Strange overheating problem 4E-FE

[Akane]

I'm having this crazy strange overheating problem. The symptoms are:

1) Car warms up really fast from cold start, like within 1-2mins of driving the needle will reach half. This progressed gradually from normal working order a few weeks ago till total overheating.

2) heater start to lose it's ability to provide heat, this progressed gradually as well - a quick blip on the throttle will bring heat back for a moment. Idling at the lights will make the heater cold, once get moving it'll be warm. now it's just total fail, cool breeze reguardless of engine and road speeds

3) car will overheat when stopped at the lights, this has been progressing gradually as well, from a quick blip on the throttle will fix it till now which revving does not help, even driving normally will cause the temp needle to reach 3/4 way up, and if continue it'll overheat.

4) cooling system loses a tiny bit of water and usually will need to top up every 2 weeks, but very little - about 100ml


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Waterpump, cambelt is new since 5,000kms ago
Waterpump is some random brand
Did not use any anti-freeze since 10,000kms ago
There is signs of rust.
thermostat is new since 40,000kms ago

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Did remove thermostat - no difference
rubber piping leading into and exit out from the heater core is cold, tested while tempreature needle is 3/4 into "hot" and heater on full hot.
Radiator is warm 1/5th way down from the top only, from then onwards is cold, tested during needle has reached 3/4 way into "hot".
Water pipe leading into radiator is quite warm
water exit out from the radiator is cold
Stuck garden hose into radiator - water is exiting freely at drain point.
Stuck garden hose into both heater core inlet and outlet, water flowing freely - did also the same on engine side - water flowing freely.
Blipped throttle with radiator cap off, there is signs of water movement although not severe.


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Turned water pump by hand - smooth operation.

I suspect the waterpump has gone bad, but it's not leaking or making any whining noises, and 5,000kms since new, and i've read to have the waterpump blades all worn out it'll take YEARS of neglect?

If the radiator is 90% clogged, I'm sure the water outlet pipe will be hot?

It seemed like the car needs to be revved to keep cool, but now revving doesn't help anymore. A few days ago I have to drive in 2nd gear (automatic) to keep the car cool, putting it into drive the heat will start to creep up. But now it's not making a difference it's overheating reguradless.

Any ideas anyone?

[Malcolm]

definitely sounds like a blockage, or several blockages - might have had a lot of corrosion or other gunk in there in the past? I've found on both 3sgte's that I've pulled apart that the radiator bypass fitting on the back of the block was entirely gunked up solid, presumably because it's somewhat of a low point and i guess sediment settles there when the engine sits for a while - there could be a similar thing happening somewhere in your cooling system?

My suggestion would be to get some stiff wire - ie welding rods or thick piano wire, and try threading it through each pipe in your system(especially hard lines).

It also sounds like the radiator is pretty blocked if the temperature distribution is that bad - if you can get your hands on an IR thermometer then get some actual numbers, blocked rows will be considerably lower temperature.

You could test how well the water pump is working by removing the outlet pipe and pointing it up in the air, then starting the engine very briefly. See how high the fountain goes, I have no idea how high it should be so do the same on another car to see whether it's comparable

[Malcolm]

Hang on, I was assuming a horizontal-flow radiator but now I realise that's probably not the case. If it's only hot part way down, that indicates there's bugger all water flow through it - so either blockage restricting flow or water pump being useless.

I also realised the hose on the water pump will be the inlet, and the outlet probably pumps straight in to the block. If this is the case then pull the upper hose going from head to radiator off (remove at radiator end) and squirt in the air

[sergei]

sounds like a lot of gunk in the system.
Especially radiator.

[sergei]

I've seen this exact problem with 4EFE starlet.
Exactly same symptoms as your one.
Turned out blocked radiator.

[Akane]

I thought about blocked radiator as well, but when i shoved a garden hose in the radiator (top), the water drains freely from the bottom? No signs of bloackages...


ACTUALLY

Duh. I'm dumb.

Garden hose could be feeding the water to the radiator, but the water is going from the top tank, straight to the engine, then out the bottom hose into the bottom end tank, then out the radiator, bypassing the whole core

Ok lemme check that out tomorrow first. Stay tuned.

Edit: but that doesn't explain the cool heater at all. and the heater is definitely not blocked coz I shoved the garden hose into the inlet and although there was rust coming out from the outlet for a moment, then it turns clear, and it was very free flowing.

[Akane]

I also realised the hose on the water pump will be the inlet, and the outlet probably pumps straight in to the block. If this is the case then pull the upper hose going from head to radiator off (remove at radiator end) and squirt in the air

The water inlet and outlet is actually both at the end of the engine, although I think it gets routed somehow just under the manifold. I've pulled a lot of hoses off and made sure they're all free flowing by putting garden hoses in everything, and they all seem to be

[soven]

What did you change before this started happening?

Did you bleed coolant properly with heater on full etc

[mjrstar]

is the engine actually getting hot? sounds like an indication issue...

[Akane]

I changed the waterpump (which was leaking, it was dead) and cambelt.
No to full engine burping.

I think it is getting pretty hot, steam is escaping and stuff, and the heater is COLD, like NO WARMTH at all, even with driving around a bit.