2.5V6 coolant and fan woes - Page 6

SD1too · 2nd October 2016, 09:30

A small imperfection in an exhaust manifold to catalytic converter gasket will readily leak exhaust gases at idle, particularly when the engine is cold. I have one at the moment on our other car. Why do you think that a head gasket would behave differently?

Also, I notice that you speak of gas volume. Why volume and not pressure? Are you saying that there's insufficient pressure at idle to eject exhaust gases through a head gasket defect?

Sorry, I'm not yet convinced.

Simon

T-Cut · 2nd October 2016, 18:22

Quote:

Originally Posted by SD1too

Sorry, I'm not yet convinced.

Let's hope Forestgreen comes back for the finale.

TC

SD1too · 2nd October 2016, 18:40

That's cheating. If you have confidence in your theory then surely you can justify it.

Simon

Phil-T4 · 2nd October 2016, 18:43

Head lift could be another cause.

T-Cut · 2nd October 2016, 21:20

Quote:

Originally Posted by Phil-T4

Head lift

You mean explosive lift? - slack or over-elastic bolts??

TC

Phil-T4 · 2nd October 2016, 21:26

Quote:

Originally Posted by T-Cut

You mean explosive lift? - slack or over-elastic bolts??

TC

Yes - just throwing another possible cause into the equation

TomRS · 3rd October 2016, 13:27

The OP stated that his car hit the "red light" overheating that means its more than likely got to the stage of being too hot.

What could have started out as a air lock has now manifested into HGF due to the extreme overheating that has happened.
the gauge doesnt move upto 112 from middle so at what temperature does the "red light" come on?
Must be 130+ which is too late especially if happened more than once!

SD1too · 3rd October 2016, 15:39

Quote:

Originally Posted by TomRS

... has now manifested into HGF due to the extreme overheating that has happened.

There is no evidence of head gasket failure Tom, and the red coolant LED illuminated just once I believe, and the owner took immediate action to replace lost coolant. I don't call that "extreme overheating".

MGR doesn't give an exact temperature for red LED illumination, but it does say that it extinguishes when the temperature drops 3° below "the maximum" shown on the gauge. With such a vague explanation you cannot assume that the coolant is over 130°C.

Simon

SD1too · 3rd October 2016, 18:54

David,

I think that we have reached the stage where a review of all the evidence and advice would be beneficial, so that's what I've done.

The primary problem is clearly coolant loss.
Your engine isn't overheating, at least in any sustained way.
There is no evidence of head gasket failure.

So, why are you losing coolant repeatedly?

The most obvious reason is a leak, which would also prevent proper pressurisation which could explain the odd temperature variations (e.g. a momentary rise to 108° when accelerating under load up a hill after a motorway run). Observation is your best weapon here. Remove the engine undertray and have a good look from underneath with the engine running. Be certain that no coolant is escaping through the expansion tank cap.

The other odd thing is the radiator fan. I'd recommend a thorough inspection of the control box circuit, the connectors to the car's main loom, the resistor, and the number of cables entering the motor housing. The evidence suggests that some undetected bodgery has taken place here.

I'm sure that Steve (Arctic) and his team will be only too pleased to assist you at one of their meetings.

Simon

Forestgreen · 3rd October 2016, 19:36

Thanks Simon.

Someone asked about prolonged overheating. Four times in the five years that I've owned the car the temperatuire gauge has shot up and the red "engine overheating" instrument panel warning has come on. Each time I've immediately pulled over and let the engine cool down before adding coolant. Is it normal for a car to overheat this often or have I been unlucky, and has the overheating been sufficient to goose the engine? I do check the coolant levels monthly, but it seems unreasonable to have to check them before practically every journey, which is what I'm now having to do. Diary of overheating light:

(i) just after buying the car - caused by leaky thermostat. If this was the reason for the previous owner selling up, there's no knowing how often it overheated prior to this.
(ii) four years later (last year) - replacement thermostat leaking, replaced again.
(iii) this summer - traced to the water pump which I duly replaced along with the belts which were due at the end of 2016 in any case.
(iv) a few weeks later - and still undiagnosed yet leaking 500 mls of coolant every 100 miles.

Pressure testing the system failed to elicit any leak external to the engine. No evidence of any air pockets either. However, testing the coolant demonstrated that combustion gases were getting into the cooling system. This correlates with the observation that after a run from cold, with the coolant cap off beforehand to equalise pressure, there is a release of gas when I next check the coolant level on a completely cold engine. I am interested to know what else besides a cracked head or a gasket failure can do that?

As I'm not a mechanic and I depend on having a reliable car for my work, I simply cannot afford to spend any more time taking Forestgreen in and out of garages trying to find a considerable but untracable coolant leak. The next step is going to have to be either

(i) a new engine,
(ii) a full send away strip down and rebuild of the existing engine, or
(iii) a new car.

Being in very good condition cosmetically and on only 70,000 miles, if I did sell the car I would want it to go to a mechanically minded enthusiast who like me will cherish it but be not so dependent on its reliability or who is willing to take it to pieces whenever something goes wrong. I appreciate that a new engine comes with risks and a rebuild won't happen without money, but would still be cheaper than another car. Just a pity that I only just fitted new cambelts and water pump and that's probably £500 down the drain.

