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Well, yesterday for first time in the life of my 4g15 the engine failed, i was in the road, driving at around 80-90mph and i noticed the temperature was really hot, i instantly stopped the engine and parked and when i opened the engine bay the radiator was throwing out all the water trough the exit of the recipient on the side, of course, the water was boiling so it is expected... but one thing i noticed was that the radiator fan was not turning on.

I left the engine off till it was cooler and then filled the radiator with coolant water again, to make sure that this wasnt the issue and take the road again, just to discover that the same thing happened once again, so i decided to connect the radiator fan directly to the battery forcing it to start, to at least let me get home.

I did so, and went back home at 60mph, no more than that to not force the engine, and it didnt overheat, when i arrived at home i connected the radiator fan to the original location, checked the water and the oil to make sure they where ok and started the engine on, and left it warm up in idle speed, and, with the car stopped, give it a little gas and the radiator fan started up, so, by this im sure that its not seems to be an issue of the fan itself nor the temp. bulb...

Anyway, i went for a ride again, and the car still overheat when i force it a little bit, lets say 90mph, and when it does and i immediately park the car i notice that the fan is not ON as expected it to be since the engine is that hot, so, what is going on here?

It is a 12valve 1.5L petrol 4g15 engine, carbby

Suggestions? Tips? what can i check?

PS: Sorry for my basic English, i hope it is understood...

do a compression check..u might have a blown head gasket causing the overheating when pushing it at that speed..



Steve

good idea, i will do that, where can i find the reference values for my engine? i have the workshop manual but dont find it anywhere...

basicaly what u look for is 1 or 2 cyl's that are lower than the other ones.....say cyl 1 and 4 are a comp of 130..and 2 and 3 are 70...then the gasket between 2 and 3 is blown out.... or say 1, 3 and 4 are 140...and 2 is 90..then its probably blown out the front or rear......(or worst case a bent valve. but probably not if its been running good)



also if u fill it up with water and drive it normally so it doesnt over heat...does it lose water? (thats a good sign of bad head gasket)



I just threw out some numbers..there not actual..just as a demostration.. real numbers vary car to car and engine...my old talon had a best comp of 125 across all 4 cyl.... my new motor has 140-150..ive seen some 4g63 motors with 185-190 comp when freshly rebuilt.

hope this helps and good luck with it..if it is the head gasket... i advise to replace the water pump and timing belt at same time sine it will all be taken apart..save u time and money in the future


Steve

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Well, i found out the problem, first of all, related to compression test, the tester i had is small and does not rich the hole of spark 2 and 3, but i was able to measure the first and last ones and they where both the same, about 140, and the motor does not fail at all, and the VACUUM gauge does read correctly so i assume that there isn't any compression issue.

And regarding to water, no, in normal heat the motor does not loose any water, the reason i had to refill it with water was since the water was boling it was trowing it, but not in normal heat..

Anyway, i found out that the thermostat was broken, "it had a broken arm that caused the spring to fall off", basically i removed it in 3 pieces instead of one hehehe i removed it, made a new gasket and leave it without the thermostat and the engine does not overheat anymore (seems to, i just did a small ride of 15 miles at ~90mph and it went fine).

So tomorrow im going to the dealer to buy a new one, anyway, my dad here which is helping me out told me that there is no need to hurry, and i can run without the thermostat, it will only make the engine get warm a little slower, but not big trouble, is that correct?

thats good news ..glad to hear it was something that simple......and yes u can run without a t-stat...just in the winter the water wont heat up to warm u...but for now its ok.




Steve

I have double checked the results from my comp test and i got a value around 10 kg/cm3 , and according the manual it should be 14 kg/cm3 (199psi) and the LIMIT is 10 kg/cm3 (142psi) ... so i got about the limit...

should i be worried about this? im thinking in get the car to a workshop where i can proper measure the compression, as my tester is old and didnt even reach the hole of the cyl 2 and 3 ....

what your guys can say about this?

Don't be worried about it

just as simply as that? how come?

If it was your thermostat that was broken, it wasn't allowing coolant to fully flow through and cool it off like it should. If you replaced the thermostat and it doesn't overheat and it runs good without blowing white smoke, you should be back to normal.

Yeah, you are right mechacode, but besides that thermostat and overheat problem, which caused me to check the compression i now come to worry about that, as i mentioned, i have around 10 kg/cm3, and according the manual it should be 14 kg/cm3 ... this might be like this a lot before the overheat problem, but is it something to worry or is normal for these engines to run that low on compression?

if i open the engine and replace the gaskets will it make a difference? I dont know, looks like im looking for an excuse to strip the engine away hehe

Do you know what that is in psi? I can't seem to find a conversion table anywhere. The numbers aren't that important, it's whether or not they are all pretty close to eachother. Low compression is a sign of bad rings leaky valve seats, either one would require tearing the motor apart.

and the 14kg what ever is for a brand new engine im assuming...so as long as yours are all close to the same number u are good.




Steve

Yes, here is the conversion

Standard value, according manual: 1400kpa = 14.0 kg/cm2 = 199psi
Minimum value, (also what i got from my test): 1000kpa = 10.0 kg/cm2 = 142psi

140 psi is what my compression gauge measured , so im just in the min value, thats what im concerned...