Thread: 3.9 V8 ran hot yesterday....what now?

Originally Posted by LRJim

Yes but I'm wondering if it's just bubbling out of the expansion cap? That's the only evidence I've found.

Yep. Same story with the Camry.
It could be that the head gasket is blown between the cylinder and a water jacket. This would cause these symptoms.
If you had the coolant analysed, I suspect it would have exhaust gasses in it.
It sounds like it is in the early stages. Time to take stock as to what you have got. Do a cooling system pressure test and compression test. That will tell you more or tell you to look elsewhere.

I know of another 3.9 that is overheating for inexplicable reasons. AFAIK, the compression test and cooling system pressure test tested ok.

I have had the same issues in the past, if the temp gauge moves its to hot, once they start to go up there is a issue, if all is good they never move from normal regardless of conditions.
First things first, if you have done any bog holes or muddy tracks very carefully check the radiator for mud in the fines, I now avoid mud like the plaque but used to play pretty hard... always cleaned the mud out but the fan side of the radiator was chockers and caused overheating as soon as it was hot weather or the car worked hard. The only real way to check this is remove the fan shroud and fan or the radiator.
Given it is fine at 80-100 and cruising it would be that or the fan is not locking up, if the fan is working properly when started from cold it will be fully locked for a short moment and you will hear it roar, same when its hot, you can hear the fan fully locked up and it sounds like a jet engine. If working properly they suck more air and work better than electric fans.
If the radiator and fan are both in working order check thermostat and water pump are good

Originally Posted by discomatt69

I have had the same issues in the past, if the temp gauge moves its to hot, once they start to go up there is a issue, if all is good they never move from normal regardless of conditions.
First things first, if you have done any bog holes or muddy tracks very carefully check the radiator for mud in the fines, I now avoid mud like the plaque but used to play pretty hard... always cleaned the mud out but the fan side of the radiator was chockers and caused overheating as soon as it was hot weather or the car worked hard. The only real way to check this is remove the fan shroud and fan or the radiator.
Given it is fine at 80-100 and cruising it would be that or the fan is not locking up, if the fan is working properly when started from cold it will be fully locked for a short moment and you will hear it roar, same when its hot, you can hear the fan fully locked up and it sounds like a jet engine. If working properly they suck more air and work better than electric fans.
If the radiator and fan are both in working order check thermostat and water pump are good

Well it was the 1st time it's ever moved, it had a big day towing a trailer earlier on in the day then the drive to my sister's. No time to cool then a hard up hill drive to the forest then even harder hitting the tracks.
I noticed a little bit of wetness on the drivers side of the firewall towards the back. Is there a Welsh plug near the trans dipstick? It could be splash up though.
I'm gonna pull the radiator out and clean it properly I'm always on dirt roads and have had the headlights under the mud a few times. I've rarely heard the fan engage I know exactly what it sounds like so maybe that's a problem. I think it was doing it's job but I can't hear **** from inside. Need to find out temp it engages and test off the sensor with a multi. My old rodeo had a viscous fan that was always engaged, kept it running a few thousand ks.
The disco still runs well so hopfully i caught it quick enough
Cheers

Reading RAVE it seems to have a drain plug where it looks like it's wet I think I'm gonna check that 1st.

I'd doubt it's a head gasket(for now), otherwise you'd have had issues before and after.

Going by your scenario, as the other's have said, viscous and rad.

Rad flush may not actually helps in some instances.
I have a story where I thought I flushed my Tdi's rad when all water came out clean, but after trying the CEM flush stuff, it came out murky again when used as they instruct too.
That is, I ran with straight water for a short time to keep an eye on water colour. It stayed clean, and when I had the time I looked for various options. Added the yellowy looking CEM rad flush ran for a day(they say less, but that's just how it ended up for me).
The now yellowy/green water came out brown murky crud when bottom rad hose was pulled.
Ran hose through system again and more brown murky water came out.

I don't have a V8 of your model(mine is a '00 D2), but viscous will be locked for a good minute or two from a stone cold startup, and you hear it well and good.
It then decouples so the airplane taking off sound disappears. then obviously as it reaches it's coupled temp again it locks itself up and your Disco sounds like a jet plane again!

I used to use a cold store riggers glove to hold the fan with the engine idling at operating temp. The padded glove stops getting fingers chopped off!.
Hold fan, get a helper to start engine when hot. You could try to stop it whilst the engine is idling, but there's always a chance that you could break fan blades or more importantly hurt self.

But if I were in your shoes(or car) I'd be totally sus on the viscous initially.

ps. get a temp gauge too. I suspect that if your temp gauge 'just moved' then coolant temp probably touched over 110°C.
There are probably a million and one ways to fit a coolant temp probe and I've so far tried two.
First try was a total shambles and I'm too embarrassed to describe it, but second try was using a brass plug with a tapped hole, not quite made for the job, where the NPT threaded VDO sender fitted into.
I recently contacted the MadMan local contact and purchased much better fitting brass bungs with made for the job NPT thread.

Originally Posted by AK83

I'd doubt it's a head gasket(for now), otherwise you'd have had issues before and after.

Going by your scenario, as the other's have said, viscous and rad.