2nd October 2016, 09:30	#51
SD1too Doesn't do things by halves Rover 75 2.5 Connoisseur Auto (1999) Dealer launch model. Join Date: Mar 2007 Location: Former Middlesex Posts: 20,420 Thanks: 1,587 Thanked 3,749 Times in 3,181 Posts	A small imperfection in an exhaust manifold to catalytic converter gasket will readily leak exhaust gases at idle, particularly when the engine is cold. I have one at the moment on our other car. Why do you think that a head gasket would behave differently? Also, I notice that you speak of gas volume. Why volume and not pressure? Are you saying that there's insufficient pressure at idle to eject exhaust gases through a head gasket defect? Sorry, I'm not yet convinced. Simon __________________ "Whatever is rightly done, however humble, is noble." Sir Henry Royce.

2nd October 2016, 18:40	#53
SD1too Doesn't do things by halves Rover 75 2.5 Connoisseur Auto (1999) Dealer launch model. Join Date: Mar 2007 Location: Former Middlesex Posts: 20,420 Thanks: 1,587 Thanked 3,749 Times in 3,181 Posts	That's cheating. If you have confidence in your theory then surely you can justify it. Simon __________________ "Whatever is rightly done, however humble, is noble." Sir Henry Royce. Last edited by SD1too; 2nd October 2016 at 18:52.. Reason: Improved semantics

3rd October 2016, 13:27	#57
TomRS Posted a thing or two Mk1 ZT 190 - Mk2 ZS 180 - Mercedes E63 AMG S - Ford Ranger Hawk Join Date: Mar 2016 Location: Middlesbrough Posts: 1,456 Thanks: 123 Thanked 409 Times in 281 Posts	The OP stated that his car hit the "red light" overheating that means its more than likely got to the stage of being too hot. What could have started out as a air lock has now manifested into HGF due to the extreme overheating that has happened. the gauge doesnt move upto 112 from middle so at what temperature does the "red light" come on? Must be 130+ which is too late especially if happened more than once! __________________ http://i66.tinypic.com/5cd6xj.jpg

3rd October 2016, 18:54	#59
SD1too Doesn't do things by halves Rover 75 2.5 Connoisseur Auto (1999) Dealer launch model. Join Date: Mar 2007 Location: Former Middlesex Posts: 20,420 Thanks: 1,587 Thanked 3,749 Times in 3,181 Posts	A review David, I think that we have reached the stage where a review of all the evidence and advice would be beneficial, so that's what I've done. The primary problem is clearly coolant loss. Your engine isn't overheating, at least in any sustained way. There is no evidence of head gasket failure. So, why are you losing coolant repeatedly? The most obvious reason is a leak, which would also prevent proper pressurisation which could explain the odd temperature variations (e.g. a momentary rise to 108° when accelerating under load up a hill after a motorway run). Observation is your best weapon here. Remove the engine undertray and have a good look from underneath with the engine running. Be certain that no coolant is escaping through the expansion tank cap. The other odd thing is the radiator fan. I'd recommend a thorough inspection of the control box circuit, the connectors to the car's main loom, the resistor, and the number of cables entering the motor housing. The evidence suggests that some undetected bodgery has taken place here. I'm sure that Steve (Arctic) and his team will be only too pleased to assist you at one of their meetings. Simon __________________ "Whatever is rightly done, however humble, is noble." Sir Henry Royce.

2nd October 2016, 18:43	#54
Phil-T4 I really should get out more....... MG ZT-T, Rover 75 Tourer Join Date: Mar 2011 Location: Olney Posts: 2,969 Thanks: 245 Thanked 1,088 Times in 657 Posts	Head lift could be another cause.

3rd October 2016, 19:36	#60
Forestgreen Gets stuck in Rover 75 Connoisseur SE 2.5 V6 saloon Join Date: Dec 2011 Location: Birmingham Posts: 770 Thanks: 47 Thanked 105 Times in 54 Posts	Thanks Simon. Someone asked about prolonged overheating. Four times in the five years that I've owned the car the temperatuire gauge has shot up and the red "engine overheating" instrument panel warning has come on. Each time I've immediately pulled over and let the engine cool down before adding coolant. Is it normal for a car to overheat this often or have I been unlucky, and has the overheating been sufficient to goose the engine? I do check the coolant levels monthly, but it seems unreasonable to have to check them before practically every journey, which is what I'm now having to do. Diary of overheating light: (i) just after buying the car - caused by leaky thermostat. If this was the reason for the previous owner selling up, there's no knowing how often it overheated prior to this. (ii) four years later (last year) - replacement thermostat leaking, replaced again. (iii) this summer - traced to the water pump which I duly replaced along with the belts which were due at the end of 2016 in any case. (iv) a few weeks later - and still undiagnosed yet leaking 500 mls of coolant every 100 miles. Pressure testing the system failed to elicit any leak external to the engine. No evidence of any air pockets either. However, testing the coolant demonstrated that combustion gases were getting into the cooling system. This correlates with the observation that after a run from cold, with the coolant cap off beforehand to equalise pressure, there is a release of gas when I next check the coolant level on a completely cold engine. I am interested to know what else besides a cracked head or a gasket failure can do that? As I'm not a mechanic and I depend on having a reliable car for my work, I simply cannot afford to spend any more time taking Forestgreen in and out of garages trying to find a considerable but untracable coolant leak. The next step is going to have to be either (i) a new engine, (ii) a full send away strip down and rebuild of the existing engine, or (iii) a new car. Being in very good condition cosmetically and on only 70,000 miles, if I did sell the car I would want it to go to a mechanically minded enthusiast who like me will cherish it but be not so dependent on its reliability or who is willing to take it to pieces whenever something goes wrong. I appreciate that a new engine comes with risks and a rebuild won't happen without money, but would still be cheaper than another car. Just a pity that I only just fitted new cambelts and water pump and that's probably £500 down the drain.