Misfiring when hot no more but a new problem.

I last wrote in on Aug 11th about my Freelander 1, 2003. 1.8 that was misfiring when hot. Since then I got bitten by as tick and had long drawn out Lymes Disease and been quiet. However I had the energy to solve the misfiring problem during that time. I got a warning code that the throttle sensor valve was faulty and as it is only a potentiometer and I have cleaned inside many of those over the years in radios and stereos I decided to clean this one. If it didn`t work I would have to replace it anyway. I used normal contact cleaner spray and gentle compressed air to dry it. Did that 4 times and refitted it. It worked. It worked for one month. For some reason when I stalled the engine it decided to go back to playing up. Fitted a new one and problem solved again this time for good I hope. The new one was stiffer than the old one, praps better contacts inside.
When that problem was solved another one showed up. The steel water pipe from the water pump had a rust hole suddenly and the engine lost coolant. The temp gauge did not show that it was overheating. The pipe was replaced, inlet manifold gasket was changed, jiggle pin was checked and system refilled and bled several times. However, when the engine is running and the Torque app. shows the coolant temp is 100 C the expansion tank fills with coolant and the cap releases it. Bubbling can be felt and heard in the top hoses. There is a new set of hoses and thermostat, new expansion tank and cap, the old tank was first tried with a new cap but replaced because of stress cracks. The fan comes on slowly at first at 102 C then speeds up if it gets hotter. There is no bubbling before the temp gets to 100 C. No smell of exhaust in the tank, no watery gunge under the oil filler cap, no white smoke from the exhaust. There used to be a bubbling sound in the heater matrix but that has gone now. This has happened about 7 times now, always at the same temp. The engine can idle for ages and not do it but if I drive it does it faster. I am hoping that I don`t have a blown H.G. as getting that repaired here in Norway would cost more than an arm and a leg. As I have replaced the water pump, timing belt, other belts and tensioners and pulleys earlier this year I don`t want to take that lot off again esp.as winter is here. I will flush the system and I am thinking about putting yet another new thermostat in. Can get Gates ones that start opening at 82 C and see if that would help. Hoping for and would be grateful for suggestions.

It does sound like a HG failure. However, do check everything carefully. Does the coolant level drop? Try bleeding the cooling system again by the two bleed screws on the steel coolant return pipe and the heater pipe. Is the radiator in good condition? Did you fit a good quality coolant pump? Check the thermostat operation or replace it ...

Hearing bubbles does sound like still an air in the system.
Go they the bleed process again then run the engine without the pressure cap fitted, let it reach 85-90c and switch off. There should be no overflow of coolant at this point. Let it cool down for 30 mins then refit the cap and try again, let it reach 95c then stop and cool down completely. Is there any pressure in the system at this point? This would likely point to exhaust gas in the coolant system

htr said:

It does sound like a HG failure. However, do check everything carefully. Does the coolant level drop? Try bleeding the cooling system again by the two bleed screws on the steel coolant return pipe and the heater pipe. Is the radiator in good condition? Did you fit a good quality coolant pump? Check the thermostat operation or replace it ...

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Hello htr, thanks for your reply. Before bleeding the system again I drained and flushed the system in several directions. I began bleeding the system by starting with the lower screw and keeping it open while filling, when coolant ran out I closed it. I did the same for the upper screw. I then topped up, replaced the cap and started the engine. When it got hot I stopped it and opened the screws, lower one first. Topped up and restarted and bled 3 more times. The heater got hot but the temp stayed at 85 C for ages so I went for a run. It then went up to 98 C, the tank started to fill and then at 100 C water blew out of the cap and there was a lot of bubbling sounds from the top hose. The rad fan did not come on this time and it is dusty but in good condition, the pump is a good make and the thermostat is new, it came as an part of an assembly with hoses. Likewise the tank and cap are new as are the heater hoses. I fitted a new temp sensor but had to refit the old one as the new one caused chaos in the fan department. I had no cooling problems until after the steel pipe, the manifold pipe and the valve cover gasket were replaced so if it is not the HG it could be something I have done with the manifold gasket or valve cover gasket. I am 100% sure that everything has been put on the right way around. I just dont understand why no bubbles are seen or heard until about 98 C every time. The engine could stay at 85 C all afternoon if you let it. There is no smell of exhaust in the tank and neither is there any oil in it either, If I am out driving and the tank starts to fill, I park before it blows and the engine ticks over again the tank level drops to more or less normal at about 88C. Just hoping that it is not a head gasket as labour prices over here are horrible. .

When it's hot, are the hoses soft, firm, or rock hard? They should be firm but squeezable

kermit_rr said:

When it's hot, are the hoses soft, firm, or rock hard? They should be firm but squeezable

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Hello kermit_rr, thanks for your replies. I haven't been able to follow your suggestion but when hot the hoses were not rock hard, I was able to squeeze them when I tried to move any air in the system. When I squeezed the hose below the thermostat ,which is new, it was cold even after the blowing off. I have read that because the rad is oversized and so efficient that the hose will be cold under normal use. But then in some cases that is a sign that the stat. has failed shut. I have ordered a new one just in case.

Hi, when you say the temp. gauge didn't show signs of overheating that maybe because the sender unit had no coolant around it to give an accurate reading on the temp. gauge, so I'm afraid it might have HG failure due to overheating even though the temp. reading seemed normal, that is if it's not a trapped air issue.

Andy Warren said:

Hi, when you say the temp. gauge didn't show signs of overheating that maybe because the sender unit had no coolant around it to give an accurate reading on the temp. gauge, so I'm afraid it might have HG failure due to overheating even though the temp. reading seemed normal, that is if it's not a trapped air issue.

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Hello Andy, thanks for your comment. The cars gauge seems to stay horizontal no matter how hot the engine is.. What I should have included was that being underimpressed by the standard temp gauge and interested in following how the engine heats up I plug in one of these code readers using the Torque app.and watch the way the temp fluctuates in different situations. When I can see the app showing 98 C, I jump out and look at the tank, If I switch off the engine before the blowout it calms down, then restart and it can idle for ages at bout 85-90 C and not blow. if I go for a drive it will if I let it. For the temp to show in the app then there must be a temp. reading from the sensor getting to the ECU which is where this app is getting its info from. What baffles me is that there is no bubbles coming into the tank all the time the engine is getting hot. It is only from 98 C up. If the HG is gone wouldn`t there be a steady stream of bubbles into the tank while the engine is running. As I have said before, there is no white smoke, gunge in the engine or smell of exhaust in the tank. I am trying to think of everything it might be except blown HG. The cost of replacing one at a workshop is horrible. What if the head is removed and the gasket was healthy all the time. At least I dont have to replace the water pump, timing belt tensioner, other tensioners, belts and pulleys, that was done about 1500kms before all this started.

You need to get the coolant'sniff tested'for peace of mind. This will tell you accurately if there is any exhaust gas present.
I had a cracked block that only leaked over around 85c

Hi, I'm not sure when the thermostat opens on the 1.8 but if it doesn't open fully until around 85-87 degrees then it might be containing the pressure (especially if it's a bit sticky) until it opens fully then the sudden rush of pressure pushes coolant out of the expansion tank. I'll keep my fingers crossed for you that it has an air lock some where. I remember when the Honda CBR1000F first came out in the late 80's & after draining the coolant & refilling it, if you didn't bled the system properly then it would throw the coolant out, Honda even sent a bulletin out on the correct procedure, as us mechanics were having trouble but you basically filled the system very slowly & squeezed each hose starting at the lowest & if you could raise the front slightly that helped as the radiator cap was just behind the steering stem nut on the top yoke, best of luck.