Strange overheating problem?

Post by **hi_tower** » 04 Aug 2007, 19:46

Hi All,
This my first post on this forum although I have been lurking around here for a while. Today I picked up my 84 t25 caravelle (1.9 petrol I think, 78ps whatever that means). I bought it with a very strange overheating problem. When I got stuck in traffic the engine began to overheat and boil like a kettle. I could see large bubbles rising into the header tank and the gauge went all the way over to the right hand side, although no coolant over flowed. I stopped and let everything cool down. When I got onto the motorway the temp dropped right down to cold and the faster I went the lower the temp became? The p/o has had the water pump replaced and I can see clean new gaskets on the manifold so Im wondering if the heads have been off also. Oh also the oil light began to flicker when the temp got real high. Anyone hazard a guess as to what I should have a look at first? Ive done a few searches and cant find an answer for this odd problem?

Post by **Plasticman** » 04 Aug 2007, 21:57

As it cools with forward motion (on m'way)this would indicate air flow through the rad',= cooling fans not cutting in=switch on rad bu**ered or fan ditto.

Remove grill and take plug of rad switch(right hand side as looking from front) get a meter and find a live if any and with a bit of wire connect to one of the other terminals on same plug, if no meter then keep pairing up , you should get the fan running on 2 speeds, if it does then rad switch is U/S, if not then supply to same or fan itself is U/S
Mike

Post by **syncronaut** » 04 Aug 2007, 22:37

Quick fix. Check fuse number one for fan (first on left of fuse box)
Also note that fan thermo switch some times doesnt work if hot water doesnt reach rad due to airlock in system. Check air bleed procedure as many people dont really know how to bleed these beasts after carrying out work on cooling system.
If sever overheating taken place, get a compression check done. This will indicate if head gasket seal compromised.
Oil light flickering? Hot engine- thinning oil due to hotter temp, hence lower oil pressure. Dirty oil filter restricting flow Possible faulty oil pressure sender. Low oil level. Worst case scenario- oil pump failing. Check oil condition. If in doubt replace oil with new and fit new filter. You know it makes sense
Good luck
Syncronaut

Post by **billy739** » 04 Aug 2007, 23:10

also see if the front/rear pipes seem to get warm from cold, suggesting the thermostat is faulty,this would give the fault of the temp dropping to cold,not a normal 'middle gauge' reading which is where it should sit at motorway speed

Post by **hi_tower** » 05 Aug 2007, 08:32

Oh I forgot to mention, the p/o has installed a switch on the dash for the fan so I presume the switch in the rad needs replacing. So I had the fan running from the dash switch as soon as the traffic slowed down but this didnt stop the temp from rising very quickly. When I stopped the rad was hot but quite quickly went cold, whilst the engine remained red hot. I think I will try running it without the thermostat today and see if that makes any difference.

Post by **hi_tower** » 05 Aug 2007, 09:47

Looked at the engine this morning when every thing is cold and one of the big water hoses has gone flat with suction inside the system?

Post by **Westy.Club.Joker** » 05 Aug 2007, 19:07

Sounds like you need a new GENUINE VW tank pressure cap (blue one with one valve inside)

Post by **trickydicky** » 06 Aug 2007, 03:16

Could be an air lock, what is your heater in the cab doing?

Post by **hi_tower** » 06 Aug 2007, 06:25

the heater was hot i think. not too sure about when it was overheating as i was in a bit of a flap trying to get out of the traffic jam down a side st.

Post by **ermie571** » 06 Aug 2007, 07:42

also see if the front/rear pipes seem to get warm from cold, suggesting the thermostat is faulty,this would give the fault of the temp dropping to cold,not a normal 'middle gauge' reading which is where it should sit at motorway speed

ummm billy could you explain a bit more......our camper's temp guage can fall to nealy the bottom of normal going down a hill, and can run quite cool (in the first quarter of the temp guage) on the motorway. Not sure what you mean by "get warm from cold"? - should they not be warm, then?

Sorry if being thick, but I did not appreciate that the needle droppin like that was a fault particularly.

Fan comes on quite late, but when it does it cools the engine nicely.

Post by **trickydicky** » 06 Aug 2007, 11:52

I had loads of trouble with mine with air in the system.
On the motorway in fourth it actually ran cooler, I first thought after the flush I did I had blocked the rad. One new rad later I went through the bleeding process again.
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