Advice needed - oil in coolant - 940 LPT Auto

[Ltom]

Hi all, unfortunately I'm in need of some good advice.

I have a 1998 940 Estate Automatic 2.3 LPT with 185k miles on the clock. I bought it a few months ago from an indie Volvo garage who had done the timing belt, front cam seal, and various other stuff including transmission oil change.

The other day I found oil in the coolant reservoir. I think it's ATF as when I dip my finger in and blot it on some paper, it's more red than brown. I gather that the usual culprit is the ATF oil cooler in the radiator. I'm planning on replacing the radiator and flushing both the coolant and transmission fluids, also I'll replace the reservoir because it's gross.

So my questions are: how should I go about flushing the coolant system (which will have oil throughout) and how can I do a complete flush of the transmission. The Haynes manual says that a drain and refill is 3.9 litres but from dry is 7.5 litres (for the AW71 gearbox). How can I ensure that all the ATF is replaced? I have driven hundreds of miles in the past few days so I'm worried about having damaged the transmission, but there are no symptoms noticeable when driving (gear shifts, overheating etc).

Should I be worried about a possible head-gasket fault as well? I had some blue combustion leak test fluid but it was labelled for diesel not petrol if that matters. I put the s bend with tester fluid on the header tank and idled the engine for 10 minutes from cold. One bubble came through every 5-10 seconds but the first bubble took about a minute. The fluid stayed quite blue, maybe went turqoise after the 10 minutes but didn't go full green or yellow.

More context:

While poking around the engine bay I noticed the water pump is weeping coolant from (I think) a rubber o-ring not the gasket to the block. Water pump seems noisy to me but I don't know what's normal.

A month or so ago I was having an issue with a low idle on startup. I replaced the air filter and found lots of oil in the air intake hoses so I also cleaned and checked all the vacuum hoses from the throttle body to the crankcase oil box thing and cleaned the MAF. That seemed to fix the problem.

Any help and advice would be greatly appreciated.

[Forrest]

Welcome to the joys of classic Volvo ownership.

The method I use for a thorough coolant system flush is to disconnect the bottom radiator hose at the radiator and remove the thermostat, temporarily replace the thermostat housing, stick a garden hose in the bottom hose facing towards the water pump and run both the hose and the engine until the water flows out of the bottom of the radiator clear. Remember to have the heater control set to maximum heat to get water to flow through the heater matrix.

Google Gibbons Method for a similar approach to flushing the automatic transmission fluid. If the fluid is heavily contaminated it will be advisable to drain the pan, refill and run for a bit first to avoid shocking the system with brand new fluid. If you employ this method you will need considerably more fresh fluid than the capacity of the system. I usually use at least 2.5 gallons.

If your car has had a recent top camshaft seal the oil leak that preceded this is almost certainly responsible for the failure of the water pump top seal.
Replacing the water pump is quite an easy DIY task as it does not involve disturbing the timing belt. There is a bit of a knack to compressing the top gasket correctly and getting the heater bypass pipe to seal. I find the latter is best achieved by fitting the gasket onto the pipe dry and greasing the outside edge of the gasket and/or the hole in the back of the pump. I tend to use o-ring grease to encourage this gasket to swell a bit and create a more effective seal. Before refitting the pump with new gaskets ensure all the mating surfaces are completely clean with no traces of corrosion or old gasket otherwise you will get leaks straight away. I use a Dremel with a brass wire brush for this.

The biggest clue to HG failure is a smell of exhaust and retained pressure in the coolant header tank when cold. If you're getting this then the excess pressure is quite likely to be causing coolant leaks that you wouldn't have if the cooling system were working normally. Your car is at about the right mileage for its first HG failure. Is there any record of it having been replaced before?

I won't pass comment on your low idle on startup problem. If you read my recent saga you will see I'm still struggling with a similar problem combined with misfire and serious lack of power.

Good luck getting your issues sorted out. These cars are well worth the effort when they're working well. Many on here will sympathise with it seeming like everything is failing at once.

[Ltom]

Thanks for the info on the flushing procedure Forrest, I've ordered the parts and I'll let you know how I get on.

I talked to the garage I bought the car from, there was no service record of a head gasket change and they didn't do one either. That said, no matter how hard I try, I can't smell exhaust gases in the header tank. All I can smell is the ATF so I'm going to fix the problem I have right now and keep an eye on the coolant level afterwards.

According to the garage, it's very rare for coolant to mix into the ATF and the ATF looks clear to me. I'll drain a sample off the bottom soon but for now I'm not going to worry too much about the transmission either.

