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Discussion Starter #1
Going on hour 3 on RR.net tonight... My 96 RR 4.6 overheats and its getting worse.

It has done it a handful of times over the last year, but the frequency is increasing, and now its once a week.

Here is what happens:
The gauge goes up, it happens fast and usually under slow speed conditions. I pull over. Sometimes i can hear my heater o-rings seeping air which means the coolant is low. I get out. Observe coolant leaking under the car from somewhere behind the firewall. I release the expansion cap slowly, and release a lot of air. Top off the coolant tank. Get back in the car, notice the temp gauge back to normal, and immediately drive off as if it never happened. Its fine for another few days/week.

Here the LR shop said:
Took it to a reliable indie tech. He says "sounds like head gasket." Does a couple hours of testing. Compression in each cylinder is good, oil looks good, says fan feels good, pump is functioning. He was able to get it to overheat after some time, and put a coolant sniffer on it, which indicated exhaust in the coolant. He says "bad head gasket." Cost: $1500 for gasket only, $1800 for gasket and valve job while they're in there.

Here's what i'm thinking:
Ok, maybe the head gasket is not that great, but its not that bad. But when its overheating, something expands or contracts, and yeah it pushes out a little exhaust into the coolant. But what if thats not the cuase of the overheating, just a symptom?

Here's some info about the car:
My coolant hoses are always supple.The top hose can get pretty hot when overheating. The bottom hose of the rad is always cold. Heater always works great except when coolant is really low just after overheating. Car runs smooth, plenty of power. No steamy exhaust as far as i can see. It has a relatively new radiator that i put in over the summer, because the old one had a leak. The heater o-rings leak a little but i haven't bothered to fix. (because the car could explode tomorrow and i'd rather not ruin new o rings.)

Q's:
1. Is a certain amount of pressure in the cooling system necessary for proper functioning? i.e. can you drive without a cap on the expansion tank theoretically? My heater o-rings leak a little, and i can hear air cumming out of them inside the cabin when the coolant is low. Perhaps i don't have enough pressure due to the bad o-rings?
2. My temp gauge has been reading just past 12 o'clock for the last few months. Usually it indicates just shy of 12 o'clock. Would that indicate a bad thermostat? How long do thermostats last? How likely is one to go bad?
3. How low a level of coolant can you have in the expansion tank before you start to have flow/overheating issues?
4. If I had a perfectly sealed head gasket, and the car overheated, would you expect that gasket to fail under abnormally hot conditions?
5. If you have a bad head gasket, does coolant typically get drawn into the combustion chamber, as well as exhaust gasses getting pushed out of it?
6. What are the odds the head gasket would fail at the two small areas contacting the chamber which caries the coolant?
7. If i had a slipped liner (tech says won't know until the head is taken off), would i be experiencing this same coolant pressurization? And if so, is that more likely than a bad head gasket?
8. Is it possible that one of my exhaust valves is sticking, putting excess pressure in the combustion chamber, which pushes coolant out at the head gasket? This would explain the one-way direction of the leak/pressurization. And if so would this cause the car to run poorly?
9. Where do babies come from?

Please Help!
 

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Re: Attention Sherlock Holmes/smart people. Overheating issues.

headgasket, seen it before.

1. Is a certain amount of pressure in the cooling system necessary for proper functioning? i.e. can you drive without a cap on the expansion tank theoretically? My heater o-rings leak a little, and i can hear air cumming out of them inside the cabin when the coolant is low. Perhaps i don't have enough pressure due to the bad o-rings?
The pressure raises the boiling point of water, the glycol helps, but coolant will boil with no cap, even sitting at idle for too long. bad orings isn't helping. bypass your heater core till you can get them fixed (may be mimicing a failed HG and will do the trick.)


2. My temp gauge has been reading just past 12 o'clock for the last few months. Usually it indicates just shy of 12 o'clock. Would that indicate a bad thermostat? How long do thermostats last? How likely is one to go bad?
possibly bad, they're cheap(ish), replace it, they are made by LR afterall.


3. How low a level of coolant can you have in the expansion tank before you start to have flow/overheating issues?
as long as there's water in the line you'll have flow, but I wouldn't push it...


4. If I had a perfectly sealed head gasket, and the car overheated, would you expect that gasket to fail under abnormally hot conditions?
If you bake your engine lots of stuff will fail, stoping quickly you may have saved it.


5. If you have a bad head gasket, does coolant typically get drawn into the combustion chamber, as well as exhaust gasses getting pushed out of it?
both, on the intake stroke the cylinder is at a vacuum, allowing coolant in, on the up-stroke there is pressure, pushing exhaust out.

6. What are the odds the head gasket would fail at the two small areas contacting the chamber which caries the coolant?
good enough to bet a paycheck on, that's the most common spot in most engines.


