Why is my Rover P6 Overheating?

C

Clive_687L

New Member
My overheating problems started when my ’71 2000 SC overheated and deposited its coolant over the road via the radiator overflow tube. We diagnosed thermostat problems and drove home without the thermostat fitted which seemed to prove it.

After fitting a new thermostat the car was good for a couple of drives but then started overheating again. It was at that point I noticed a small leak at the bottom of the radiator. After reading up on possible clogging issues I bought Bars radiator sealant http://tinyurl.com/6gu7l2k as it is not meant to clog. I flushed out the radiator and the hoses (but without managing to open the cylinder block tap) and then put in the sealant along with fresh coolant and water. That appeared to work and after running the engine for a while a test drive worked out fine. The next day however the same overheating problem reappeared and the car once again threw out the coolant via the overflow tube. The new thermostat appears to be working as the top hose gets hot and cold.

I’d like some advice as to what to do now – do I buy a new radiator (I’ve seen one for £109) http://tinyurl.com/5wbf8uy or could the radiator cap be an issue and need to be replaced? Has anyone had any problems like this?

Any help much appreciated.

-Clive.
 
Is it overheating, or just forcing the coolant out from under the cap? I'd test the cap first because, firstly if it's not holding the pressure it will allow coolant to force its way past, and secondly, if that is the case then the lower pressure will cause the coolant to boil earlier, hence making you think its overheating, when in fact it's boiling at a lower temperature than it should. Each lb of pressure in the system raises the boiling point by 1 degree. That and always start with the easiest things first......
 
Thank you very much harveyp6. The temperature gauge goes into the red and up to 100 degrees and the radiator cap appears to be okay but I'll check it again now.
 
I did have a problem once with the temperature sender in my Rover 2000, causing the temperature gauge to read full gauge when it was not hot. Also is the voltage regulator in the instrument cluster operating properly. This regulator reduces the voltage, to a set voltage less than battery voltage, so that the gauges will not be affected as the generator, or alternator cuts in an out. If the voltage regulator is a problem, then I would expect that the petrol gauge would be reading higher than the actual level.

Can you get hold of a non contact infrared thermometer? If you can then you could point that at the head next to the temp sensor and confirm that the temperature is correct.

What sort of coolant are you running. It is possible that if the coolant was changed as some time there could be a compatiblity issue with the coolant which was not drained from the system and this can cause a reaction and a build up sludge. Is the core of you radiator in good condition. If it is then you might want to get the top tank take off, and have the core rodded out. A radiator repair shop can do this, as well as repairing the leak. You would also want to flush out the block, and possibly remove a sideplate, and clean behind the plate.


James.
 
Absolutely, the cap is the place to start. They are cheap, so just replace it anyway. You may not want to hear it, but it sounds like a blown head gasket. These can go in many ways, with different symptoms, such as white exhaust smoke if coolant is going out the exhaust valves, or coolant in the oil, or oil in the coolant if the blow out is by a cylinder. With the cap off the radiator, engine cold, start it up and let it get to operating temperature (NEVER take a radiator cap off a hot radiator, unless you want to be scalded!) If you see bubbles floating by as the coolant moves after warm up, it is also a good indicator that the head gasket is bad. You can actually have the blow out by a cylinder where the piston going up and down pressurizes the coolant system, pushing the coolant out the overflow hose.

You may want to confirm what I have just said with a person familiar to the P-6 as I am in the U.S. and just embarking on my first Rover experience, but I've been a mechanic for a long time, and have worked on engines for a good number of years, mostly V-8's with a pair of heads each!

Start simple, with the cap, and then if that does not solve the problem, continue with the checks. Even a blown head gasket is not a catastrophic issue, and your average guy, with common sense and good advice, not to mention a good set of hand tools can make the repair. Good luck, and post your resolution, please!
 
I've found with my sc that poor timing and fuelling can make a good engine run hot and close to the red. Be worth a quick check before you take the plung and whip the head off.
 
Thanks for all your help and suggestions guys.

M.F. Smith I was worried it was looking like a blown head gasket too. I tried your test and started her up with the radiator cap off and soon I was watching bubbles break at the filler neck. Oh dear. At that point I called up P6 expert Nick Dunning and he came up last week. He did a compression test and surprisingly the results were good, ranging from 140 to just over 150. That ruled out the head gasket. So next we had to start her up and watch the problem in action, so we started her up and waited... and waited... and waited a bit more. Everything worked fine. :eek: We took her on a test drive; everything was okay. :? We let her run some more and nothing happened. Nick was by then pretty sure that she'd suffered from a pretty serious airlock that had worked its way out. It's been about a week since then and she's behaved perfectly! Oh well a happy ending then (hopefully) but not an ending that really gets to the bottom of it. Now on to a bonnet and boot respray...
 
You could of easily had an airlock. When refilling the cooling system, I always loosen the upper heater hose at the heater and slide it off just enough while the engine is running to allow the air out until I get a solid stream of coolant, then tighten the hose back up.

Yours
Vern
 
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