I've ordered a new radiator and header tank, and as a "while I'm there" job I'm going to replace the water pump and all the gaskets and seals. Fingers crossed that's the extent of it for now.

[Laird Scooby]

What's the mileage on your car?

I'd be reluctant to do a flushing change to be honest unless it's a brand new car.

Invest in one of these :

https://www.ebay.co.uk/itm/12V-60W-E...K/164476100325

Drive the car 5-8 miles to get the ATF hot, find an old 5L container (screenwash ones are good as they're clear) and park the car so the back end is higher than the front - use ramps if necessary.

Switch off and remove the ATF dipstick, insert the suction hose from the pump down the dipstick tube as far as you can, might take some wiggling to get it all the way. Arrange the discharge hose from the pump so it flows into the empty 5L container, connect the battery clips and switch on for a few seconds then off. Repeat this every few seconds until ATF starts to flow then leave it on. Go and have a coffee.

Come back after ~20 minutes and wait until the pump start scavenging then switch off, remove the battery leads, remove the suction hose from the dipstick tube and the discharge hose from the 5L container, refitting the lid to the container as you go. Put it somewhere upright so it can settle - this might be important!

Refill the transmission through the dipstick tube with about the same amount of fluid as came out - guess at how much is in the container and put in about 0.5L less than your guess. I use this stuff :

https://www.ebay.co.uk/itm/Carlube-A...L/233257297843


Start it up and get it level then check the fluid level and top up to the cold mark (the lower set of markings on the dipstick) then give it a test drive for 5-8 miles, return and check/top up the level.

Now check the 5L container. If there's any water/coolant in it then it will be visible under the ATF. Repeat this 2 or 3 times at monthly intervals until the fluid stays clean then do one part-change a year/12k miles to keep it fresh.



Cooling system, set the heater to hot, remove the thermostat and refit the 'stat housing. Remove the top hose from the radiator stub and put the garden hose in there (most Hoselock style fittings fit snugly into the top hose) and turn it on. No need to run the engine. This will backflush the system, removing any gunge that is lodged in various paces because the normal direction of flow is holding it there.

Once fully flushed, refit the 'stat and housing and the op hose. Add some coolant flush (Comma do some good ones) and add that to the expansion tank and top up with fresh water. Take it for a drive as directed on the bottle of flushing agent but double the time.

Return and allow the engine to cool. Now repeat the flushing above so the engine is again backflushed. This normally takes about 30 minutes for the water to run clear from the stub on the top of the rad.

Once it runs clear, turn the garden hose off and remove it from the top hose, refit the 'stat and housing again, refit the top hose. Now remove the bottom hose from the radiator to drain the majority of water in the system then refit.

Add ~5L of ethylene glycol (normally blue or green - DO NOT USE THE HORRIBLE RED OAT STUFF!!!!!

Now top up with water to the level. Get it warmed up either by fast idle at home or taking for a drive, park facing up hill if possible on your return and let it cool overnight. Check the level and top up to the Minimum mark with clean water (you already have enough antifreeze in there) if needed.

This method has worked for 30+ years for me with no problems and has given me the correct concentration of antifreeze as well.

[Dippydog]

When the engine oil cooler let go and mixed oil and coolant on my V6 Omega I used laundry liquid to flush the cooling system.

[Ltom]

UPDATE:

I changed the radiator, header tank, and water pump. A surprisingly easy job to do with minimal tools. When I had drained it all out there was no sediment in the system and hardly any oil. The small quantity ATF just looks really bad in the header tank (there was even some mayo) but there isn't that much. Maybe 30ml in total. I decided not to use any detergent and I didn't have the facilities to flush (I'mnot at home) but since i was replacing the whole rad and emptied all the hoses I don't think it matters.

I replaced with new coolant and the car has been fine since. I was warned that the oil can cause the hoses to swell but I think I caught it soon enough, they seem fine.
Two things to anyone doing this job:
1. If you replace the header tank hoses, make sure you get the right variant. The non-AC variant is 1 inch too short! But the correct AC variant is twice the price.
2. Annoyingly one of the water pump bolts is behind the timing belt cover so that has to come off (only the top half).

[Laird Scooby]

Originally Posted by Ltom

UPDATE:

I changed the radiator, header tank, and water pump. A surprisingly easy job to do with minimal tools. When I had drained it all out there was no sediment in the system and hardly any oil. The small quantity ATF just looks really bad in the header tank (there was even some mayo) but there isn't that much. Maybe 30ml in total. I decided not to use any detergent and I didn't have the facilities to flush (I'mnot at home) but since i was replacing the whole rad and emptied all the hoses I don't think it matters.

