Strange but, true running hot!


I have a Daihatsu Sportrak 1993, and yes I know a number of you out there have had heating probs, but I have a strange one!
When I use the vehicle on the flat it is ok for a while (30/40mph max in Guernsey) on a slight hill or incline the gauge rises very quickly, but not to overheating point, on switching off the engine I can hear the water being pushed into the bottle, a pressure and head gaket test has been carried out and seems to be ok, the rad cap is a 0.9 bar but seems a little short and I suspect it is not seating correctly. Does anybody have any idea`s please.


I assume you will not have been not topping up the reservoir on a regular basis. If top up is needed then your loosing coolant. A pressure test suggests the head gasket is OK. If your loosing coolant it could be escaping from the radiator cap.
You could renew the radiator cap or you could cut a rubber seal to replace the seal found inside the rad cap. The cap lugs get stretched so the cap lets water/steam escape to the atmosphere. Alternatively squash the lugs so the old cap fits very tight : I prefer to cut a new seal from an old inner tube.

Water forced into the 'bottle' suggests the water pressure is too high due to boiling of the coolant. The thermostat could be stuck partially closed. This allows some coolant to flow but when the engine is worked the coolant cannot rapidly circulate and cool. The water towards boiling point expands into the reservoir.
Test --- when the engine is very hot touch the bottom of the radiator. Is it significantly cooler than the radiator's top edge? If so the thermostat needs checking/replacing. If the problem is due to the thermostat eventually the head gasket will leak due to the excessive water pressure.
Also note that the head gasket can leak into the oil. Check the dip stick and oil filler cap for signs of 'grey matter' or water droplets.

Similar problem

Hello, i have a similar problem with my 1990 Sportrak.With the gauge reaching the middle and then dropping to normal(that happens all the time),when i switch off the engine and although the gauge in normal a can hear the water from the thermostat boiling and when i remove the container cup wich conects with the radiator through a rubber pipe, steam is coming out of the pipe.If i don't remove the cap with the pipe, the water in the container is boiling too.Keep in mind that radiator is changed with a brand new and the thermostat changed with a brand new genuine Daihatsu part.Do you think it might be the radiator cap(it's the old one)?Any advice?
Thank you.


1. Do you frequently top up the coolant?
2. Is the radiator wet on the top edge ... usually in the area of the top hose or along the top seam? Check when the engine is hot and running.
3. Is the water pump belt a tight fit?
4. Is the water pump working? When the engine is hot open the reservoir [not he radiator cap], look at the reservoir coolant level and rev the engine. Does the coolant level rise and fall. Do any air bubbles appear in the coolant?
5. Any possibility the thermostat has been fitted up-side-down?

hello again,everything seems

hello again,everything seems normal except the boiling noise from the thermostat and water coming out of the reservoir's rubber pipe(when engine hot and a couple of min.after switching off).No need to top up the coolant,thermostat fitted corectlly.When i rev the engine the coolant level doesn't change but i think bubbles appear as steam and water comes out of the pipe.
please help!


From CD Guide .... Engine Overheats.
1.Water Pump Belt loose/broken
2.Blocked Radiator - reverse flush
3.Faulty Water Pump, Thermostat, Core Plugs
4.Ignition Timing retarded - check timing.
5.Radiator Cap faulty - renew
6.Cylinder Head is cracked, Head gasket is leaking
7.Blockage in coolant circulation - force flush whole system [hose pipe]

Did you replace the thermostat with an exact type? Some thermostats have a small open hole plus the opening valve, to allow coolant to vent for expansion of coolant.

PS ... if you have bubbles in the coolant's overflow reservoir, it is likely the cylinder head gasket is leaking. Compression forces the gas from the cylinder throught the head gasket and into the coolant. The compressed coolant escapes into the reservoir where gas bubbles emerge at the reservoir's filler neck.