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Old 08-25-2020, 08:45 AM   #1
G-Tech 940
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Default 940 - Chasing Coolant Leaks

I have been chasing coolant leaks in my 940 since I changed the coolant.

The hose clamps seem to loosen over time. I frequently come out in the morning to find a few oz of coolant on the ground. This morning it was the entire overflow bottle.

It has now decided to leak from the oil cooler area. Bad news as I dont have the 7mm wrench needed to access those hose clamps. (I probably could have rotated the clamps better when putting the coolant system back together)

What is the proper solution to end the leaks permanently? Replace the hoses? Replace all the clamps? Just keep tightening?
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Old 08-25-2020, 08:53 AM   #2
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Are the leaking hoses soft? Check the health of those hoses, especially the oil cooler hoses. The clamps are probably fine if they're not rusted. If it keeps leaking from new places after a few rounds of tightening, do one of those head gasket tests.
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Old 08-25-2020, 10:55 AM   #3
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Are the leaking hoses soft? Check the health of those hoses, especially the oil cooler hoses. The clamps are probably fine if they're not rusted. If it keeps leaking from new places after a few rounds of tightening, do one of those head gasket tests.
All of the hoses are squeezable, I'm not sure how much softness is bad. One of the oil cooler hoses had clearly been replaced once before, with a hose that had a much firmer and fabric wrapped exterior.

What is a headgasket test? I have done a compression test. All the numbers were quite good. I was using a 60 year old tester though, I didn't want to crank the compression test hose too tight into the plug hole so there was a bit of a 'leakdown' after the 155-ish compression numbers were reached. They were similar rates of leak across all 4 cylinders though so I chalked it up to my tester rather than a HG blown in the similar manner on all 4 cylinders.
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Old 08-25-2020, 11:01 AM   #4
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Default 940 coolant leaks

I'm amazed that there are so few posts about this problem. I kept wondering how much technical knowledge I need to tighten down a hose clamp? My 940 had an intermittent leak at the lower hose/water pump. The coolant drips down on top of the power steering pump. New (aftermarket) hoses, new (aftermarket) water pump, Volvo style hose clamps. You definitely need the high quality hose clamps.



Another problem child is the thermostat housing. On 940's the housing will probably show signs of corrosion and pitting where the hose connects. Replacement from IPD.


After a lot of time wasting I am now using permatex black or blue sealant on the hose connections. Smear it on the fittings and on the inside of the hose. Let it get partially dry (2 hours), install hoses, let dry over night. Problem goes away.



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Old 08-25-2020, 11:19 AM   #5
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It's always a good idea to replace hoses, especially if there are leaks and you aren't sure how many miles they've seen.

With the hose off, inspect the hose fittings on the radiator: often the metal is no longer perfectly round on the radiator fitting, due to over-tightening in the past.

If a fitting is out of round then bring it back to its correct shape first, before affixing a hose to it.

The metal is surprisingly pliable and capable of being deformed / reshaped.
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Old 08-25-2020, 11:21 AM   #6
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Originally Posted by Lazarus View Post
I'm amazed that there are so few posts about this problem. I kept wondering how much technical knowledge I need to tighten down a hose clamp? My 940 had an intermittent leak at the lower hose/water pump. The coolant drips down on top of the power steering pump. New (aftermarket) hoses, new (aftermarket) water pump, Volvo style hose clamps. You definitely need the high quality hose clamps.



Another problem child is the thermostat housing. On 940's the housing will probably show signs of corrosion and pitting where the hose connects. Replacement from IPD.


After a lot of time wasting I am now using permatex black or blue sealant on the hose connections. Smear it on the fittings and on the inside of the hose. Let it get partially dry (2 hours), install hoses, let dry over night. Problem goes away.



Lazarus
Appreciate your response, I have been tightening and tightening.

Do you think it'll be enough to keep all my hoses and OE clamps, and re-seat them all using Permatex Ultra Black? (I already have a tube of that). I would really like to avoid changing my hoses right now, do88 blue silicone has been calling my name for a while but I need to hold off!

My thermostat housing is a tiny bit corroded and does leak very slowly, but I'm okay with that for now. My bigger issue by far comes from the hoses themselves.