I replaced with new coolant and the car has been fine since. I was warned that the oil can cause the hoses to swell but I think I caught it soon enough, they seem fine.
Two things to anyone doing this job:
1. If you replace the header tank hoses, make sure you get the right variant. The non-AC variant is 1 inch too short! But the correct AC variant is twice the price.
2. Annoyingly one of the water pump bolts is behind the timing belt cover so that has to come off (only the top half).

Good news, i strongly suggest you change the ATF as well, at least do a part-change now and another in a couple of weeks. Either use the drain plug in the sump or a 12V oil transfer pump (less than a tenner on ebay usually) to drain the gearbox sump, i'd also suggest using :

https://www.ebay.co.uk/itm/Carlube-A...L/233257297843

I use a pump, have the back end higher (on ramps usually) so the ATF runs to the front of the box, feed the suction pipe down the dipstick tube to the bottom and arrange the discharge pipe to go into a clear 5L container then connect the pump to the battery, switch on/off a few times until the ATF starts flowing then leave it on and go for a coffee.
Return 20 minutes ish later, wait for the ATF to finish pumping then switch the pump off, put the lid on the 5L container and put it to one side to settle, guessing the amount that came out.

Remove the pump and add a little less than i guess came out of fresh fluid. Back on level ground, start the engine and let it idle, move the shift lever through all positions at least twice, returning it to P then check the level. Top up to the Cold mark (one side of the transmission dipstick is lower than the other, this is the cold side) lower level then take it for a 5-8 mile drive. Recheck the level (hot side this time and top up to at least the minimum but nearer the maximum.

Repeat after a month at least twice usually but in your case because of the probability of coolant (you can see this at the bottom of the 5L container once it's settled) in there, i'd do it after 2 weeks until you're not getting any more coolant out. Once the fluid stays clean in between part-changes, just do one part-change every 12000 miles/12 months to maintain it in good to excellent condition.

[Ltom]

Dave I thought that the direction is always oil to water and that no coolant gets into the ATF? I would do the flush but I'm not at home and have no access to a workshop or even level surface.

[Laird Scooby]

Originally Posted by Ltom

Dave I thought that the direction is always oil to water and that no coolant gets into the ATF? I would do the flush but I'm not at home and have no access to a workshop or even level surface.

That's a myth i'm afraid. The ATF going through the heat exchangers in the rad is what's known in hydraulic terms as "RTT" - Return To Tank - and as such has no pressure behind, it, just flow.

Now consider the cooling system - on top of the expansion tank is a pressure cap, most are rated at 1.1 or 1.5 bar - 16 or 23psi - much higher than the pressure of the ATF so you can see what's going to happen!

My last SD1 V8 suffered that fate, when i say it was immaculate and had a superb engine, it was about 8-9 years old at the time and had been maintained regardless of cost - it had a new pair of Nivos on the back (even then they were £700 for the pair) and the seller sold it to me for what the Nivos cost him.
I'd been offered £2-3k for the car but didn't want to sell and then the gearbox went. Spent a very wet weekend changing the box (not realising at the time what had caused it) and all was good for another few months but by then i'd been made redundant and had just started another job so taking the friday and saturday morning off because my car had died wan't an option. Did a trade in for a Chevette that developed a dodgy clutch after 2 weeks plus some cash and the trader took my Rover away - put another gearbox and rad in it and sold it for £2795!

That bit of waffle is just to highlight that the problem does exist and can cause failure of the gearbox.

https://www.ebay.co.uk/itm/12V-60W-E...K/164476100325

One of those, park facing downhill, an empty 5L clear container for the old ATF plus a tub as linked to above and you don't need to crawl on the deck, do the job in about half an hour then repeat in a couple of weeks to ensure you get any coolant out of the box and you should be ok. Barely even get your paws dirty too!

[Ltom]

Oh no, why are all the things I want to believe myths!

Sounds like I need to do it, the coolant can't be good for the gearbox. I did the last job in the church car park of the French village where I'm staying so I might need to buy a set of rosary beads to go with the pump haha.

Also side question for you Dave since you know about this stuff. How on earth do you get the rear bumper off? I have a repair kit and it was supposed to slide off but it catches on the wheel arch and will not come off. It was so stubborn I decided that it wouldn't fall off and left it but I should really get around to it.

Cheers, Tom