BMC 1.8 Engine Oil in Heat Exchange?

[Megafugle]

Hi,

 

Was hoping someone might be able to assist me with an issue I am having. Ive recently bought a new cruiser and inherited a 1.8 BMC marine diesel engine. I am having an issue with overheating and I think this is related to the heat exchanger.

 

The issue I am having is that the heat exchanger requires a top up of nearly 3 litres for every hour or so of being used. This clearly seems excessive to me but I can not see the problem. The engine starts fine first time but I am assuming it has a leak somewhere?

 

There also appears to be an oily substance in the heat exchange itself which would seem unusual as I am topping it up with water only at the moment. 

 

Was hoping someone might be able to assist me with diagnosing the issue, I have a rudimentary knowledge of this engine but please treat me as a layman!

 

Thanks

 

 

 

[Tony Brooks]

It seems to be a Z drive/outdrive boat so I doubt it uses a gearbox oil cooler and it is a heat exchanger cooled boat so any oil cooler or drive cooler pipework should all use raw water. That means that a fault in any cooler circuit should not be able to lose the actual engine coolant. In any case I can't see any signs of oil in the manifold/cum heat exchanger.

 

Do you fill the header tank to the brim? If so you are overfilling it. As on a heat exchanger boat the coolant volume is known so an inch below the filler neck should be about right. However, that is equal to far less than 3 litres.

 

At present, in the absence of any leaks, I can only conclude the heat exchanger core in the manifold is punctured so when the coolant pressurizes it is blown into the raw water circuit.

[Quattrodave]

Agree with Tony.  Check the raw water pump impler.  They wear and fall apart to the point where there is no cooling... I take it you have a wet exhaust, is there plenty of water coming out??

[Tony Brooks]

10 hours ago, Quattrodave said:

Agree with Tony.  Check the raw water pump impler.  They wear and fall apart to the point where there is no cooling... I take it you have a wet exhaust, is there plenty of water coming out??

 

That is vital. I must confess that I assumed the OP would have checked the raw water system, inlet strainer, something sucked over the raw water inlet skin fitting, volume of raw water from the exhaust, and if all that is OK the impeller in the raw water pump and its drive belt. If the OP does not know it looks as if his raw water pump is mounted below the alternator.

 

Completely off topic and FWIW, the fuel filter mounting bracket looks a bit thin to me and I know a thin mounting bracket on 1.8s can allow the filter to vibrate badly and snap the leak off pipe. The filter end of the leak off pipe looks to me as if it has been annealed, plus it has an anti-vibration loop. Once the OP has sorted his cooling problem I would suggest that he takes that bracket off and has a  full width & height fillet welded in the centre to stiffen it up.

[Megafugle]

Hi both,

 

Thanks for your replies.

 

Can confirm there is water coming out of the exhaust from the raw water. Its been checked for any blockages and the weed catcher has been emptied and cleared. Interestingly, the water in the heat exchange only drops a little when the boat is left overnight, but a lot when she is moving. Presume this leads further weight to the argument the coolant is leaking into the raw water system?

 

The raw water impeller has been mentioned a couple of times so I will check this next and if necessary replace. Is this the sort of thing I need to buy?

 

https://www.asap-supplies.com/products/jabsco-flexible-neoprene-pump-impeller-spline-drive-12-blades-jab-1210-0001-p

 

I can youtube a video of how to replace it, but for my guidance, would this be considered a fairly simple job or am I better off calling someone in to do it for me? I would estimate my level of expertise as about a 3/10...

 

Thanks

 

PS Thanks again for the observation regards fuel filter mounting. It looks like my list of things to do is growing!

 

[Tony Brooks]

38 minutes ago, Megafugle said:

The raw water impeller has been mentioned a couple of times so I will check this next and if necessary replace. Is this the sort of thing I need to buy?

 

https://www.asap-supplies.com/products/jabsco-flexible-neoprene-pump-impeller-spline-drive-12-blades-jab-1210-0001-p

 

Only if your pump number is one of those listed. It is often on the backplate if it is a flat disk of bras but if the backplate also forms a rear shaft bearing it will be else where. If you can't find the number take the impeller to  a river or sea chandlery, and they should easily match it. Although the size and number of wings may be the same how the shaft drives the impeller can differ. On that size pump it is usually splines but might also be a key in the shaft.

 

PS if you are leaving the coolant hot it will contract as it cools so the level will drop a little overnight.

Edited July 4, 2022 by Tony Brooks

[Quattrodave]

12 hours ago, Megafugle said:

Interestingly, the water in the heat exchange only drops a little when the boat is left overnight, but a lot when she is moving.

 

I may well be mis understanding this but when you're moving the engine will be either hot or warming up quickly..  the coolant system is a closed loop and should pressurise, you shouldn't really be opening rhe coolant when it's hot....

[Megafugle]

Apologies, to clarify. The water in the heat exchange is low/empty once we have been out for a drive, come back, waited for the engine to cool down and then checked the coolant levels. I dont open it when we are underway.

 

Ive also now noticed that the raw water exhaust is not spouting out any water. It was yesterday I promise! As such, most people have suggested I check the impeller. For my understanding, I presume the brass plate in the pictures below is the impeller? Ive looked at a few videos and they seem to suggest I simply remove the brass plating, pull out the fan part and then replace. This looks easy enough in the videos I have seen yet my impeller seems to be in a position where I cant possibly unscrew the screws due to proximity of the black metal plate.

 

Im not sure how to proceed.

 

 

[Quattrodave]

Yes, take the brass screws from the brass plate, remove the plate and rhe impeller should pull out.  Be careful when installing a new one all the lobes need to be pointing the correct way.

 

Edit.  The front plate usually has a pump number on it so you can get rhe correct impeller...