I have read recommendation to change the green coolant cap (150kPa I think) for an older grey 240 cap. My green cap is brand new. I didn't really want to change the cap as I thought that the system needs the proper pressure to cool properly. What are your thoughts on this?
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Old 08-25-2020, 11:54 AM   #7
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Most people hate them; but, there is a reason most OEM's use those spring steel clamps on radiator hoses. They have the great advantage that they are able to maintain some clamping pressure on the hose as the hose rubber deforms under pressure of the clamp. With a screw style clamp, as the hose rubber 'oozes' out from under the clamp, clamping pressure is lost and you get the inevitable leaks from loss of clamping pressure.

If you are using screw clamps, most new hoses will develop leaks it a couple of weeks of use after some heat cycling and hose deformation. The severity of the problem will depend on the hoses and the durometer value of the rubber. Stiffer rubbers are probably less susceptible to deformation and leaking; but, are harder to install. I installed all new coolant hoses on my B20E and I was checking clamps for a couple of months to deal with leaks. I am a bit surprised that your old hoses demonstrate this problem because you would expect that the rubber has already deformed and that there should be no further relaxation in the rubber as long as the clamp goes back in its original location.

When you removed the hoses originally, did you use something like a screwdriver or other sharp / hard object to break the seal of the hose on the outlet and help pry it off? If so, is there a chance that you nicked or gouged the outlet spigot? If so, it is likely that fitting is going to weep forever. However, the fact that your clamps seem to be coming loose does seem like a hose rubber deformation problem.

There are toggle screw style clamps that are spring loaded so they attempt to maintain a constant pressure on the rubber as the rubber deforms. Unfortunately, they are about 10x the price of ABBA banded clamps and I have never seen them in small sizes. You could also try fitting the hateful spring style hose clamps; but, you have to be precise with sizing them (no one size fits all!).

I would not use sealant on the hoses. If the sealant works it will be agony when you or the next owner goes to replace the hoses.

Silicone coolant hoses are a poor choice for a daily driver car. Silicone has a high temperature resistance; but, silicone is permeable to water which means that you will have continual low loss of coolant through the walls of the hoses. You will be living in the land of perpetual top up.
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Old 08-25-2020, 02:30 PM   #8
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Originally Posted by 142 guy View Post
When you removed the hoses originally, did you use something like a screwdriver or other sharp / hard object to break the seal of the hose on the outlet and help pry it off? If so, is there a chance that you nicked or gouged the outlet spigot?

I dont think I used a screwdriver anywhere to get hoses off. I found the best way was to gently twist the hose until it rotated, then gently pull it off.

The only thing I could think of like that is I used a wire wheel to take off all the corroded gunk that was on the pipe end. Looked like just coolant crud though, no rubber. I didnt leave any visible scratches anywhere.


I'm going to order some new oil cooler hoses and clamps from Volvo and swap them out. I dont mind tightening up a few higher hose clamps now and then, but the oil cooler ones are a pain in the ass, I might need to take off the oil filter to access the hose clamps :(
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Old 08-25-2020, 03:16 PM   #9
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Let's don't rule out possible Electrolysis Corrosion, which can attack rubber hoses.

"Radiator and heater hoses can also fail from the inside out due to electrolysis corrosion. Rubber is normally non-conductive so you would think this would be impossible. But the coolant can react electrochemically with the synthetic rubber, causing it to degenerate, pit, crack and eventually fail. If you cut open a hose that has failed because of electrolysis, the inside will usually have fissures, cracks and pits created by the electrochemical attack."

From "Cooling System Electrolysis Corrosion"

Also gives methods for testing for electrolysis.

Just out of curiousity, check the inner surface of one of the problematical hoses. Scrape a finger along the inside of the hose, beyond the clamping area. If it comes out black and slimy the hose has degraded and needs to be replaced.
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Old 08-25-2020, 03:35 PM   #10
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I was finally abler to stop my 740 turbo from leaking coolant after I replaced all the hoses (heater core hoses as well) and clamps, bought a new thermostat housing and thermostat, and cleaned off all the pipe ends, like G-Tech 940 mentioned. Been driving 740 Turbos since 2002, and I did this to my current 740 6 years ago and it's still leak free. FWIW I also use a black coolant overflow cap, 1 step lower thermostat, and run water wetter to help deter ping because of higher boost (13 psi on a 13c).
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Old 08-25-2020, 03:40 PM   #11
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The test I meant was for exhaust gases in the coolant. When my head gasket failed it was an exhaust to coolant leak which kept popping hoses. 155 isn't bad at all though.
Twisting the hoses off is the best way I know to remove them safely, so you're doing that right.
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Old 08-25-2020, 05:25 PM   #12
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Quote:
Originally Posted by tintintin View Post
Let's don't rule out possible Electrolysis Corrosion, which can attack rubber hoses.


