I don't know about the diesel, but at least for the petrol, the gauge should never go beyond the 12-o'clock no matter the load. The only movement you should see from the gauge is when it's warming up from cold, and it will also drop quite a bit if you roll down a long hill with your foot off the throttle and the outside temperature isn't very high. Unless you have some sort of instrument failure, it would seem you have a problem that needs fixing.
Overheat - Am I missing something
- Thread starter timh1970
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I don't know about the diesel, but at least for the petrol, the gauge should never go beyond the 12-o'clock no matter the load. The only movement you should see from the gauge is when it's warming up from cold, and it will also drop quite a bit if you roll down a long hill with your foot off the throttle and the outside temperature isn't very high. Unless you have some sort of instrument failure, it would seem you have a problem that needs fixing.
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If the head was cracked or the gasket on it's way home you would get a lot more than a brief hiss with the engine hot as you opened the pressure cap believe me. Hot water would be ejected as the gas in the cooling system expanded. Stick it on diag and check the modulation and function of the timing solenoid. Head bolts don't come loose.
Datatek
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That was certainly not the case on my scrapper, all the pressure went out of an exhaust port and various other places, there was bugger all pressure in the cooling system.
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Heads crack in different places if the head cracks from cylinder to water jacket or the gasket blows from cylinder to water jacket you would get gas in the coolant and the system would pressurise PDQ. On opening the pressure cap you would get coolant ejected as the gas expands. Certainly so if the engine is hot. If it cracks between the water jacket and exhaust, coolant will go out the back. This guy has no coolant leak or he has not mentioned one, and no excessive pressure in cooling system therefore i would be surprised if head is cracked or gasket is blowing. Even if he has fitted a non vented thermostat and there is air trapped in the head i would also expect coolant to be ejected when the cap was removed or even when the engine is running. Bit of a puzzler really. Coolant will be at 6 or 7 PSI or so with engine hot. That would give a hiss as the cap was removed, any air or gas trapped in system would certainly cause coolant to be ejected if there was a lot in or at the very least a serious burp from the header tank.
Modulation is sitting at around 47 when idle but it has been adjusted to compensate for a bit of timing chain stretch if that makes a difference.
If you rev it from idle you get particulate type black smoke out of the exhaust for a brief period but it clears up pretty quick.
I think that pressure when hot would be around 7 psi. The hoses seem quite hard, but there is not a lot of pressure when you take the cap off. Even after the big hill climb up snake pass when I dived out of the car and opened the cap straight away at 105 degrees it hissed little just a little more than opening a fresh pop bottle.
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Modulation is good at 47% only 3% from ideal. You mean the pump static timing has been adjusted? Only real way to check pressure build up is with a static test rig. A rapid rise in pressure would indicate something leaking into the coolant. But that does not seem to be the case, how are you measuring the temp? The temp will rise as the engine is loaded. Are you just measuring temp with something like Nanocom or is the gauge needle going over centre? If you are measuring with diag but the gauge is staying more or less stable you don't have a problem. If the gauge is moving a lot over centre at 105 degrees maybe you have a duff sender.
Yes, pump static timing has been adjusted but only a little (it hasn't been moved far enough to cause the hot start issue yet). Temp is being measured with nanocom. On the gauge the needle will only go over the centre if under heavy load (not necessarily fast driving, but very steep hills will send it up). It is not bad now on most roads, but I believe that it will be with a caravan on the back of it (which will be its purpose in life when I get it right).
The viscous fan is kicking in when the temp sensor is around 96 degrees (so I guess that will be about 80degrees in the middle of the radiator near the bimetal strip)
It is certainly worth trying the sender before taking the head off so I will give it a go.
The only other thing about this car at the moment is that there is no AC condenser rad on it. I can't see this having any effect, if anything I would expect it to improve the airflow and subsequently cool better.
A row of fins is missing off the oil cooler (I have a new one on order) but the mean time between increased load and increased temperature is too short for it to be an oil cooling issue.
It was a pup was this car when I bought it so it has had a load of parts on it. It's had the turbo reconditioned and the injectors reconditioned and the whole of the cooling system replaced - It is one of them now where I have spent too much money on it to sell it and get another (it is going to want a gearbox at some point, 'cos it's slipping a bit in 3rd, but it will do for now and they are cheap enough on ebay).
The viscous fan is kicking in when the temp sensor is around 96 degrees (so I guess that will be about 80degrees in the middle of the radiator near the bimetal strip)
It is certainly worth trying the sender before taking the head off so I will give it a go.
The only other thing about this car at the moment is that there is no AC condenser rad on it. I can't see this having any effect, if anything I would expect it to improve the airflow and subsequently cool better.
A row of fins is missing off the oil cooler (I have a new one on order) but the mean time between increased load and increased temperature is too short for it to be an oil cooling issue.
