Outer Limits 4x4 Board

I've been having some difficulty with my 3.9 V8 Disco.
Recently I changed the water pump as the old one crapped itself.
Ever since doing so she's been running warm, the gauge sits a little higher than it used to when driving, not much, not even over the 1/2 way mark. The problem is that when I stop she pressurises and blows coolant out the expansion tank cap.
There appears to be no bleader on the system besides the top of the radiator, I've filled the system as per the manual.
The engine's a serpentine belt model, yes the belt and viscious fan are on the correct way. I've just put the thermostat back in (didn't have one for about 18 months )
She runs really well except this problem.
I haven't had a timing light on her for about 2 1/2 years, though aside from that she's been serviced regularly including new plugs regularly.
I'm going to get the timing checked on Friday as I'm aware that incorrect timing can cause the problem.
The only other thing that I can think of is that I didn't drain the block drains when I emptied the system, could I still have an air lock in the system somewhere? Even though I've filled it by the book.

Please don't tell me I've got to do the head gaskets, speaking of which, I've compression tesed the engine and all cylinders are at 150psi.

I'm assuming by your name that your disco is a '95 model, which means it probably doesn't have the other bleeder above the right hand rocker cover (big metal pipe sticking up from a heater hose pipe)....

As for bleeding it, unscrew the top radiator plug fully, and take the expansion cap off. Run it till warm (thermostat open), and go around squeezing the hoses while its warm (you may need to stick the radiator plug back in one or two threads, so that only air can get out)

Its possible your expansion cap is stuffed.... The thing that interests me is that you've just put the thermostat back in - was this before or after if started playing up?

The thermostat could very likely cause your warmer running (due to it probably closing at your previous operating temp, then reopening when you get to that slightly higher temp you've been observing), but I don't see it making the car chuck coolant out - unless maybe it closes when you stop, and the pressure builds up behind it, but I would have thought the bypass through the thermostat would prevent that.

I highly doubt incorrect timing would cause it to chuck coolant out - it would have to be a fair way out, and you'd probably see a lot higher running temp first.

I'd probably have a good look at the expansion cap, see how it looks, and probably replace it, then see what happens. If it still chucks coolant, many workshops will test for blown head gaskets quite cheaply...

She was playing up before I put the thermostat in. I took it out on the side of the road one day when I had some other unrelated problems, and was just too lazy to put it back in. That was 18 months ago, she ran fine till I changed the water pump. So I put the thermostat in after the problem started.
As for the cap, that was my thought, so I put some ATV sealant on it, she definately sealed properly as once she got hot it blew the cap right off. It's supposed to be rated to 15 psi, if it holds too much pressure will it cause my problems?
I'll go downstairs and look for the bleeder you mentioned but I don't think it's got one.

Hmmm common causes of overheating.
How old is the radiator. The cooling system can build up with crud over time causing a partial internal blocking. Apparantly about 10 years is the life span.
Coolant - I assume your using it and not water.
Radiator cap - appropriate cap and sealing correctly?
Thermostat - Is this opening at the correct temp? You can get hotter 7 colder thermostats.
Viscous fan - are you sure this is working properly. (I recently replaced mine which fixed similiar problems to what you are describing).
Does it lose fluid and so potentially have head/head gasket problems?

TRobbo wrote:Hmmm common causes of overheating.
How old is the radiator. The cooling system can build up with crud over time causing a partial internal blocking. Apparantly about 10 years is the life span.
Coolant - I assume your using it and not water.
Radiator cap - appropriate cap and sealing correctly?
Thermostat - Is this opening at the correct temp? You can get hotter 7 colder thermostats.
Viscous fan - are you sure this is working properly. (I recently replaced mine which fixed similiar problems to what you are describing).
Does it lose fluid and so potentially have head/head gasket problems?

I've pretty much investigated all the avenues that you mention, possiblely the fan's not cutting in at correct temp, but I have a problem no matter what speeds I've been running at, and the problem actually seems a bit worse when I've been doing greater speeds.
Blocked rad, I put a flushing agent through the system already, which made absolutely no difference.

Tomorrow I'm getting a head test done to see if there's a problem there.
I don't know if I'm losing fluid as soon as I stop it pressurises and comes out the expansion cap.
No water in the oil, no oil in the water.

Flushing agents dont always work.

The horzontal cores hold dirt ect and harden there, blocking the cores and reducing cooling ability.

once you have checked fan for proper operation remove rad and have it rodded. IE: rem,ove tanks and clean/recore as required.

Fit latest natrad core.

Michael.

Its leaning towards head gaskets, i replaced mine without removing the inlet manifold by doing one at a time and just loosening the inlet man bolts. How many k's has it done ? rovers will rarely leak water to oil and vice versa.

