I've just got myself a new 940, 1994 sedan, 187K miles, was headed for junkyard... Some amount of neglect, currently runs but overheats, but the body and the interior are good, so I decided to give it a chance. The obvious problem seems to be a major coolant leak, apparently from the water pump shaft (water leaks on the body of the pump from undeneath the pulley). Car seems to have had water in the cooling system for the last few months, possibly more, so things look rusty and dirty in there. Trying to figure out if there's more to the engine problems (blown head gasket??) or if not, which parts would require changing besides the faulty water pump. The leak is quite strong, and once the engine warms up and starts building up pressure it loses water from the block, even before the reservoir empties. Drove the car for ca 40 minutes, it kept overheating (temperature gauge reads just over normal but the old oil on the engine starts smoking -- oil seeems to be leaking a bit too). No signs of water in the oil (haven't changed it, just checked the dipstick), once the dirty water from the radiator gets to reservoir it looks brownish, but this looks more like rust than oil to me. Just trying to figure out a strategy to see if the engine is worth saving and working on. This car is purely a project at this point. Any help with how to get things diagnosed at a reasonable cost would be appreciated. Thinking to replace the water pump, and see if it makes things better but afraid it would be a waste if it turns out the engine is toast... Thanks!
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'98 965

My check engine light has been out for a while, so I decided to take the chance and brought the car for a smog check. Well, it almost passed, except for an 'NO' reading:

HC (ppm)

15 mph MEAS: 12 AVE: 28 MAX: 59
25 mph MEAS: 6 AVE: 16 MAX: 50

CO (%)

15 mph MEAS: 0.05 AVE: 0.07 MAX: 0.50
25 mph MEAS: 0.03 AVE: 0.06 MAX 0.47

NO (ppm)

15 mph MEAS: *719* AVE: 265 MAX: 556
25 mph MEAS: *835* AVE: 221 MAX: 717

Doesn't seem to be too far off the chart, and upon checking the levels on the last time it passed in 2015 (NO 15 mph 539 (!), 25mph 595) whatever condition makes it run hot has been there for a while.

One thing that crossed my mind was that the car was warmed up fully when I brought it in, perhaps having it tested colder could've helped the 'NO' readings?

Of the things on my list that I haven't done yet are: new spark plugs, seafoam through intake manifold, BG cooling system cleaner, which is a little more potent than the Prestone that I ran; clean the EGR valve, clean or replace the PCV system. The car is half way through a tank of gas with BG 44K fuel system cleaner.

Would appreciate any advice on what to do and what not to do; the smog place gives me a couple of weeks to re-check, and the car registration is up in June.

The car has been running OK after I fixed the water pump and the valve cover leak, doesn't overheat, but the needle is pretty much square in the middle most of the time so it may be running a little hot from what I can see.

Thanks!
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'98 965

Thanks all!
I've just got the oil changed, all looked OK (very low oil level though, only ~2.5 quarts have drained, even though I've been adding some just recently). Looks like oil is leaking from underneath the valve cover, and rather noticeably (some oil still on the exhaust manifold). This stuff was smoking when the engine was getting hot... Wonder if it needs a new gasket there, or something else like plugged PCV system could be causing the leak. Looks like previous owner tried to have it sealed with some stuff, apparently unsuccessfully. Pic attached. Will get to the water pump next...
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'98 965

Dear vp965,

Hope you're well. To get an insight into the state of the PCV system, inspect the flame trap (housed between the third and fourth intake manifold runners). If the flame trap - a round plastic part with many small holes - is plugged, that could be a cause of over-pressure, that forces oil past valve cover gasket.

Once you've removed the water pump, also remove the top timing belt cover (two bolts ⎖ & 12 mm, if I recall correctly] and a T-20 screw, on top's reverse side [closest to the firewall]). If there's no sign of oil getting past the cam seal - oil on the front face of the head or within the timing belt case - then the PCV system likely is OK.

A failed cam seal - or one subject to over-pressure - will allow oil into the timing belt case and may also wet the top of the head projection, under which is the water pump.

You might also want to check the underbody. If the oil pan bolts are "loose" - or if there's excessive crankcase pressure (due to a plugged PCV system) - oil can escape there. If so, you'll see it on the under-body. Go gently when tightening oil pan bolts. "Light snug" suffices: the oil pan bolt holes are easily stripped.

By the way, on start-up, how quickly does the oil pressure warning light go out? If the light goes out "instantly" (1-2 secounds), then the bearings likely are in good order.

Hope this helps.

Yours faithfully,

Spook

By the way, any tips on removing the old water pump from the really rusty inlet pipe (the one that runs under the exhaust manifold)? Not much room there to maneuver, and I didn't feel that banging it off would be a good idea...
Thanks much!
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'98 965

Whew, the thing came off with a bit of PB blaster and elbow grease:


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'98 965

Dear vp965,

Hope you're well. Good going!!! Glad to learn no studs/bolts sheared!!!

The amount of corrosion suggests long-term presence of water rather than coolant.