It was a pup was this car when I bought it so it has had a load of parts on it. It's had the turbo reconditioned and the injectors reconditioned and the whole of the cooling system replaced - It is one of them now where I have spent too much money on it to sell it and get another (it is going to want a gearbox at some point, 'cos it's slipping a bit in 3rd, but it will do for now and they are cheap enough on ebay).
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105 degrees is where the modification put on 1999 and on cars would start the aircon fans to assist cooling. Does the heater work properly if the matrix was clogged that would make a difference. Take the head off by all means if you think you need to, but nothing i have heard from you points in that direction at the moment.
This is a 97, the heater matrix gets very hot so I guess it isn't clogged.
As they did a mod to kick the aircon fans in at 105 did they have issues with the early ones overheating when they came out of the factory? If so then it is probably as good as it gets and I am p'sing up hill in wind unless I can do the mod to this one. That would fit perfectly with what is happening because if I put the heater on full, even pounding it up a hill, it stays within tolerance; but I just could not believe that they would let 60 grand cars go out of the factory that would overheat under heavy load (especially a towing car).
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The petrol engines have always had this facility to aid cooling at times of high engine load in hot conditions. For example if you have just come off a motorway and are sitting at lights with the aircon on. The engine is idling so not circulating coolant to get rid of latent heat so at a preset temp the aircon fans come on to assist the viscous. This was introduced on the diesels for MY 1999. If it never goes above 105 i can't see a problem to be honest. If everybody drove around with a Nanocom connected it would clog the site up.
I always put the heater on when it gets to 105 because I don't want to risk it going any higher, but it would if I gave it the opportunity. When I put the heater on it cools down again.Coming off a motorway is fine, it does not overheat. It is literally only when going up a steep hill that there is a problem.
Datatek
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If all the cooling system is good, I would still suspect the head, my scrapper was just like that, the previous owner replaced everything including the head gasket to no avail. I bought it as a scrapper.
Coming off a motorway is fine, it does not overheat. It is literally only when going up a steep hill that there is a problem.
However, if you can control the overheat using the heater, it may still be that you have a problem with the cooling system, fan, stat, RAD etc. You could try running without the stat.
Gauge never goes past 12 o'clock on mine.
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Coming off a motorway is fine, it does not overheat. It is literally only when going up a steep hill that there is a problem.
You have checked that you don't have any brakes binding i take it?
tomcat59alan
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Course he may weigh over 35 stone like the fat bitch on my flight home. She had to sit in the back row otherwise we wouldn't have got the nose wheel off the ground.
At idle for an hour after a fully warmed up run it sat at 95.0 occasionally rising to 95.7 and then going back down again as the viscous fan kicks in and out. Driving around relatively flat country lanes it would go up to 97.8 give or take which I reckon is perfectly normal.
I am going to steam clean the intercooler and replace the oil cooler before going any further just to see if that makes a difference as it could be a hot oil issue. I've noticed that from cold when the water heats up to the point where the stat if fully open it sits at about 93 and stays there. As the oil temperature rises (once it has been on a run), it sits at 95 so the temperature of the oil must have some impact on the temperature of the water. Perhaps it is as simple as that 1 row of fins missing off the bottom of the oil rad that is causing the problem.
I am relutant to believe it is the head as I am not losing water and there is no pressure in the coolant system and no dreaded globules on the oil filler cap or the expansion bottle cap.
I had a renault diesel a few years ago that was almost identical to this and that did turn out to be the head so there is still a possibility but there was a fair bit of pressure in the water system with that one.
Whatever it is is only very minor overheating, but it would stop it from reliably towing a caravan.
Wouldn't taking the stat out cause it to overheat because it would not be able to block off the bypass circuit?
I hadn't, I'll have a look tomorrow.
Datatek
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No stat it should run cold most of the time.
Ok, after a little trip out over the M62 with the trailer tent on doing 50 - 56mph max the temp got to 106.6 on the hills before I hit the heaters to help it a bit and it dropped down to 93 when the road leveled off.
I am now almost certain that this is a head issue; hopefully the gasket, if not then a cracked head is possible. Does anybody know anywhere in or around Lancashire that tests them for fractures?
I am now almost certain that this is a head issue; hopefully the gasket, if not then a cracked head is possible. Does anybody know anywhere in or around Lancashire that tests them for fractures?
Datatek
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Sadly, head is more likely than gasket.
I think you might be right, it is too consistent and requires too high a load for it to be likely to be the gasket. To give you some idea I went over the same stretch of motorway today without the trailer tent and a fair bit faster but the needle never moved. As soon as you attach the trailer tent (which I can pull at 70+ with a 1994 saab 9000 auto without issue) it will not go up the hills on the M62 without overheating even at 50.
The only thing that is bugging me is that it is not losing any fluids and there is enough, but never too much pressure in the expansion bottle.
With the potential of the head being gone and the gearbox on its way out though I think it is time to look for another collection of parts in the shape of a car and hope that lightning does not strike in the same place twice.
