Overheating? - Page 3

paulh260260 · 15th March 2021, 21:20

Quote:

Originally Posted by SD1too

Hi Paul,

Yes, that's helped my understanding but I still cannot work out what's going on with your cooling system.

First of all the top hose should be almost too hot to touch, not just "warm". Also don't expect this hose to be firm. The pressurisation is mild, only 15 psi above atmospheric pressure at the most.

This is bizarre! I have to ask, is this a car with problems that you've just bought or has this overheating recently occurred on an otherwise reliable engine? Has K-seal been administered?

Simon

Hi Simon

Maybe the fact that it is idling might be giving false "readings" I have a very short journey to make tomorrow morning let me try the hoses when I finish the journey maybe they will be more as expected then.

As for previous problems I've had the car for just over a year, bought from a local dealer who's been around for donkeys years. Also I've got most of the paperwork showing regular annual servicing up to a few years ago then loads of receipts for parts and other work ( eg brakes, exhaust tyres etc).

Nothing that suggest any major issue, I even specifically looked for a replaced thermostat as its so old but nothing.

Its been a great runner no lack of power or starting issues at all.

Until the overheating problem I had been running it with failed low speed fan for a month or two over the winter when i was unable to fix it. I monitored the coolant levels daily and kept the air con off. The journeys were maybe 4 miles each way per day, 2 miles on clear a roads 2 miles on motorway.

At that point the temp never exceeded 100, but in the last two weeks it started to climb so I decided to swap out the fan and we are now here. Have I damaged the engine by leaving the fan off?

I've personally never used K seal but I haven't clue if it has been used in the past.

Paul

Ducati750cc · 15th March 2021, 23:14

The only thing that hasn't been mentioned and it is quite rare but not unknown on any engine, is that the impeller is loose on the water pump shaft, some cooling is attained when this happens but only by thermosyphoning, however when this does happen it is normally accompanied by a quite drastic temperature and pressure rise with the cap venting pressure and water, but this doesn't appear to be happening to yours.

It's difficult to prove water movement/flow ( not pressure ) by the pump on many engines, nothing to see in most cases, but one way ( easier with vehicles with a separate remote expansion tank ) is to check, when cold and the cap is off, to see if water is flowing through the small de-gas pipe into the tank, just a dribble at idle and as the engine is revved the flow should increase and proves the pump is working.

More difficult to see when the de-gas pipe enters the radiator top tank.

My 75's are diesels, I'm presuming, but don't know, that your rad is the same as mine and the de-gas pipe fits onto a spigot just below the rad cap.

If you remove the cap you should see a small hole just below the bottom seat of the cap in line with the spigot and water and possibly air should be seen issuing from this hole increasing as revs rise, if you disconnect the de-gas pipe you should be able to gently pass a piece of wire through the hole to ensure it's clear and able to do its job which is to remove any air bubbles in the system, if I get chance tomorrow I'll see if I can get some photo's of mine.

I admit the above is a remote scenario but it's looking at clutching at straws time.

A quick but pertinent question, have you done a correct cooling system pressure check which starts with a cold engine, the first test is the cap to see if it vents at the correct pressure and having vented retains pressure just below its lift pressure.

Next is to pressurise the cooling system to just above the cap lift pressure, check for leaks and that there is no pressure drop over time.

Next, pressure tester still fitted but previous test pressure released, engine started and pressure and temperature monitored ( increased idle speed sometimes needed ) until the fan comes on, at this point a healthy system will show pressure below the lift pressure of the cap and as the fan runs temp and pressure drops till the fan switches off.

Sorry for the lengthy post, but there's a reason for your problem and sometimes throwing all the possibilities in the the pot and giving it a good shake find a solution.

paulh260260 · 16th March 2021, 11:28

Quote:

Originally Posted by paulh260260

Hi Simon

Maybe the fact that it is idling might be giving false "readings" I have a very short journey to make tomorrow morning let me try the hoses when I finish the journey maybe they will be more as expected then.

As for previous problems I've had the car for just over a year, bought from a local dealer who's been around for donkeys years. Also I've got most of the paperwork showing regular annual servicing up to a few years ago then loads of receipts for parts and other work ( eg brakes, exhaust tyres etc).

Nothing that suggest any major issue, I even specifically looked for a replaced thermostat as its so old but nothing.

Its been a great runner no lack of power or starting issues at all.