Just out of curiousity, check the inner surface of one of the problematical hoses. Scrape a finger along the inside of the hose, beyond the clamping area. If it comes out black and slimy the hose has degraded and needs to be replaced.
There was definitely electrolysis going on in the area, as I think that is what most of that coolant crud on the pipe nipple was.

I didn't see any black "slime" but there did seem to be a bit of degradation somewhere as I noticed a small amount of some black dust and chunks in the coolant, after flushing pretty well.

I can't afford to do a whole swap right now I don't think, but I will replace the oil cooler hoses and clamps. Some hose clamps are not available from the dealer. Are these really vital to replace? Or is it more about getting refreshed hoses?


What is the consensus regarding silicone vs rubber? I hadn't heard of coolant weeping through the silicone until a few comments ago. Do people tend to mostly use silicone just for air hoses?

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Old 08-25-2020, 07:07 PM   #13
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The water is absorbed through silicone hoses, so the coolant concentration increases and the level drops over time.
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Old 08-25-2020, 07:18 PM   #14
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Originally Posted by iamrolling View Post
The test I meant was for exhaust gases in the coolant. When my head gasket failed it was an exhaust to coolant leak which kept popping hoses. 155 isn't bad at all though.
Twisting the hoses off is the best way I know to remove them safely, so you're doing that right.
Thanks, I hadn't thought of doing the exhaust gas test, I'll give that a shot after finishing the hoses. I had someone who was going to buy the car tell me it had a blown HG but I didn't know how he could tell, I could see no signs of one, coolant and oil were clear, didn't see any bubbles in the reservoir, etc. I figured he was trying to scare me into selling it to him or something.

Quote:
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The water is absorbed through silicone hoses, so the coolant concentration increases and the level drops over time.
Ohh okay I understand now, it's only the water that is passing through and not the coolant. I will stick with Volvo hoses (they are cheaper than do88 anyways) for coolant.

I had a look on FCP for the hose clamps, they are quite expensive and apparently not OE, instead they are the NORMA brand made in Germany. I imagine there is a cheaper place to get these clamps from, but ebay is very expensive. I'm on board with using good clamps, but getting them at the best price would be ideal. Any ideas where to source them?

EDIT: Found them on Amazon for cheap! Boxes of 10 though.

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Old 08-25-2020, 08:16 PM   #15
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One thing I did was replace the matrix oil cooler with a proper remote oil cooler from a 1992 - 94 960, if you can find one of course, they are becoming somewhat uncommon. It is mounted width wise under the radiator, there are mounting points on the late 940s so quite straightforward. One has to install an earlier 740 oil filter housing with the inlet/outlet for hoses as well as either a 240 or 740 NA or turbo for the coolant pipe coming off the back of the water pump as well.

A bit of work but worth it, the larger radiator in the late 940's necessitated this or one could have used the oil cooler from a 740T, of course there is always an aftermarket version as well. I truly dislike those coolant fed oil coolers as the hoses are subjected to a lot of heat and usually a degree of oil contamination over time and they can also leak ( the matrix ) internally, nothing like coolant and oil mixing together.

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Old 08-25-2020, 10:01 PM   #16
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Check out the hoses at the oil cooler if yours is oil to coolant. The "U" and "L" hoses are easy culprits of being bad without being obvious.
IPD sells em, and if yours don't look new-ish I'd replace for preventative measure. I think I've got the right ones linked.

https://www.ipdusa.com/products/7025...t-6065-9161384
and
https://www.ipdusa.com/products/7024...t-6064-9161383
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Old 08-25-2020, 11:02 PM   #17
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Even if there is a head gasket problem, don't worry. It's a piece of cake.
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Old 09-03-2020, 08:14 PM   #18
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I ordered a full set of hoses from Volvo, and a bunch of NORMA clamps that should replace most of the connections.

I also found that thread about replacing the OE heater valve with the GMC Safari Van part, so I ordered one (was Four Seasons brand but identical) to pop in.