210 000km. I know the inlet manifold needs doing too, maybe I'll do them both. I intend to trade her this year so I don't think I'll bother.
The mechanic I spoke to today (did his apprenticeship on D1's) reckons that mine sounds typical Disco head gasket.

I went down to the mechanics yesterday, head gasket test came back O.K. the mystery deepened, the mechanic rang the local radiator guy, who suggested "head gasket" till he was told everything that had been done.
Suggested that I needed to take a decent drive with the heater on, I may not have gone far enough, so I roasted all the way home 1/2 an hour or so.
Still no joy.
Finally found someone who had a new cap for the expansion tank ( or at least knew what he was talking about as it was the same one Autobarn and supercheap had) and changed that.
Drove home and finally found that my problem was solved
A $15 bloody cap , so all up it took me two weeks, cost 1/2 a dozen beers for the head check, about $30 worth of coolant, $5 for a flushing agent, and $15 for a new cap.
Beats the crap out of doing a head gasket

So are you saying one can buy a replacement cap at Autobarn???

If so, I wanna go get one - our Disco has a funny game called "hide the coolant". At seemingly random intervals when I check the coolant level before starting the car it has been as much as 15mm below the marker. However, topping it up solves the problem until some seemingly random amount of time it appears over filled. Sometimes the only reason I can see it has been overfilled is that it spills out of the cap vents.

You most certainly can. Don't let the children there tell you it doesn't fit.
The brand is C.P.C. model No 572 135. Pretty sure it's listed as the cap for the V6 Commodore, I can tell you right now, that's what's on my 3.9 V8 expansion tank.

Ripper!

Just to be sure I will take the one off the Girlie's VS and try it!

Thanks for the lead.

Digging up an old thread here....

I have just had a look on the CPC site, who recommend a 16 PSI cap for all the Rangie V8's.

The one thing I am confused about is what the difference between a recovery system cap and standard cap is. I imagine I should use a standard cap for the Rangie as there is no reservoir, but I am unsure what the difference is, being that I would think they would both release pressure when it reaches 16PSI.

At the moment I have a 15PSI Recovery System CPC cap on, which allows coolant to leak when I come to a stop similiar to the OP.

Also, is 16 PSI too high for a RR3.9?

Thanks,

Luke

Hi Luke,

Don't know what year your RR is. I have an older classic (74/81) with the brass pressurised expansion tank. Had similar issues. Turned out to be a combination of an air lock in the block / hoses and a faulty cap. The cap on the exp tank has a little valve in the middle that lets air back into the top as the coolant cools and contracts. Mine was sticking and sucking air instead from a joint on the lpg converter, as it cooled down.

Result was even more air in block / rad which expanded more again when heated, forcing even more coolant out when hot, and so on. Changed cap and bled all air out by putting RR on big angle so filler on rad was highest point, running to temp and squeezing hoses. All is now well.

I'm not sure which cap is called what but my stock system needs the one with the little air return valve in the middle.

Mine has a 350 Chev, std 3.5 rad and exp tank and twin thermos and never goes over half on the temp gauge ; but I do wonder at times if the std exp tank is big enough for a Chev........ anyone have thoughts?

cheers, DL

When I had a chev powered rangie, I had a tube from the expansion tank leading to a 1.25ltr coke bottle sitting next to the radiator (below battery height). Not sure how much good it did, but it didn't do any harm and didn't cost anything either.

yeah early model Commodores and some Discos use the same expansion tanks made by...Mercedes...it's a wierd world!

TRobbo wrote:When I had a chev powered rangie, I had a tube from the expansion tank leading to a 1.25ltr coke bottle sitting next to the radiator (below battery height). Not sure how much good it did, but it didn't do any harm and didn't cost anything either.

Sounds like a good idea. At least that way I shouldn't loose my coolant.

I'll have to check out both types of caps, recovery and standard, and see if the valve to allow air to suck back in is the difference. If so that could be my problem

LukeV

Thanks TRobbo,

Did you fill the exp tank right up when using the coke bottle? No air involved that way. Reason I ask is if I just cover the plate at the bottom of the exp tank I will have to top it up a little bit over time to the same level, which is why I asked the question about Chevs. I'm thinking that you had a set up like XD to XF Falcons that just suck fluid back into the pressurised system, rather than trying to maintain an air/coolant thing in the exp tank.

cheers, DL

My Disco's still running over temp Wouldn't say she's hot, just too warm....Radiator man put an exhaust gas sensor in the expansion tank, sounded like a goddamnec air raid siren
Looks like I'll be doing head gaskets very soon.