Forum:
Hi all,
I have fairly recently bought 3 Daihatsu Sportraks, which me and a group of friends are taking on a rally to Mongolia. I've been working on them quite a bit, but still have an overheating problem with one of them a month b4 we go which is not good!
I noticed the problem when I first drove the car home, it was fine on slow roads, but at 70mph I realised the temperature gauge was nearly at the top. I got the windows open, and the heating on and it came down and stabilised. Now when I first looked at the car, there was very slight evidence of mayonaise in the filler cap, but after this longer journey it was all gone. I have found on previous cars that lost of short journeys can cause this, not always head gasket.
Anyway I also noticed what looked like evidence of some water having been sprayed out the top of the radiator when I got back.
Since then I have checked the following:
Radiator - the fins are clean (can see through it), I have also had it off and water flows through in both directions no problem
Water pump - haven't directly checked, but when engine is revved with rad cap off, the water level surges up and spills over. Also since using heat matrix helped cooling, I think water pump should be ok
Thermostat - old one was only opening 4mm, not 8mm it says in book (in fact although part of it moved, I don't think it was opening at all). I have replaced it with one I have tested which works from Milner, with airlock widget at top (see pic: http://www.milneroffroad.com/img/productImages/8846.jpg). 
I have flushed the system with water 3 times, no funny lumps came out and water was clean.
There was no oil in the coolant when I first drained it. There is no evidence of water in the oil in the filler cap or dipstick. The amount of steam coming out the exhaust after starting does not seem to be excessive and it goes away when warm.
When I found the problem with the thermostat, I thought this would be problem solved. However with the car stationary sat at 3-4k rpm, the water temp dial climbs all way to top eventually and it looks like water is boiling off into expansion tank.
Another problem I found was hoses for vacuum advance were not connected, I have reconnected these and hoped that the lack of advance might be causing the overheating, but no luck, still same as before.
So I'm a bit stumped! Perhaps it could be timing, but I would expect engine to be rough and it seems fine. Perhaps head gasket, so exhaust gases going into water, but would be very specific failure as no water/oil mixing and no excessive water going into exhaust.
The only other thing I've noticed is that on one of the other cars, when u sit at 3-4k rpm the fan seems to spin fairly slowly all the time, but then some sort of clutch engages and it really goes for it, whereas this doesn't happen on the problem car.
Anyway, any help with this would be much appreciated, as it causing me some right grief. At this rate, I may even have to mount the heater matrix near the front as a second radiator! Is it worth me trying without the thermostat in, would I be able to get a seal?
Cheers
Andy
Thermostat and sniff for fumes ..........
Andy.
I suspect you have fitted the wrong type of thermostat. Sporty takes a much longer depth thermostat that reaches further into the cylinder block. Short thermostat will not open correctly and Sporty will overheat.
You could try temporarily removing the thermostat and refit with only the housing. Dont overtighten the nuts ...5lbs max. Also use a gasket sealent. If it runs OK without overheating then go for the correct thermostat which will cost about £20.
If your rad/overflow is loosing water then it could be a blown headgasket. I am suspicious of water boiling in the overflow reservoir. Sniff inside the reservoir whilst the engine is running hot... can you smell exhaust fumes? If 'yes' then cylinder head gas is escaping into the coolant indicating blown gasket etc.
Replies
Hi guys,
Thanks for all the replies. I forgot to mention I have replaced the rad cap and that no longer leaks (one of the seals was nackered on the old one) and I believe the system is pressurising fine.
So is the best place to get a thermostat from a Daihatsu dealer? I think I'll try running it without first, with some sealant to see if that helps. This could even be a permanent solution since I'll be driving through bloody hot countries!
One of the guys at work suggested we pressurise the water system with the air line at work and use a gauge to see if the pressure is maintained. I guess other than that it might be worth me doing a compression test on the cylinders? I think I've got a tester somewhere...
