e4yob Posted January 31, 2011 Share Posted January 31, 2011 Hi, I have recently fitted a 3.9 efi auto into my 90, The engie always starts first time and runs nice and smooth.The problem I'm having is that at idle it over heats fairly quickly to the point of boiling over. How ever if I switch the fans on it will sit at about 70c and when driving around it is fine. The cooling system does not over pressurise and I'm not losing any coolant. I do how ever get a fair amount of white ish smoke from the exhaust on start up when cold and lasts for quite a while but then clears. i haven't yet done any tests for head gasket or slipped liner as It's not showing any of the symptoms as such. The motor to me seems to lack power compared to a 3.9 efi rrc I had a few years ago and seems to have way excessive fuel comsumption even for a v8. One thing I did was to fit a new distributor and not have the timing checked. Could it be possible for the timing to be out enough as to cause the over heating but still run ok, or am I looking at the dreaded liner problem. I also fitted a new radiator when I fitted the engine. The water pump is working ok and at the moment there is no thermostat fitted. If any one has had a simular problem or advice it would be great to hear. Many thanks Karl Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted January 31, 2011 Share Posted January 31, 2011 You say 'switch the fans on', radiator or heater? If radiator, you will need to have them switch on and off thermostatically, not like a diesel where you can basically run without one! White smoke on starting is just condensation in the exhaust, nothing to worry about, especially in this weather. If the water system isn't over pressurising you don't have slipped liner/head gasket gone causing the overheating. Timing makes a huge difference to power on the V8s, get it set to 6-9 BTDC and see how it runs. Timing won't make it overheat when idling, more likely at cruise speeds where damage can occur. If when you are driving it around and the coolant is only at 70C you may find that your fuel consumption is bad because it is not warming up properly, it needs to be at least 82C when running really. Other thing to check is the ECU coolant temperature sender, if this fails it will just keep on chucking fuel in because it thinks it is -40C outside I would start by checking the radiator fan(s) whether viscous or electric, water pump, air locks in the cooling system, thermostat -does it have a jiggle pin and is it fitted at the top? Quote Link to comment Share on other sites More sharing options...
e4yob Posted January 31, 2011 Author Share Posted January 31, 2011 Hi thanks for the qiuck reply, I forgot to say I've got twin electric fans fitted on a manual switch as my thermostatic switch broke. so I tend to switch the fans on when the temp gets to about 90c which is only when its at idle or heavy traffic. I've not got a thermostat fitted at the moment. I had heard that a faulty ECU coolent temp sender could cause poor fuel consumption so I'll try a new one of those as well as getting it timing checked. My main concern was the over heating at idle although is fine when the fans are running. Whats the best way to check for an air lock and the best way to bleed it? Quote Link to comment Share on other sites More sharing options...
nicksmelly Posted January 31, 2011 Share Posted January 31, 2011 The overheating at idle could be an air lock. I had a similar problem a few weeks ago on a 3.9. Check that the throttle heater on the plenum is not blocked, as this is the highest point and is where most air collects and gets back to the header tank. I took mine off to check and it was full of rusty crud. Cleaned it out and it has been fine since. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted January 31, 2011 Share Posted January 31, 2011 They can airlock, especially if the stat is non-genuine (doesn't have the little bypass hole). I didn't plumb the plenum heater in on mine. Also you do need the fans to come on before it gets too hot, otherwise they have an uphill struggle. V8's will warm up at idle unlike diesels. Quote Link to comment Share on other sites More sharing options...
e4yob Posted January 31, 2011 Author Share Posted January 31, 2011 Thanks for the replys guy's ive not heard of the throttle heater on the plenum, I'll check that this weekend. And get hold of a new thermostat to put in. i've got two huge electric fans on it which has no probelms cooling it down. I just think it gets hot far too quick. ive got a good few things to check out on it this weekend to keep me out of the way of her in doors lol. Quote Link to comment Share on other sites More sharing options...
e4yob Posted January 31, 2011 Author Share Posted January 31, 2011 thanks for your replys guy's. I've not heard of the throttle heater on the plenum, I'll have a look at that at the weekend. My fans are moe than up to the job of cooling it. If or when it has boiled over when I switch the fans on it brings the temp back to normal really quickly. I just need to get another thermostatic switch as I have a habbit of forgetting to switch the fans on. I think its an age thing lol Anyway I've got more than enough things to keep me out of the way of her in doors at the weekend lol Quote Link to comment Share on other sites More sharing options...
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