Until the overheating problem I had been running it with failed low speed fan for a month or two over the winter when i was unable to fix it. I monitored the coolant levels daily and kept the air con off. The journeys were maybe 4 miles each way per day, 2 miles on clear a roads 2 miles on motorway.

At that point the temp never exceeded 100, but in the last two weeks it started to climb so I decided to swap out the fan and we are now here. Have I damaged the engine by leaving the fan off?

I've personally never used K seal but I haven't clue if it has been used in the past.

Paul

***Update***

I've now driven to the shops and back, stop start most of the 3 miles, and as I was reversing into my drive the temp on the IPK hit 107 degrees.

I've once again checked the hoses and now the top hose is very hot whilst the bottom hose (with the bleed screw) is slightly cooler but still warm.

Still cannot understand why there is absolutely no drop in temp even after the fan kicks in especially as there must have been some air being forced through the rad as I was moving ( albeit at about 25-30 mph).

I've spent a good 15 minutes looking at the v from just about all angles possible and for the first time I've noticed a tiny bit of liquid just visible at the very back under the pipe from the thermos to the near side. It hard to find and small so i guess it evaporates quickly which is why I've never noticed it before especially when the engine has cooled.

Its quite possible that the thermos is original so it probably wise to change it if there is even a slight sign of a leak however could that slight leak be enough to cause the significant overheating?. Hopefully it can and maybe we've found the culprit at last.

What do you think Simon? Are my assumptions logical or is there anything else I can check.

Paul

T-Cut · 17th March 2021, 18:46

Hello Paul, there's clearly a coolant leak from the thermostat assembly which means air is getting into the cooling system. Without a regular bleed off, this will eventually form bubbles that get trapped in the convoluted system. The occasional gurgles suggest that's happening. From what you've reported here. I'd say it can all be down to insufficient coolant resulting in poor to little circulation through the radiator. This causes the counterintuitive temperature effects. Obviously, you'll be topping this up now and then. About how much and how often do you need it?

The V6 system does indeed pump coolant through the head bleed hose and into the header tank. I believe (thus far) it's the only engine of the three that does this. Observing the flow via the coolant filler neck will help eliminate water pump issues as suggested by Ducati750cc. The side entry on the header neck actually exits primarily from underneath the neck where it flows much faster from a larger vent hole. Here it is seen from inside the tank:

Hole 1 (which tends to get bunged up) operates a pressure diaphragm inside the cap's relief valve housing. The two o-rings seal it off when the cap's fitted.

Hole 2 is the primary air bleed into the header and is always operating.

LATE EDIT: Here's a photo showing you what to expect. You may have to rev the engine to get flows as fast as this:

The mayo under the oil filler cap isn't related to leakage from the thermostat, but an unconnected issue like a leak into the oil cooler will produce mayo where you've seen it. I think you're on track for a replacement thermostat, perhaps just new o-rings and maybe more.

TC

paulh260260 · 17th March 2021, 19:27

Quote:

Originally Posted by T-Cut

Hello Paul, there's clearly a coolant leak from the thermostat assembly which means air is getting into the cooling system. Without a regular bleed off, this will eventually form bubbles that get trapped in the convoluted system. The occasional gurgles suggest that's happening. From what you've reported here. I'd say it can all be down to insufficient coolant resulting in poor to little circulation through the radiator. This causes the counterintuitive temperature effects. Obviously, you'll be topping this up now and then. About how much and how often do you need it?

The V6 system does indeed pump coolant through the head bleed hose and into the header tank. I believe (thus far) it's the only engine of the three that does this. Observing the flow via the coolant filler neck will help eliminate water pump issues as suggested by Ducati750cc. The side entry on the header neck actually exits primarily from underneath the neck where it flows much faster from a larger vent hole. Here it is seen from inside the tank:

Hole 1 (which tends to get bunged up) operates a pressure diaphragm inside the cap's relief valve housing. The two o-rings seal it off when the cap's fitted.

Hole 2 is the primary air bleed into the header and is always operating.

LATE EDIT: Here's a photo showing you what to expect. You may have to rev the engine to get flows as fast as this:

The mayo under the oil filler cap isn't related to leakage from the thermostat, but an unconnected issue like a leak into the oil cooler will produce mayo where you've seen it. I think you're on track for a replacement thermostat, perhaps just new o-rings and maybe more.