7. If i had a slipped liner (tech says won't know until the head is taken off), would i be experiencing this same coolant pressurization? And if so, is that more likely than a bad head gasket?
possibly, and equally likely to be either

8. Is it possible that one of my exhaust valves is sticking, putting excess pressure in the combustion chamber, which pushes coolant out at the head gasket? This would explain the one-way direction of the leak/pressurization. And if so would this cause the car to run poorly?
no, well, it's possible you have a sticky exhaust valve, but that would produce LOW pressures in the cylinder, not high. combustion is where you get the high pressures, if the exh valve leaks you won't have enough compression to even combust (if it's bad..), yes it would cause poor running.

9. Where do babies come from?
if you havn't figured it out by now....
 

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Discussion Starter #3
Re: Attention Sherlock Holmes/smart people. Overheating issues.

Thanks for the response! A few more q's:

2B. How long do thermostats typically last? (mine is at least 5 years)
4B. If you had a brand new p38 and you ran it low on coolant, would you expect the head gasket to start seeping once its began to overheat?
5B. If a bad head gasket would allow both exhaust out of the chamber into the cooling system, and coolant into the chamber on the draw, then wouldn't i see steam coming out of my exhaust?
10. If coolant is flowing properly, would you expect the bottom hose off of the radiator to be at least warm to the touch?
11. Typically how resilient are p38 engines to being overheated? Example, A p38 just barely goes into the red a handful of times, but not enough to trigger the red light, would you expect engine damage is likely, somewhat likely, or not likely?
 

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Re: Attention Sherlock Holmes/smart people. Overheating issues.

pdxRR

It's funny how we always suspect the worst and ignore the simplest.

Your problem sounds very similar to the one I had when I bought my RR some years ago.

You say you can hear the heater o-rings seeping air. Are you sure this is what you are hearing?
Maybe it is your resevoir cap venting.

The boiling point of your coolant is determined by the pressure. The higher the pressure the higher the boiling point.
The pressure is regulated by the cap. It vents at 1.4 bar.
If the cap is faulty, it will vent early and the coolant pressure will be low.
Because of the lower pressure your coolant will be able to boil.
When it boils it vents out of the relief tube and ends up on the ground.
No leak can be found because there is none. The cap is doing it's job, but just not correctly.
There's really no way to test the bloody thing, you can only replace it and see how you go.

I cured my problems permanently by just replacing the cap, for around $20.
Maybe you can do the same?

It's worth a try, is it not, before you spend the big bucks chasing other more expensive issues.

Cheers
 

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Re: Attention Sherlock Holmes/smart people. Overheating issues.

Had a bit more of a think about your problem.
That's not to say you don't try the coolant cap fix first.

Quote: "My coolant hoses are always supple"

This indicates to me that the system is not getting pressurized.
Under full pressure the top hose should be very firm.
If it's not then you are venting pressure somewhere.
The first guess is the cap.

If this doesn't fix it, you must have a leak somewhere, and if it can be good for up to a week after topping up, the leak must be very small.

Another Rangie I owned had such a leak, I couldn't find it for love or money, until one day, when I had the bonnet up in full sunlight I saw a faint wisp of steam emerge from one of the heater hose clamps. On that day I was pressed for time so I didn't have a chance to replace the clamp.
I put in some Wynn's radiator "stop leak" as an interim measure which fixed the problem.

The thing is I never did have to come back to it, and ended up selling the car a couple of years later with the fix still good.
That stuff really worked!

The take home point being, you have a small leak somewhere.
It can be hard to find but keep looking
You may not have find if you are feeling beat, if you put in the right stuff.
After all, it's standard prectice now for many manufacturers to put in a "stop leak" as part of the delivery fluids from what I've being told.

Cheers again.
 

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Re: Attention Sherlock Holmes/smart people. Overheating issues.

If coolant sniffer detected fumes in coolant then gasket is blown.

A few things to consider when the work is being done.
1 remove, flush and clean radiator, while thats all out clean ac condenser reverse of air flow, believe me they block up badly
2 inspect water pump (remove) and test fan viscous coupling
3 reservoir cap to be tested, maybe its not holding pressure

lets hope you dont have the liner issue.......
 

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Re: Attention Sherlock Holmes/smart people. Overheating issues.

To answer your question about how the engine holds up to overheating. It is HYPER sensitive to heat. NEVER overheat it. The sleeves will slip and you will need a new engine. Sometimes if it was overheated, the engine can run with a partially slipped sleeve for a year or so, often times you can hear the liner making a deep tapping noise.
 

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Discussion Starter #8
Re: Attention Sherlock Holmes/smart people. Overheating issues.

Thanks all for your advice and support. I bought a new cap today and i plan on bypassing my heater core to eliminate that as a source of pressure loss/leak. (hopefully nothing blows out) I will post my findings.

Has anyone had a faulty cap? What were your symptoms?
Also has anyone had a bad head gasket and noticed steam out of the exhaust?
 

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Re: Attention Sherlock Holmes/smart people. Overheating issues.

