obviously, if the car has been driven the idle temperature will be above 80 Celsius and often reaches 95 Celcius or hotter on days like present. That is, on a hot day you drive at 85 Celsius then stop the car. After say 15 to 20 minutes heat soak will cause coolant temperature to rise to above 95 Celsius. To drop the coolant temperature you need to pump the coolant around and it will take quite a while for the temperature to fall back to 85 Celsius on a hot day. Incidentally, when the A/C is "OFF" the temperature while driving will fall by about 4 degrees Celsius. Remember, after the coolant temperature has risen above 95 degrees Celsius due to driving on a very hot day or due to heat soak then it takes a long time to fall (if the ambient is low enough to allow for such a fall). b) The usual suspects for prolonged high coolant temperatures are as follows: 1) Thermostat not fully opening. This is quite common. I have tested many new and used thermostats using hot water with a bulb thermometer. I strongly recommend that you always test a new thermostat before installing as I have found new thermostats also to be faulty (do not fully open). Testing is easy with a saucepan of boiled water and a bulb thermometer. A thermostat is fully open when the moving centre plate travels to the end of the side-shield (full open distance is about 12mm). When changing the thermostat also inspect the nearby short steel manifolds and replace if they are rusty (a very common problem). Rusty short manifolds are a common source of coolant leaks - and you can't easily see this when it does leak! Remember, the short rubber hoses are held in place around these steel manifolds using spring clips - so replace manifolds if rusty. 2) Viscous clutch not locking. There is an easy test for this but you need a friend. Take car for a short drive until it reaches operating temperature and then stop, turn engine "OFF" and open the bonnet. Using a flexible plastic ruler at least 300mm long, place one-end of the ruler firmly against the fan blade with your hand safely at the other end. Have your friend then start the engine. If the ruler holds the fan stationary then the viscous clutch is stuffed. If the fan forces the ruler aside then the viscous clutch is probably ok. Incidentally, I have had no problem thus far using a Davis-Craig viscous fan (am I lucky?). Also, if your fan blades are cracked (usually at the mount near the bolts) please replace fan as soon as possible. 3) Shrouding and Radiator Clogging Please ensure that all shrouding is fitted properly. This shrouding is designed to guide air around the engine for efficient cooling. Shrouding includes the lower radiator shroud and particularly the rear stone guard. Don't whinge about poor cooling if you don't have these guards in place. To reach the radiator air has to pass the oil cooler and A/C condenser. Please take a few minutes to flush the fins of years of accumulated crap caked to the outside of these cooling devices. You will be surprised at the number of bugs, paper, soil , feathers and grime that is removed with a power spray. Give your 20 year old radiator a birthday and have it rodded (In the ACT I use Renner Radiators located at Fyshwick - $140). Rodding is done by removing one of the plastic end tanks and then pushing a metel rod through the coolant lines. Check the radiator has been rodded by looking for press marks at the metal retainers for the end tank that was removed - a power flush is a second best solution. If you have installed a FMIC then get a thicker radiator so as to hold more coolant - if you still have problems then you made need to install air guides to direct air onto the radiator or have "speed holes" cut into the bonnet as an alternative way to get cool air into the engine bay. 4) Radiator Cap Perhaps the most common cooling system failure is a faulty cap. A TT requires at least 1.2 bar cap (NA is 0.9 bar). Do not get these confused. New caps can quickly become faulty when installed incorrectly (they are made using thin pressed metal). Check that the two metal folds at he base of the cap are at 90 degrees and are not bent at 45 degrees due to wear. If bent then carefully use pliers to adjust. 5) Coolant level Check coolant level at least once a week. This includes the overflow bottle. If your overflow bottle is faulty then replace it asap as it is an important device to ensure proper cooling. On occasion blow into the black rubber hose to the overflow bottle to check for blockages (errr....don't swallow the coolant). Incidentally, I use a coolant concentration mix of approximately 1 part concentrated coolant to 2 parts water. A stock cooling system hold about 7 to 8 litres (so a total of 2.5 litres of concentrated coolant is sufficient). c) There are some other less obvious causes of overheating such as: . Blockages in the block - particularly by silicone. I have seen coolant galleries (usually in a head gasket) completely blocked by idiots using far too much silicone when reassembling say during a 100k service. After assembly, if the silicone is still soft the excess amount will be pushed around until it is forced into a tight place - particularly the head gasket! Also, when a water pump fails have you wondered where the impeller blades have gone - yes - into the block (I have found 5 blades in a block). Yep, welsh plugs can also disappear in blocks when idiots push them into the block while trying to remove and then can't be bothered fishing them out again. However, most coolant galleries are restricted or blocked with severe rust due to not using a rust inhibitor with the coolant (fortunately I think most coolants have rust inhibitors). . Blown head gasket Yep, shit sometimes happens and the head gasket is damaged. If this happens exhaust gases can enter the cooling system and rapidly heat the coolant. If this is prolonged then the cooling system gets pressurized and the weakest link is usually the heater core. Alternatively, oil enters the cooling system and you end up with a cappuccino in the cooling system. Well, that's all I can think off for the moment. I'm sure other owners will comment or add more (and sorry for any spello's ). Cheers
Thank you for the writeup, I found it to be very informative! I don't currently have cooling issues with either of my zeds, but will definitely save this writeup for future reference. -Kirill
Great write up Zcar91, Mods this should be used in the tec section as a sticky somewhere. Well done , covered all bases too. Cheers Patrick
Good write up John All mandatory stuff for a well maintained cooling system, and nice to see your still around here. Additional stuff i have done is to have a slotted nose panel to allow more air to get to the radiator. Fitted a top radiator guide, stopping the incomming air from going up and over the radiator. also made a aluminium bottom panel with a slotted scoop to force air from underneath up through the radiator. Also i have wired my air con condensor fan to a switch in the cabin that i can turn on and off at will. Lastly i also run a vented bonnet to get as much of the heat out of the engine bay as possible. all with the aim of having the Zed run as cool as possible. .
Hi Ron...>> yep...still around....and on occasion drop-in on the forum. Looks like you have your cooling well covered. I forgot to mention a couple of other aside issues associated with proper timing, running-lean (boost/vacuum leaks) and using too-much right foot pressure. Perhaps another posting in a day or two. Cheers
fking awsome Staight to the pool room...erm i mean Tech section I hope the mods agree I know there is already good info there but this is an awsome overview all in 1 place.