I haven't tried sniffing in the water system, but inside the oil filler cap it did smell a bit exhaust fumey, but that could be valve clearances I guess.
Cheers
Andy
Heated
Agree with Mace, this problem appears to be the head gasket on its way out, at high engine revs it is possible to get a slight leak of gases into the cooling system, at lower revs it does not quite develop enough pressure to cause a leak.
Mayonaise can develop due to vehicles standing for periods of time then only doing short journeys, the oil does not get hot enough to evaporate the water in it, this is particularly noticeable in winter or wet conditions.
OVERHEATING SPORTY
The spray of water at the top may be the seal on the Rad cap. These go over time, sometimes quite short and the after market replacements are worse, my opinion.
I have a new rad. and began, last week to lose water. I watched a constant drip from the rear of the cap as the water heated. This was picked up by the fan and sprayed over the front and top of the engine. I found an old original which I had removed when I obtained the sparkling new cap, problem solved.
You can seal the cap temp. with polythene and see if that cures the problem and you can check that the system is pressuring by feeling the hoses once hot. It is surprising how much you can loose through the cap and of course at the same time the system will boil off because it is not pressurised.
OLDMINIMAN
M J Young
Rad cap
Rad cap seal ......... cut a seal from a piece of rubber inner tube. Also slightly squash the caps lugs so it fits tight onto the radiator. Polythene goes brittle and splits.
This will not be the cause of the overheating problem but certainly the cause of coolant found around the cap.
Update
Right I've just tried running the car with no thermostat, using a gasket sealant. Obviously took a bit longer to reach temp, but then overheated in the same way as before! I also spent some time expelling all the air from the system but that made no difference either. I have checked the spark plugs and they seem to be a light brown which I believe is normal, so I don't think there's anything wrong with the combustion.
I have two more things to try:
1) Cylinder compression test to check for head gasket problems, although if valve clearances are incorrect I could get a red herring here
2) Get some tax/insurance and take it for a good drive. The initial overheating was on motorway, but recent tests have been stationary at about 3k rpm. Since the fan doesn't appear to speed up with engine revs this could be an additional problem, and it might be fine with a good airflow over the radiator. Is there any common problems with the viscous coupling?
Fan
Viscous fan will switch on at a given temperature whether the car is standing still or doing 100mph. Dont expect it to speed up in proportion to increasing revs. Try checking the fan is working : the switch could be faulty. Remove the wires and supply the fan with 12v direct. I recollect the switch is on the earth side of the supply, so try fitting a temp earh direct to the fan. I will look on my CD Sporty repair/maintainence to see how fans should be tested.
Removing the thermostat completely will reduce mpg.
A cylinder head compression test will indicate if the head gasket is leaking. Normally gas leaks into the coolant, oilways, or both.I would anticipate overheating will expel coolant from the reservoir - you do not say if the coolant requires frequent top-up.
Message me with your email and when I have a few minutes spare will look if any diagrams/info on the CD will be of help.
I have the Sportrak workshop
I have the Sportrak workshop manual, but unfotunately in the cooling section there seems to be no mention of dealing with fan problems! As far as I'm aware the fan has no electrical connections, it is driven by a belt off the crankshaft, but has a fluid coupling with a bimetal gauge which helps to engage/disengage the coupling dependant on temperature. I think as the coupling heats up, the bimetal gauge closes a valve which reduces the oil gap between plates and so makes the fan spin quicker.
I have a feeling this is not working, since the fan in this car behaves quite differently to the other two Sportraks I have, so I'm gonna try swapping one over to see what happens.
I haven't been driving the car much, so can't say if the coolant needs frequent topping up, but it doesn't appear to be going down much in the short engine runs I have been doing.
Fan
Just read section on sporty viscous fan. No electrical connections. AT 70C it has two stage operation. If you have a spare then exchange the fan and try again. Also check the engine timing - incorrect causes engine to overheat.