Rad flush may not actually helps in some instances.
I have a story where I thought I flushed my Tdi's rad when all water came out clean, but after trying the CEM flush stuff, it came out murky again when used as they instruct too.
That is, I ran with straight water for a short time to keep an eye on water colour. It stayed clean, and when I had the time I looked for various options. Added the yellowy looking CEM rad flush ran for a day(they say less, but that's just how it ended up for me).
The now yellowy/green water came out brown murky crud when bottom rad hose was pulled.
Ran hose through system again and more brown murky water came out.

I don't have a V8 of your model(mine is a '00 D2), but viscous will be locked for a good minute or two from a stone cold startup, and you hear it well and good.
It then decouples so the airplane taking off sound disappears. then obviously as it reaches it's coupled temp again it locks itself up and your Disco sounds like a jet plane again!

I used to use a cold store riggers glove to hold the fan with the engine idling at operating temp. The padded glove stops getting fingers chopped off!.
Hold fan, get a helper to start engine when hot. You could try to stop it whilst the engine is idling, but there's always a chance that you could break fan blades or more importantly hurt self.

But if I were in your shoes(or car) I'd be totally sus on the viscous initially.

ps. get a temp gauge too. I suspect that if your temp gauge 'just moved' then coolant temp probably touched over 110°C.
There are probably a million and one ways to fit a coolant temp probe and I've so far tried two.
First try was a total shambles and I'm too embarrassed to describe it, but second try was using a brass plug with a tapped hole, not quite made for the job, where the NPT threaded VDO sender fitted into.
I recently contacted the MadMan local contact and purchased much better fitting brass bungs with made for the job NPT thread.

From memory the viscous come on at startup, im pretty sure it comes on in traffic. Can you pull them apart and refill refill the silicone in them or are they just a throw away part?
Well I've flushed it with a product and ran it for about 40 mins the bottle said 1hr max.
Ive flushed it 3 times with water now and it looks pretty clean, that bottom hose is a pain to get to. Just need to refill with coolant now.
I'll definitely be getting an aftermarket gauge of some description, I really wanna rig up my android and use rovergauge permanently.
But a small digital one like a turbo timer would be great.
Cheers Jim

Originally Posted by LRJim

.... Can you pull them apart and refill refill the silicone in them or are they just a throw away part?
.....

Not done it myself, but I think I've read that other's have done.

Sounds like it may be OK then. Can still fool 'ya tho.
My D1 kind'a did. I did the (rolled up)newspaper test this time around, where you wedge a paper between the blades, and then the paper through to something else.
The idea is to keep it rigid enough to stop it spinning, but as it gets hot, it then knocks the paper out of the other end and/or cuts through or bends it at the fan end.
Mine didn't budge, and I could freely turn the fan the opposite way even tho I had the engine up to 85°C at the time.

Years back on my RRC, I had the unfortunate experience to have my rad rot itself to dust!
Run fingers mediumly(if that's a word! ) across fins, mainly middle-bottom to feel how solid they are.

And one other thing I found earlier this year: I posted about it before in other threads.

Noting that I have a digital temp gauge, and is about as accurate as I think necessary(tested against IR temp gun)
I had heating up issues on hot days(>35°C) and A/C running. 40°+ and A/C off, no issue .. kind'a situation.

Ie. the A/C was putting additional pressure on engine/cooling.
Trying to work out why, I did a lot of normal stuff, and then thought to try other, not so normal stuff too.
I assume you know the run up Pentland Hills. That's my normal test run.
Up the hills, on 35° or higher days, I'd easily see over 110°C on the Tdi, 117°C max with A/C on. About 95-97 with it off .. luckily the downhill run allows the Tdi to cool quickly to try the uphill again.
So the not so normal thing I tried was to remove the grille. Max temp on that same day(maybe hotter than my first two runs) .. max temp on the digital gauge I saw was 92-93(two runs) or so. May have been 95 on other occasions, but that same day I saw 110-117, it then maxed at 93 .. just removing the grille.
Stupid me tho, I also play about a bit with injector fuelling, so don't really get consistent results to offer more consistent changes.
Tdi is obviously turbo and the greater effect I noted with no grille was the drop in EGT, from having to back off much earlier when I got to 720°C, to not seeing more than 690° all the way to the level off section. I think it gave me an additional 15k/h at the top due to having to back off with the grille on.

Not sure on the next bit tho, but I don't think it's just the grille that may have caused these differences. Looking at the dreadful electric A/C fans, I reckon these block more air flow than the grille does .. just that removing the grille helped a bit.
So, even having seen 117° on the temp gauge, the dash gauge barely moved at all .. as you noted I reckon just above the wavy line marks. Mine sits a couple of mm's below what would be a centreline.
This coming summer I'm going to test removing the condenser fans(grille on) and see how that goes. if it helps, I'll then have a look into a couple of 10" replacement fans for them .. maybe even a larger single like the D2 uses. Not a lot of room in there tho.

Comp test and throw us ya numbers man.
Its the first and most critical step at this point IMHO.
If its a head that just got hot you may get away with a gasket change and shave.
You cook it further and you may have to chuck the engine.

Just pull those plugs and get some numbers mate.