Did you see any evidence of oil at the top of the water pump?

Hope this helps.

Yours faithfully,

Spook

There are some old oil deposits on the top of the pump and directly above it (trying to include pics); not as much as there is around the exhaust manifold (and the leak looks more fresh too).


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'98 965

Dear vp965,

Hope you're well. The black "crud" atop the head's projection is oil that has been "cooked" by heat from the coolant. This evidences either a cam seal leak (seal falure) or the result of excessive crankcase pressure, resulting from the plugged PCV system.

By, the way, the water pump's rear pipe seal came out with the pipe, so remove it. clean the area, and - if time allows - repaint. Clean the face of the head, being sure to remove any gasket residues. The head's front surface should be perfectly smooth. This will ensure a leak-free water pump installtion.

Further, be sure to clean the water pump mounting studs with a wire brush, and then coat the studs with a nickel-based anti-seize, before installing the pump. This will ease removal of the nuts. The new water pump bolts should also be coated with anti-seized.

Hope this helps.

Yours faithfully,

Spook

I got the water pump installed, following your advice and the FAQ instructions... Took me a few tries, looks like it doesn't go on without the bolts inserted into the pump housing, since the top rubber seal is pushing things down... In my memory, the 960 pump was so much easier... Just as the FAQ warns against, had one of the nuts fall into the lower timing belt cover, luckily magnetic pickup tool saved my back there. Will see if the thing won't leak now (keeping my fingers crossed!!) Wonder if it would be worth running a bottle of a cooling system flush (I used Prestone in the past on my V90 which I think helped clean things up and didn't cause any immediate problems -- well, it still suffers from leaks to be sure)
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'98 965

It was suggested to replace the thermostat. Did you replace it?

I took the old one out, put it in boiling water -- it seems to work properly. Didn't look as bad as the water pump of course, just some oxidation and rust deposits... I got a new one coming on Tuesday, will replace it then. A small detail: the current one is a 87 degree, I ordered a 92 degree one as per the owner's manual (I'm in Southern California and it gets pretty hot around here, so I guess 87 degree wouldn't be out of place. Still, I felt I should go with the manual...)
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'98 965

Yes looks like you'd need to flush the system many times over till clear water runs in there. Presence of rust may inhibit heat transfer from engine block (the aluminium head block & lower iron cylinder block) to coolant. Then any rust coating inside the radiator innards could further inhibit heat transfer from coolant to outside air.

Your radiator and head block is made of aluminium so they shouldn't rust but your cylinder block is made of iron. These floating rust particles could end up stuck to innards of the cooling system by heat and water pressure.

Thats the general theory but in actuality you'll know you have heat transfer issue when the radiator fan takes long time to shut off. To me this is an early indication of trouble. In my tropical climate its about 1 to 1.5 mins tops at idle after normal driving. Don't rely too much on the temp gauge as it doesn't show real time temp. By the time the needle goes past centre its already too late.

Hope this helps,
Amarin

Got the car running with the new water pump, ran the Prestone cleaner (keeping fingers crossed). So far so good, no signs of major leaks. The thermostat works (but will put in the new one that arrived). The car warms up quickly (needle stays just under the middle) and the oil which seems to be splashing around (!) from the unidentified leak, starts smoking. Fresh oil on the side of the head below the valve cover gasket, some splashes on the newly installed oil filter, the upper steering pump hose as well as the lower radiator hose. Feels like a fair amount of oil was lost during the few miles that I drove it since the water pump change... Noticed that the radiator fan does not come on except with the AC on (so the fan itself is OK) -- I'll try to troubleshoot the sensors and the fan relay. Gotta check the PCV system, too... Car has check engine code 143 (for the front knock sensor), and the transmission upshifts kind of rough (kicking in late). Feel like the leaking oil, the fan and the check engine light are the priorities right now (lots of other usual issues like brakes, suspension... but we'll get there)
Thanks all!
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'98 965

Dear vp965,

Hope you're well. So far, so good!! A valve cover gasket is not costly, so that should be replaced. I'd guess that the in-service gasket has failed. Inspect the flame trap. Even if the insert (plastic, with many holes) is not plugged, the oil trap (#3501160, about $60 at a dealer) - below the flame trap - could well be plugged. If so, it will have to be replaced.

The tranny's rough shifts could be cured by a flush. I'd use 12 quarts of Wal-Mart automatic transmission fluid (ATF). If that improves the shift - as I'd expect it will - drive for 1,000 miles and then re-flush with Mobil 1 synthetic ATF. It might also be needful to lubricate and to adjust the "kick-down" cable. See the site's FAQs for these tasks.

The knock sensor code could be the result of a damaged wiring harness and/or corrosion interfering with the sensor's signal. I'd remove the sensor - it is secured with a single bolt - and clean the sensor, the block's mating surface, and the sensor's connectors. If that doesn't cause the code to clear, then the sensor may have failed. Few such failures have been reported here in recent years.

Hope this helps.

