Overheating problems still

[one eared steve]

Just thought i would ask this one again as i am still having trouble.
I have a 1994 440 se 1.8 b18u that keeps overheating.
I have replaced the thermostat and the water pump and the air filter and the water pump drive belt and flushed the radiator twice and topped up with the correct coolant.
The temp gauge works fine as does the cooling fan on the radiator cutting in and out as it should.
When driving it warms up slowly like normal but still gets hot to the point when the fan cuts in (it was minus 6 outside at the time) and out with the gauge about three quaters of the way up.
The car uses no oil or water and has good compression on all 4 pots.
Any ideas? As this is annoying me and can't seem to find the answer.
Am i missing something silly or have i just got to put up with it.

Cheers steve

[Clan]

is the engine actualy overheating ? Ie boiling up? It could well be a gauge problem there is a small circuit board that controls the gauges and this can play up ..

Assuming the gauge is ok , the only other option is the radiatior blocked or all the fine fins rotted away ... when you think it is hot and the fan is running the air being blown back from the fan should be quite hot , if its cold it will be a blocked radiator .

[one eared steve]

The radiator isnt blocked as both top and bottom hoses get hot as does the water in the expansion tank. It is definatly overheating as i have checked the water several times just to see if the gauge is telling me the truth. All the fins on the radiator seem fine and i have brushed all the dead flies and things out to make sure it is clear and allowing the air to it ok. I also presume the sensors are ok as the car starts first time every time hot or cold wet or dry.
This one has got me stumped and may well have to put up with it for now unless anyone has some ideas?.
cheers steve

[Clan]

I say blocked , meaning the inside of the radiator furred up but will still allow the passage of coolant yet not transfer any heat to the fins ..
When the engine is over hot you shouldnt be able to hold the top hose , if you cant hold the bottom hose either without burning yourself , suspect the radiator ...

[one eared steve]

Out of interest wereare the cheapest radiators these days.
would prefer a new one but no doubt stealerships are out of the question.

[Clan]

Try them , radiators for the larger volvos were cheaper than the factors recently ...

[veegard]

I have another problem with the cooling of my 94 460 2.0 GLE (B20F).
Temp gauge works first time after an ECU reset. Then after about 5 times it gradually degrades, until it gives me a zero-value.
Doesn't seem like the radiator fan is kicking in.
Radiator gets hot. I know this, beacuse i have an external temp sensor which is located at the tray under the radiator which i normally use to see if it's chanse of icy roads. After I've driven about 20-30km it gives me 23c, while actual external temp is about 5c.

ECU has recently been replaced, it acted the same way with the old ECU.
Resistance to the temperature sensor is wrong according to Haynes manual, but so is a lot of other things.. can't really trust it.

Where is the temp sensor that i see on the dash located? Should the fan make a huge difference in cooling the radiator? The thermostat is completely separate from this sensor, could there maybe be a combination of those two being broken? Seems unlikely.. confused!

[B20F]

The temp gauge doesn't run via the ecu. It runs directly through the wire from the sensor to the gauge. The sensor is located at the back of the head opposite sparkplug #4, the one at the right. Clean the connector, It has one wire on it. Most of the times the gauge is the cullprit though, the're notorious innacurate. The gauge reads the engine temp, NOT the radiator temp.
The fan has it's own sensor, this one is located in the right side of the radiator when you're standing in front of the car. The fan should kick in when the water in the radiator reaches 100c.

[veegard]

Forgot to check back here.. but found out most of that on my own.
Okay, my radiator temp switch clicks open between pin 1(+) and 2(e) when it reaches about boiling temperature. But 3(+) and 2(e) never opens.
The rad fan temp switch is a two stage one, and short circuiting the wire to the fan gives me a medium speed between pin 1 and 2, and a high speed between 2 and 3.
So, it should work kinda.. but I tried to expose it to boliling water, and let it sit in the bottom of a pan a bit, so it got well hot. No reaction between those two still, so I think I'm getting a new one today.

Swapped thermostat. Took out engine temp sensor, but it only has 1 pin so no way of testing this?

The gauge works like this...
First time after resetting the ECU (that also means not driving it for a long while, normally), it works. It always goes until about half temp. Then it shows about 1/3 temp next run. Then 1/5 temp.. then nothing.
But sometimes, it just works all by itself.. then it doesn't again.. completely irratic. I can't trust it atleast.

I'm an electronics guy, not a mechanic guy.. So don't know, but is it possible water pump is not working?

[B20F]

You can check resistance between the casing of the sensor and the connector. When temp rises the resistance should become lower. Sometimes a former owner used teflon tape on the threads of the sensor in stead of an original gasket, this influences the resistance. Had that happened on mine 480, replaced the teflontape with an original gasket and everything went back to normal. But on the analogue temp. gauges most of the times the print on the backside of the gauge itself is the cullprit of irratic readings.

[veegard]

I read a nice how-to in one of the threads here on the forum, so I guess I'll have to try to check that out.
But.. A 460 isn't as fun as a 480, so I'm not as tempted to tinker with it for all eternity.
Maybe I'll abandon Volvo soon, and get a Mercedes instead :o