Hi pdxRR,

As I said in my earlier post, I have had a faulty cap and the symptoms were very similar to yours.
Don't stress out over stem coming out of the exhaust.
Steam will always come out of the exhaust, even with a perfect head gasket, as water is one of the combustion products.
CO2, H2O and other pollutants in small %ages.

What you don't want to have is coolant coming out of the exhaust, as that would indicate a faulty gasket.

The coolant is easy to pick up.
Idle the motor and put your hand close to the exhaust, and it will quickly become moist.
When you move it away, your hand should dry out and not remain sticky.

If it stays sticky, that's coolant, and you can also smell it quite distinctly.

Simple but effective check
 

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Re: Attention Sherlock Holmes/smart people. Overheating issues.

I suspected a head gasket problem and used a product called Blue Devil, a silicate product to temporarily repair head gasket leaks, directions say pour in rad and drive car, much simpler than other brand silicate sealers. This solved my overheating problem for a year,inevitably I had to do the head gasket job, but this told me what my problem was and gave me some time to prepare for job. The drawback is the cost of blue devil is $60 , and I had to order it online.
 

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Re: Attention Sherlock Holmes/smart people. Overheating issues.

pdxRR said:
Thanks all for your advice and support. I bought a new cap today and i plan on bypassing my heater core to eliminate that as a source of pressure loss/leak. (hopefully nothing blows out) I will post my findings.

Has anyone had a faulty cap? What were your symptoms?
Also has anyone had a bad head gasket and noticed steam out of the exhaust?
I replaced my collant cap a couple of weeks ago as i was losing coolant on short runs. Since i purchased the vehicle 2 yrs ago my coolant level was always happy to stay at about 1cm below the level arrow. Recently i noticed it dropping below this level and had to frequently top it up. After a trip of 40miles i checked the level and was shocked to see it had dropped to almost the bottom of the coolant tank. Since replacing the new colant cap my water level has maintained a constant level right at the correct point indicated by the level arrow. My advice to anyone who has a coolant level below the correct level is to change your cap as soon as you can before the cap wears out any further and causes more expensive problems.
I too checked my top hoses durng the loss of coolant period and they were always soft, so i suspect the advice given in other replies above that a bad cap allows venting of the system at a lower pressure is right .
Good luck and keep us updated on your problem.
Nigel
 

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Re: Attention Sherlock Holmes/smart people. Overheating issues.

Well pdxRR.

How did you go?
 

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Discussion Starter #13
Re: Attention Sherlock Holmes/smart people. Overheating issues.

A week ago, i took the thermostat out and forced it open with some copper wire and re-installed it, pending arrival of a replacement. I've been driving it around on short trips for week now in 20-30 degree weather and the engine barely warms up. Not exactly a conclusive test, due to the fact that its freezing outside, but i suspect it was likely that i had a bad thermostat. I didn't need to bypass the heater core, as my o-rings have since stopped leaking, probably because the coolant is not getting hot enough to pressurize the system.

I will be installing a new thermo this weekend and see what happens. fingers crossed.
 

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Re: Attention Sherlock Holmes/smart people. Overheating issues.

Definately sounds like a sticking thermostat. Whats happening is your cooling system is pressuring up to the point where it overpowers your o-rings and releases said pressure. The reason your engine is not running hot with the thermostat removed is the coolant is not stopping in your block to heat up and waiting for your thermostat to open and circulate it to the rad. In other words, it's always on the move and doesn't get the chance to heat up to operating temp. I would get that fixed asap and drive the truck as little as possible till you get it replaced. Aluminum block + steel cylinder sleeve = differant coefficients of expansion. I would bet the engine designers allowed for this so that when the engine is at normal operating temp everything seals just right, that should put an end to your leak and overpressure problem. Good luck. Just looked outside at the thermometer outside kitchen window, -27 C, Burrrrr.
 

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Re: Attention Sherlock Holmes/smart people. Overheating issues.

I have a dollar payable via paypal that says replacing the thermostat won't change a thing.
 

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Re: Attention Sherlock Holmes/smart people. Overheating issues.

Care to make it $100?
 

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Re: Attention Sherlock Holmes/smart people. Overheating issues.

Coefficient of aluminum=248 , coefficient of steel=121. You be the judge. Got any advice mag?, or just rheteric. :(
 

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Re: Attention Sherlock Holmes/smart people. Overheating issues.

Last saturday i put in a new thermostat, its the end of wednesday and so far its like the whole ordeal never occured. No more overheating and incredibly the heater core o-rings have stopped leaking as well No problem idling in traffic, no more temp gauge creeping up, no more turning the heat on full blast with the windows down.

Perhaps i'm counting eggs before they've hatched but the temperature here has been in the 40's, which is warmer than it was when i was experiencing the problems. I suppose the true test will be in August.

If anyone needs to buy a new thermostat, desertboy was kind enough to point me towards a cheap source (only $26):

http://sd.autohausaz.com/autohausaz/det ... Thermostat

I would recommend to anyone with an overheating rover to replace the thermostat and the expansion tank cap first. Just because its the cheapest.
 
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