Fluctuating radiator temperature

I got the water pump, but chickened out today as I have to take off timing belt cover and an engine mount to get to the water pump. Will arrange with a mechanic to do the job for me.
 
Electron1 said:
My Radiator temperature fluctuates and I have been trying to resolve it as the vehicle is running hotter than normal.
It is a 1989 Toyota corolla 1600 16v carburettor.
Replaced Radiator Fan - previous fan faulty and caused fan relay to burn out (strange the fuse didn't go)
Replace fan relay as above.
Temperature still fluctuated badly (fan not kicking in when needed), bypassed relay so fan on all the time, still fluctuates.
Replaced the thermostat and the fan temperature switch (removed bypass on relay).
Fan seems to run more regularly however still fluctuating temps.
Drained antifreeze (probably too strong not correct solution as recommended) and used Wynns radiator flush driving about 40 km on highway at 120km with solution, still ran hotter than normal, used heater fan to keep temps down.
Drained solution a few times to try get as much of it out as possible.
Now running on mostly water, but temps still fluctuating.

No leaks, no bubbles, or oil in radiator water. Oil is normal colour, so no water in oil either.
Radiator drains quickly so I don't think it is blocked.

The engine temperature sensor sits in the block, above the fan switch which sits just after the thermostat.
My theory is it could be the water pump as perhaps there is not enough pressure to circulate the water and the water in the block is hotter than the other side of the thermostat. Does this make sense?

I have heard a number of opinions, one being I should get a pressure test as it could be the head gasket, but then I should see bubbles or oil in water, or water in oil. Also will a pressure test prove the efficiency of a radiator? This is the temp stays higher than normal even with fan relay bypassed and heater fan on full when the engine is running at higher revs. Temp is actually closer to normal when driving at lower revs in town that when driving on highway at 120.

Advice anyone?
Click to expand...
What was the problem? I have the shame problem at the momwnt
 
namzsteve said:
I'm sure OP got it sorted by replacing the water pump, yours may be a different part failing. Start with the small things.
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I did flush the radiator and put in antifreeze, when my car is standing still the fan goes on normal but when im driving on a long road or free way my heat gauge rises
 
When last did you change engine oil? 3/4 of the heat from your engine is dissipated and transferred by the oil. Not saying it could be this but if you have less/old oil then it can be the culprit.
 
I still have a carburated jap 1600 1998 pickup going well. Over the years I replaced the radiator 4 times, each time I replaced the thermostat and drilled a 3mm hole in the seat of it just because I was working in the coolant area.Its till going stong and steady temps, waterpump never replaced. I does keep proper antifreeze coolant 50% mix in readiator.
Each time the radiator was replaced I was led to it being the culprit. Engine oil was always replaced no more than 5 000Km, so at 300 000Km,s+ the engine is still clean inside. With cooling issues you have to be a quick observer.
 
Alexster said:
I did flush the radiator and put in antifreeze, when my car is standing still the fan goes on normal but when im driving on a long road or free way my heat gauge rises
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Have you removed the thermostat (temporarily) and tested it?
 
Alexster said:
What was the problem? I have the shame problem at the momwnt
Click to expand...
Apologies only saw this now.
I did replace the water pump. It still seemed to overheat occasionally. I eventually bypassed the fan relay and let the fan run all the time for a few weeks. Replaced with a better relay from Motolek. The fan eventually failed in about October last year and had to replace it again. So far all is good. The suggestion about replacing oil more regularly makes a lot of sense. May well have been old oil. I replace oil at 10 000km intervals.
 
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