Further update
The plot thickens!
Right I have now changed the fan over from one of the other cars (Car 3) which I know isn't overheating and it made no difference. Even when the problem car (Car 1) gets hot, the new fan still doesn't kick in properly. I have also put the fan that came off problem Car 1 onto the other good Car 3 and it works on that car!! When the good Car 3 gets up to temp, the fan spins much harder when the engine is revved, unlike on the problem Car 1 where it doesn't. So basically both fans are fine, and I have also made sure that both fan belts are tight and not slipping.
I was going to check the temp sender, but I have checked the temperatures at the top of the radiators with a thermometer. When both cars gauges sit at about 11o'clock on the dial, the thermometer (taped to top of rad near pipe entry) read 50 degrees. The good Car 3 gauge and temp didn't really go up from here, whatever happened. However the guage in problem Car 1 keeps going up if the revs are brought over about 2.5k rpm. Once up near the top of the gauge, the thermometer reading was about 75 degrees, then it felt like water in the system was starting to boil. Didn't actually take thermometer readings of the water directly as I didn't wanna get sprayed with hot water, but the problem Car 1 is definitely overheating!
However even when it gets this hot, the fan still doesn't kick in properly, so the bimetal gauge on the front of the fan which controls how hard it spins can't be getting hot. For this to happen, I think there must be a block in that particular portion of the radiator. Assuming that the bimetal gauge is activated by heat from the radiator and not from the shaft of the water pump that it runs on. In fact it can't be off the water pump region heat, as this is much hotter on the problem Car 1, so the fan would spin hard!
I originally checked the flow through the radiator and it seemed to be fine, but if it was only blocked in the middle portion I guess this would still happen. Once the engine was really hot I switched off and felt the radiator after a while. It seemed to get pretty hot in most places except the region near the middle of the fan, so it may well be blocked. I was hoping that doing the same on the good Car 3 would show that the whole radiator felt warm after stopping the engine, but to be honest it hardly gets warm at all!
I've also done a compression test on the problem Car 1, got 13.2 bar on cylinders 1 to 3 and 13.4 bar on cylinder 4, so I doubt I have any head gasket problems.
So I think my latest theory is that the radiator is blocked in the middle, but if anyone has any thoughts on whether this is likely to be correct or not, please let me know! Such a nightmare!
Check it out ........
Your assumption might be correct. If the car is getting old and has not had a regular change of coolant or correct antifreeze mix, then the radiator could indeed be blocked. I would expect a 10year old radiator is in need of a recore. The vertical tubes inside the readiator are very narrow and can block with particles. You will need to remove the radiator and get it tested. I am certain there will be a local MotorRad or similar in your area. If the radiatoris blocked get it recored ... cost is approx £100. Recore is as good as new.
You could try a radiator flush. However if the radiator is old then you could be wasting both money and time. The sensible solution is to remove the radiator and get it checked over. Eliminate the possibility of radiator blockage .... cheaper to do so now rather than have a split radiator miles from civilisation.
PS .... the bottom hose is a pig to remove. Take care not to danage the hose!
Got it!
It was the radiator after all, was blocked in the region just in front of the fan! Thanks for all your help guys.
Eventually ...........
Nice work mocod. We will send you our bill + vat ! lol
over heating
i have the same problem with mine but some times it miss fires if you hold it at 2k the missfire goes and all is normal again but if i go above 3k you can hear bubbles in the heater matrix i think mine is haead gaskit but like yours it fine for short trips around town but if ii gun it it starts messing around its been like it for a year now so iam going to do the head next week and see what happens
over heating
i have the same problem with mine but some times it miss fires if you hold it at 2k the missfire goes and all is normal again but if i go above 3k you can hear bubbles in the heater matrix i think mine is haead gaskit but like yours it fine for short trips around town but if ii gun it it starts messing around its been like it for a year now so iam going to do the head next week and see what happens