Will be nice to not have to carry around a jug in my trunk to top up every few km!
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Old 09-10-2020, 05:36 PM   #19
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Replaced all the coolant hoses with Volvo hoses.

Replaced all the clamps with good clamps.

Replaced the Heater Valve with the Four Seasons part for the Safari Van.

Nothing leaks! Except the ****ing Block Heater. That must have been what was leaking this whole time. I feel like an idiot for missing it, but I thought it was the aftermarket oil cooler hose right below it. The block heater is non functional, I cut off the power cord months ago (it was falling apart).

How do I go about sealing this up? I understand there is a plug that I could use to replace it, but I don't see it on the parts diagram. Closest I can find is either 968144 or 946559.
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Old 09-10-2020, 10:28 PM   #20
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okay, some more research has me looking at either replacing the block heater for $160, or the freeze plug with potential for more leaks for $5.
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Old 09-11-2020, 02:55 PM   #21
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How much of a pain is it to get in there? If it's easy, I'd do the freeze plug (cleaning up the area as much as possible to help it seal)... worst case you're out $5 plus the cost of a coolant drain and refill.

I'm presuming you don't need the block heater despite being in Canada, since you have been without it for a while. It might be a future selling point for the car if you can get a modern one.
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Old 09-11-2020, 03:15 PM   #22
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How much of a pain is it to get in there? If it's easy, I'd do the freeze plug (cleaning up the area as much as possible to help it seal)... worst case you're out $5 plus the cost of a coolant drain and refill.

I'm presuming you don't need the block heater despite being in Canada, since you have been without it for a while. It might be a future selling point for the car if you can get a modern one.
For someone like me who works slow and methodical, its a several day job. I am pretty sure ill have to pull the exhaust manifold and turbo, downpipe, the coolant hard line, the oil filter.

I might be able to get away with leaving the manifold in and only removing the coolant hard line and oil filter.

My engine has the cup style freeze plugs (which I found a new one among my parts stash) which seem to be held in with either loctite #1, or a gasket material, (I read grey so I would use Hondabond), Permatex Aviation, or even JB weld.

https://www.fcpeuro.com/products/vol...-volvo-3531239

I don't really need a block heater as it's a summer car. Even still, the winters around here are pretty mild for cars and most people don't use a block heater (although I do have and use one on my winter Subaru on the coldest days only).

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Old 09-14-2020, 04:37 PM   #23
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So I got up in there today and pulled the oil filter off, the oil cooler hoses, and the hard coolant line.

The screw was loose on the block heater but I am doubting that it is the block heater anymore. It looks like it is coming from higher up, and the only thing higher up is the headgasket... I still want to pull that block heater out if I can, I already spent $30 on dry ice for the expansion plug (and thus have also give myself a time limit to work against)

Is it likely on a B230 that the HG is dripping so much coolant? It empties the overflow bottle after a short drive or overnight. I am in the middle of removing the exhaust manifold (and turbo and downpipe) to check it out closer. I can't get the hard coolant line out to inspect it yet but it is the original from 1992, it seemed fine when I had it out 2 months ago. I can't figure out where the heck else it would be leaking from.
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Old 09-14-2020, 04:57 PM   #24
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Yes, the head gasket can leak that much through a crack in the gasket. A customer of mine just left in his 940 that has this problem. On his car you can clearly see the trail of coolant coming down the side of the block right next to the oil separator box. His car has 350,000 miles on it and has bad blow by on the rings. It isn't worth doing a head gasket on it. I sent him to the auto parts store with a picture of a bottle of Bars Leak sent to his phone. The Bars Leak might buy him some more time with the car. Another customer of mine drove his 940 for over a year with a minor head gasket leak out the passenger side below exhaust port # 4. He finally brought it to me and had the gasket replaced. The gasket out of that 940 had a crack in it that looked like the gasket had been cut with a razor blade. The Bars Leak would plug it fine for 2-3 weeks, then, it would leak a small amount of coolant and seal itself back up.
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Old 09-14-2020, 05:17 PM   #25
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Well, I guess I will either have to use a bottle of this stuff, or just try to replace the HG myself.

I'll probably attempt the HG as I already have an Elring HG and Mahle Head Bolts on hand, and am halfway to having the exhaust manifold removed.

Thank you!
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