TC

Cheers TC that great info, The cars at the garage diagnosing the trouble so I cant check the holes in the header tank. Hopefully the garages compression test will show no problem with the engine itself and as you say its just a thermos replacing needed.

If this is the case my thoughts to the next step are to flush the engine with wynns, replace the oil then take it on a good journey then check again.

Paul

15th March 2021, 23:14	#22
Ducati750cc Loves to post Rover75 tourer Join Date: Jun 2018 Location: Ashton Posts: 428 Thanks: 121 Thanked 206 Times in 145 Posts	The only thing that hasn't been mentioned and it is quite rare but not unknown on any engine, is that the impeller is loose on the water pump shaft, some cooling is attained when this happens but only by thermosyphoning, however when this does happen it is normally accompanied by a quite drastic temperature and pressure rise with the cap venting pressure and water, but this doesn't appear to be happening to yours. It's difficult to prove water movement/flow ( not pressure ) by the pump on many engines, nothing to see in most cases, but one way ( easier with vehicles with a separate remote expansion tank ) is to check, when cold and the cap is off, to see if water is flowing through the small de-gas pipe into the tank, just a dribble at idle and as the engine is revved the flow should increase and proves the pump is working. More difficult to see when the de-gas pipe enters the radiator top tank. My 75's are diesels, I'm presuming, but don't know, that your rad is the same as mine and the de-gas pipe fits onto a spigot just below the rad cap. If you remove the cap you should see a small hole just below the bottom seat of the cap in line with the spigot and water and possibly air should be seen issuing from this hole increasing as revs rise, if you disconnect the de-gas pipe you should be able to gently pass a piece of wire through the hole to ensure it's clear and able to do its job which is to remove any air bubbles in the system, if I get chance tomorrow I'll see if I can get some photo's of mine. I admit the above is a remote scenario but it's looking at clutching at straws time. A quick but pertinent question, have you done a correct cooling system pressure check which starts with a cold engine, the first test is the cap to see if it vents at the correct pressure and having vented retains pressure just below its lift pressure. Next is to pressurise the cooling system to just above the cap lift pressure, check for leaks and that there is no pressure drop over time. Next, pressure tester still fitted but previous test pressure released, engine started and pressure and temperature monitored ( increased idle speed sometimes needed ) until the fan comes on, at this point a healthy system will show pressure below the lift pressure of the cap and as the fan runs temp and pressure drops till the fan switches off. Sorry for the lengthy post, but there's a reason for your problem and sometimes throwing all the possibilities in the the pot and giving it a good shake find a solution. __________________ Common sense isn't a gift, it's a punishment because you have to deal with everyone who doesn't have it.

17th March 2021, 18:46	#24
T-Cut This is my second home Rover75 and Mreg Corsa. Join Date: Nov 2006 Location: Sumweer onat mote o'dust (Sagin) Posts: 21,752 Thanks: 341 Thanked 3,660 Times in 2,924 Posts	Hello Paul, there's clearly a coolant leak from the thermostat assembly which means air is getting into the cooling system. Without a regular bleed off, this will eventually form bubbles that get trapped in the convoluted system. The occasional gurgles suggest that's happening. From what you've reported here. I'd say it can all be down to insufficient coolant resulting in poor to little circulation through the radiator. This causes the counterintuitive temperature effects. Obviously, you'll be topping this up now and then. About how much and how often do you need it? The V6 system does indeed pump coolant through the head bleed hose and into the header tank. I believe (thus far) it's the only engine of the three that does this. Observing the flow via the coolant filler neck will help eliminate water pump issues as suggested by Ducati750cc. The side entry on the header neck actually exits primarily from underneath the neck where it flows much faster from a larger vent hole. Here it is seen from inside the tank: Hole 1 (which tends to get bunged up) operates a pressure diaphragm inside the cap's relief valve housing. The two o-rings seal it off when the cap's fitted. Hole 2 is the primary air bleed into the header and is always operating. LATE EDIT: Here's a photo showing you what to expect. You may have to rev the engine to get flows as fast as this: The mayo under the oil filler cap isn't related to leakage from the thermostat, but an unconnected issue like a leak into the oil cooler will produce mayo where you've seen it. I think you're on track for a replacement thermostat, perhaps just new o-rings and maybe more. TC Last edited by T-Cut; 17th March 2021 at 19:06..