Yours faithfully,

Spook

I've resolved the valve cover issue, there's no more burning oil on the exhaust (was really bad) so hopefully things are getting better. :)

The 143 code is more persistent -- I've removed the sensor and cleaned it, the code stayed off for about 3 days (and multiple trips) then came back. I've replaced the sensor with a new one (just in case, $30 insurance:) but doubt that would really fix it... From what I've been reading around, replacing the wiring from the sensor to ICU seems to do the trick. I'm wondering if anyone has instructions on how this could be done (trying to find out the location of the ICU and the routing of the wiring which is all a new thing to me)...
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'98 965

Dear vp965,

Hope you're well. If you've not done so, use an electrical connector corrosion-remover (e.g., Deoxit) on the knock sensor's connector. An invisibly-thin layer of corrosion could disrupt the signal to the ignition control unit (ICU), which device is mounted underneath the instrument cluster and is accessed from the driver's footwell.

If cleaning the knock sensor's wiring harness connector does not restore smooth operator, then it will be needful to see if the wires from the sensor to the ICU need to be replaced.

Hope this helps.

Yours faithfully,

Spook

Thank you for the valuable advice!

I verified that the oil leak is indeed from the valve cover gasket: as the engine warmed up the oil was actually spraying from a leak near cylinder 1 on the exhaust side... Ordered the gasket to change..

I checked the flame trap, it wasn't plugged, but the small curved hose underneath the flame trap was cracked open at both connectors (looked like one of the cheap aftermarket replacements -- I ordered another one). I'm inclined to replace the oil trap if I get a chance, ordered an aftermarket one branded by Skandix from eEuroParts.com which costs half of the Volvo one (keeping fingers crossed). The original one seemed to have some crud in the opening, but hard to say how bad without actually removing it...

Looked up some information about the knock sensor, still trying to figure out how to get to it, maybe pulling the intake manifold wouldn't be a bad idea, and this would give me access to the oil trap as well. If there's a fair amount of work involved in getting to the sensor I would consider actually replacing it (the cost is $27 for a Bosch sensor) as well as the wiring (trying to figure out how to do that as well). The engine does sound sometimes as if it would benefit from a 91 octane fuel, but not really bad overall. There's some odd hesitation I think when the AC compressor kicks in... I think the car is a survivor :)
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'98 965

Dear vp965,

Hope you're well. The steel pipe at the back of the water pump - which takes hot coolant to the heater valve - is secured by a single flange screw and a nut.

Once that flange screw has been removed, the pipe should come out of the pump housing. Be sure to remove the oil "O" ring - inside the pump housing - if the "O" ring does not come out with the pipe.

Clean the end of the pipe (paint it, if you've time). The Volvo brand "O" rings have slightly radiused edges and so seat more smoothly than will an aftermarket "O" ring, that has sharp (non-radiused) edges.

I'd also saturate the oil pump nuts and bolts with a penetrating oil (PB Blaster, Kroil, etc.) over a couple of days. It takes time for the oil to percolate through micro-channels in the corrosion, and so to weaken corrosion bonds.

See the site's FAQs for tips on water pump replacement.

Hope this helps.

Yours faithfully,

Spook

Before you do the water pump, look at cylinder head pressures to find out if you have a head gasket issue.

I had an 89 740 & one extrememly cold day,,as it was warming up I went in the cafe to get coffee,,,when I came out the temp needle was all the way in the red!!! thinking the fan was bad I drove it downhill back home & it cooled off so I got some block seal for about $15 & followed the directions exactly!
Drained the system flush w water & drained some then filled w the block seal

ran for 15 mins shut it off,,,,let sit an hour & then ran for 30?? let sit for an hour ,,,5 hrs later ran for an hour,,,,,,not sure of the time,,,
But I took the plugs out & let it sit overnight,,,put it back together,filled w coolant,& ,It ran for another 3 years no problems!!!

Replace thermostat and water pump like Spook had mentioned. While doing these replacements, use running water (eg. from a garden hose) to flush rust out of radiator, engine and coolant reservoir. If you look under the exhaust manifold no.4 there's a brass drain plug which you could open to aid more rust drainage from engine block. Use a 13mm wrench. Careful not to lose the plug (hard to get by). When finished just tighten till no more water comes out. Don't over tighten as its made of brass.

Regards,
Amarin.

If all the usual causes of overheating have been eliminated, what's left is a leaking head gasket.
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1992 745, >500k km (now gone, but not forgotten)

Dear vp965,

Hope you're well. I'd replace the water pump and thermostat and refill with fresh coolant. I'd also change the oil and filter. None of these tasks is very hard or costly. Once you've drained the old coolant, fill and empty the cooing system a couple of times with ordinary water, until drained water runs clear. Then, re-fill with 50/50 mix of coolant and distilled water.

If the oil shows no signs of water infiltration - i.e., if the oil is not milky - and there's no steam coming out of the exhaust - the headgasket is likely OK.

Further, if the engine runs smoothly - despite the coolant leak - that's another sign the engine is in good order.

Hope this helps.

Yours faithfully,

Spook