Fluctuating radiator temperature

Electron1

Electron1

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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?
 
Listen for a noise when the car is on by the water pump to determine that.. or else check your thermostat
 
Also, you don't only need to do it pressure test, open your radiator cap and start the car.. of water starts pouring out than it's your head gasket.. if it doesn't, it's not
 
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?
Click to expand...

It makes a lot of sense to me, another thing is the temp gauge mechanism itself might be faulty, maybe check the wiring thereof if you can, the earth might not be good or something.
 
It is a 1989 Toyota corolla 1600 16v carburettor.
Click to expand...
If the water pump has never been changed there's a chance the impeller blades have rotted away if the correct antifreeze/water ratio has not been used.
 
Thanks for the feedback. I hope the new thermostat is not faulty, as there was no difference between the old and the new one. Replacing the pump is my gut feel, is a pressure test still worth doing?
 
You can do a pressure test.. but if you use my theory above with the radiator cap open and starting the car, you could get a quick idea.. just to save money .. you know spending on cars is a lot of pressure.. but good luck bro.. I hope it's not a big problem..
 
So just called a radiator repair shop. What I haven't said is temp stays higher than normal. Needle doesn't go up and down all the time. Town driving it is better, highway driving is when it gets hotter. according to the radiator guys, if the pump was not working efficiently it would overheat very quickly. They say it is radiator that is not efficient.
Mr Ree there is no loss of water. when starting the car there is a quick initial surge, but that is all. I had checked that first and throughout I have been checking that nothing unusual is happening with the water.
So now what should be next step?
 
nivo said:
Waterpump is shot.
The impellers are worn.
Click to expand...
How can I test that before laying out more money?
I know the cooling is not efficient, hence the higher temps, but how do I determine radiator or water pump is faulty?
Leaning towards the water pump due to the assumed difference between the sensor in the block , and the fan relay not always staying on when temps are showing as being hotter than normal - as if the flow of water is not enough to cool the block. I guess it is possible there is a blockage in the ports in the block too.
 
higher revs - higher temp
low revs - low temp.
slow speed means water is pushing through easily, at higher speeds, worn impeller will not push enough water through to cool engine.
 
Electron1 said:
How can I test that before laying out more money?
Click to expand...

Remove the thermostat and drive. What happens to the temperature?

Then consider doing a reverse flush of the engine by disconnecting the radiator.
Remove radiator and reverse flush as well.

There's either a restriction or the pump is kaput.
 
nivo said:
higher revs - higher temp
low revs - low temp.
slow speed means water is pushing through easily, at higher speeds, worn impeller will not push enough water through to cool engine.
Click to expand...
Nivo that is the type of explanation I am looking for. OK so a replacement pump it is. I know from draining it a few times over the last week that water seems to flow easily through the radiator, so this is why I am not convinced on radiator. I hope a new pump will sort it out.
 
thechamp said:
That's done already unless by sheer bad luck the new thermostat is faulty.
Click to expand...

Easy to test.

Take it out and drop it in boiling water. If it opens it's working and if you remove it see if it closes. Also make sure you don't have water in your oil. If you take out the dip stick and the oil is a caramel colour - Head gasket blown.

If all else fails, in the older cars you can remove the thermostat permanently. Just remove it and see what happens. If the car temp stays level then it's fine. Thermostat is to regulate the temps so the engine temp is at peak operating temperature. If you remove it your engine just runs cooler in general.

Only saw now, you say the higher the revs the higher the temp?
Could be a timing issue. Engine is misfiring causing the surge in temps. I have a feeling your timing is out by a fraction ;)
 
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Could be timing, but this was a fairly sudden change in the last week and a half and have been trying to sort it out. Normally temp is absolutely stable. No recent adjustments to anything on the car and engine running well. Anyway the pump is ordered and I will fit it this weekend. Also I had fitted a new thermostat and it made no difference.
 
Electron1 said:
Could be timing, but this was a fairly sudden change in the last week and a half and have been trying to sort it out. Normally temp is absolutely stable. No recent adjustments to anything on the car and engine running well. Anyway the pump is ordered and I will fit it this weekend. Also I had fitted a new thermostat and it made no difference.
Click to expand...

Timing is crucial to get right as you state. In the good olde days when cars had carburators and points and distributors and timing was set and fixed it would have been easy to eliminate a timing issue. Now that somewhere in the vehicle, there is a computer chip, deciding for you what the timing should be dependent on sensors all over the place it would have to be diagnosed by an "expert" with one them thingies he plugs into your car .

Stuck in an advanced state after a spell of high speed driving then suddenly dropping and the staying low even when again accelerating would indicate that a thorough check of the automatic advance thingy and its control circuits and sensors would be in order.

Yes it could be a water pump, and I hope it is but do not write off an issue with timing either.
 
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Geoff.D said:
Timing is crucial to get right as you state. In the good olde days when cars had carburators and points and distributors and timing was set and fixed it would have been easy to eliminate a timing issue. Now that somewhere in the vehicle, there is a computer chip, deciding for you what the timing should be dependent on sensors all over the place it would have to be diagnosed by an "expert" with one them thingies he plugs into your car .

Stuck in an advanced state after a spell of high speed driving the suddenly dropping and the staying low even when again accelerating would indicate that a thorough check of the automatic advance thingy and its control circuits and sensors would be in order.

Yes it could be a water pump, and I hope it is but do not write off an issue with timing either.
Click to expand...

Even a worn spark plug can cause timing issues. Sometimes the timing is out by such a fraction you won't notice it. That is why your fuel usage increases when your spark plugs are worn. But for it to make a noticeable difference on the heat gauge it would have been a sudden change in the timing. Belt could have slipped a tooth, maybe electronic failure somewhere in the ECU.

But yes, I would suggest fiddling with the easy stuff first to see if it sorts the issue. Have you noticed an increase in fuel usage? For it to get so hot that you see a difference would also bring about higher fuel usage if it's a timing issue.
 
I would leave the thermostat out. It does sound like the water isn't circulating properly. If the water circulates like it should driving on the highway would cause enough air to pass through the radiator to keep the car cool. This for me can only mean its the water pump. Take that off you should see visible wear on the propellor fins and hear and feel if the bearing is faulty.

Or it can be a blockage somewhere in the system, press on all the pipes to feel that they are under pressure when the engine is running.
 
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