overheating problem

Hey guys,

I've got a 81 mk1 1600 gti and i'm having problems with the cooling system. kinda long story so far but i'll try to cut it down!

I fitted a recon engine from volkspares (vege) along with a new rad, new water pump, new stat and new silicone hoses. everything was going great, ran it in below 3000 for 1000 miles etc and took it gentle for a while after so everything bedded in nicely.

but just lately it started to overheat when sitting in traffic, then after a few weeks it started to overheat pretty much straight away from cold, 10 mins-ish (even when it was -3 degrees outside! )    :?  

The engine apeared to be running fine but was on the very top end of the gauge. I tried removing any airlocks (heater on warm and run up with out cap on etc), checking the timing, a new fan switch, a new temp sender, new thermo time switch and voltage regulator for the clocks and this lot didn't change anything

I checked the gauge in the clocks with a variable resistor and everything appeared pretty much as the haynes manual shows which suggested the engine was actually overheating, I managed to borrow a temp gauge from a mate and clamped the thermocouple in the top hose by the rad, this read 110 degrees and the fan didn't cut in.
 so it appears the engine is deff overheating, I tried a new expansion tank cap and also checked the thermostat opened okay in boiling water, also that the water pump impeller wasn't spinning freely on the end of the shaft, ran a hose pipe through all the major components which were all clear and unblocked, I then refitted it with fresh antifreeze but still had no joy.

I'm running out of ideas of things it could be (and losing the will to live    ) I'm hoping it's not the head gasket, there's no mayo on the filler cap, it's not losing any oil and doesn't appear to be losing any water either?

Anyone got any ideas before i torch the Sodding thing!! :dontknow:

Thanks,

Tim

Did you change the oil after the running in period?

It may be full of the small particles of metal that have been worn off by running in, and therefore not lubricating as well - hence making the car run hot.

The cooling system passes water through an oil cooler above the oil filter, as well as through the channels in the engine itself, although some golfs have a separate radiator for the oil system.

If your car has an MFA, you should be able to monitor the oil temperature as the car warms up. If the oil hits above 105/110 degrees C then it's running a tad hot.

I believe there are also different ratings of thermostat, so you may have a hot one that doesn't open until the engine temp is hitting the top of the gauge.

Hope this helps


AliCabrio

If the fan is not cutting in (should do around 95 degrees) then either the fan, switch or wiring is at fault.

Run power direct to the fan to see if it spins
Put a meter across the switch when hot to see if the switch is working
Check you have 12v at the switch and that the motor is earthed

Not necissarily in that order!

Cheers

Rich

Does it overheat when moving or just when stationary?

To test the wiring and fan touch the wires from the switch together, the fan should run. Beware that this will work even without the keys in the ignition!

cheers for the replies guys,

I changed the oil n filter @ 1000 miles, mines got a separate oil cooler by the side of the rad, the oil seems to be running about 80-90ish ( i have checked its not something daft like i've plummed the oil up to the water temp sender too as the relevant gauge goes up down etc when i connect it to earth or disconnect it!)
I've not got mfa thou, which is why i had to borrow a temp gauge with a scale on it to know how hot the water was getting as the dash gauge is a bit of a chocolate fireguard with no figures on it.
also, VW say there's only one type of thermostat, 87 degrees? is this right? it matches the haynes book of lies but suppose that could be wrong?


I tried the fan too but forgot to write it on! tried to reduce the size as it felt like i'd written a book not a post!  
i've checked the fan does work by linking the contacts, also added a switch to turn it manually on to try and help things.
although it doesn't seem to be getting that hot down near the bottom corner of the rad where the switch is so maybe the stat isn't opening when it should?

It overheats either staitionary or while moving, but it does get a bit hotter while staitionary, i guess because the fan doesn't know to cut in!  :dontknow:
not driving it at the minute thou cause i don't wanna do any damage to it   :cry:

can't even afford to torch it cause of the price of petrol these days!!!

Tim

would running it without the thermostat (not permanently!) harm anything? I'd imagine it'd take longer to warm up but may identify if it's the stat?

I seem to remember reading somewhere about making sure you put the thermostat in with the small hole at the top, to make sure it doesn't block up, and to avoid air locks.

As a last desperate measure you could just take the thermostat out. Just means the car will take longer to heat up.

Check the fan belt tension - if it's a bit loose, it may not be turning the water pump enought to circulate the coolant - although I'm probably grasping at straws with that suggestion.

Ali

didn' know there was a small hole in the stat?
I've been grasping at straws for weeks! starting to run out of straws now!
 
…hope its not something daft!  :doh:

from past experience the faults that cannot be found are the easiest to fix! (once youve found it!)

Good Luck

yeah, know what you mean Dougelove, pulling my hair out here!

A mate suggested checking the regulater bit on the oil filter housing that feeds the oil cooler but everything there seems okay too, all assembled correctly, free operation etc.    

Hi Guys

I had a similar problem with my Mk1 1.8 GTI. The problem could come from the water thermostat, on my car the temperature gauge was always hovering around the hot end of the gauge. To cool things down a bit I cut down the thermostat spring (I took out half a coil with my Dremel). Less pressure on the opening means the water passes through the radiator at a lower temperature, keeping the engine cooler. This is a last chance measure though. Make sure the basics are working. Touch the thermostat wires together to make sure the fan works, remove the thermo switch from the radiator and place in a tin of water, boil the water with a blow torch to make sure the fan (and therefore thermoswitch) works. And finally remove the radiator and connect a hose up and give it a good blast in all three openings, you'd be amazed how much gunk collects in there over time.

One final check, are you sure you have the correct new radiator? I bought my car and had dreadful overheating problems for ages. It wasn't until I saw another Mk1 did I realise someone had put a 1.3 radiator in! No wonder the engine was struggling to keep cool!

cheers for the advice Jochan, it's not quite come to the cutting spings in half stage yet!

Have you (or anyone else) got any photo's or dimensions of a proper size rad? maybe I was given the wrong one?   :dontknow:

tim

Also check to make sure the small recirc water pipe from the top of the rad to the expansion tank is not blocked, as these wil lalso cause the car to overheat as it needs this small bore pipe to circulate the water, easily checked by takig the cap off the expansion tank, start the engine and make sur eyou have a small stream of water coming out of the hole into the tank (bit like those piddling little boy statues you see  ops: )

Hey guys, sorry to drag this old post up but I've still not sorted my problem. (got lazy over winter cause it was too cold!)
I've ran out of ideas (and motivation  :cry: ) so i guess it time to call an expert….
Anyone know a good garage somewhere near Leicester that may be able to fix/investigate it?

or has anyone got any other ideas? (i've consdered the scrapyard…..)

cheers,

tim