 

Reference the coolant level dropping, you have a leak somewhere.  If you can't find a weep check rhe coolant pump shaft... if you have a mitivac you can pressurise the coolant system with out getting it hot!!! It's often easier find a weep when it's cold as it doesn't immediately turn to steam.

Edited July 4, 2022 by Quattrodave

[Tony Brooks]

10 hours ago, Megafugle said:

Apologies, to clarify. The water in the heat exchange is low/empty once we have been out for a drive, come back, waited for the engine to cool down and then checked the coolant levels. I dont open it when we are underway.

 

Ive also now noticed that the raw water exhaust is not spouting out any water. It was yesterday I promise! As such, most people have suggested I check the impeller. For my understanding, I presume the brass plate in the pictures below is the impeller? Ive looked at a few videos and they seem to suggest I simply remove the brass plating, pull out the fan part and then replace. This looks easy enough in the videos I have seen yet my impeller seems to be in a position where I cant possibly unscrew the screws due to proximity of the black metal plate.

 

Im not sure how to proceed.

 

 

1. Get spare end plate screws - they have  a habit of hiding in the bilge.

 

2. Turn off raw water inlet (Don't forget to turn it on before starting to test).

 

3. Remove the six screws and remove the end plate (I would not call it a front plate because on many engines it is at the back). Also remove the gasket.

 

4. Your impeller will be spline driven so although you can buy a special impeller puller I find two stubby Pozi or Philips screwdrivers as a pair of leavers work just as well. Note if any wings have disappeared - see below.

 

5. Unless the end plate has been reversed to  accommodate wear take the pump number off so you can order/ buy an impeller KIT. This should contain a new impeller, gasket, and special lubricant.

 

6. Do not make a gasket out of thick paper or card, it will be too thick and compromise pump capacity.

 

7. Lubricate the new impeller wings

 

8. Twisting the impeller in its normal direction of rotation start to work it into the pump body. It might jamb on the ends of the splines. If so put either a piece of wood flat against the exposed impeller face or use the flat of your hand, pushing the impeller into the housing (It won't go in). Flick the starter or turn the engine over in another way.

The impeller splines will align and the impeller go in.

 

9. If you do not have any of the special lubricant squirt washing up liquid between the impeller wings.

 

10. Lightly grease the new gasket and refit the end plate.

 

11. If any wings have gone missing check the inlet side of the  heat exchanger plus all the raw water hoses, bends and elbows for the broken wings & remove all debris found.

 

12. Start the engine and see how well it pumps water from the exhaust. If the pump is worn then it may need a small rev to start pumping at each restart.

 

 

[alan_fincher]

9 hours ago, Quattrodave said:

Yes, take the brass screws from the brass plate, remove the plate and rhe impeller should pull out.  Be careful when installing a new one all the lobes need to be pointing the correct way.

Yes, but......

 

Megafugle  says....

 

Quote

my impeller seems to be in a position where I cant possibly unscrew the screws due to proximity of the black metal plate

It's not entirely obvious to me what the "black metal plate" is, but it certainly makes it look like you can't get even a stubby screwdriver on some of the brass screws securing the cover plate of the Jabsco type pump.

Clearly at some time in it's life the pump cover has been removed.  Some of the screws show screwdriver damage, but far more obviously one has been replaced by a non-matching nut and bolt.  I suspect the thread in the pump body has probably been stripped on hat one....

[Megafugle]

Hi both,

 

Thanks again for your helpful comments. I think this might be starting to get a little above my level of expertise/ability. 

 

Checking for leaks and replacing an impeller, will this require a trip to a marina for a proper job, or is it something a marine engineer can do in situ? I appreciate this is a bit of an open ended question but having just purchased the boat and having had it transported here, im trying to reduce any unnecessary expense. Id rather get it properly done so I dont have to worry about in the future.

 

Thanks

 

 

[Tony Brooks]

The black metal plate looks like an engine mount to me. Although a decent right angle screwdriver will probably it those screws I think it would be easier to take the whole pump off from the two bolts holding its foot onto the engine

[Tracy D'arth]

Take the pump off its mountings, you may be able to leave the hoses on but they will be empty anyway so easier to have it off completely.

[Slim]

I would suggest that you get hex head setscrews as replacements together with a suitably small spanner. A pair of right angled, long nosed pliers would make getting the old impeller out easier. Looking at the photo you might well be able to grip the head of the obstructed screw with a small pair of alligator mole grips. Can't do any harm as if the attempt fails you've lost nothing. As for skills needed flexible joints are just as important.

Don't forget, It's a job that has to be done at least annually so buy a spare impellor.

 

If you do decide to tackle the job in situ I suggest you remove the screw at 4 o'clock first then the obstructed one. Leave the one at 12 o'clock till last and make sure the plate doesn't drop down into the bilge. 

All the above based on my experiences with my generator water pump which is every bit as inaccessible as yours😀

 

Edited July 6, 2022 by Slim

[Tony Brooks]

I have doubts there is sufficient clearance between the pump and what looks like an engine mount to get the impeller out.

[Slim]

2 hours ago, Tony Brooks said:

I have doubts there is sufficient clearance between the pump and what looks like an engine mount to get the impeller out.

 

2 hours ago, Tony Brooks said:

I have doubts there is sufficient clearance between the pump and what looks like an engine mount to get the impeller out.

You could well be right but it's worth a try,. (from the comfort of my armchair)

[Megafugle]

Thanks again everyone for your replies.

 

Im going to attempt to take the water pump off this weekend. Will keep you posted!

 

 

[Megafugle]

I cant claim credit for this, but I managed to get a friend of mine to remove the water pump and the brass plate today. It was attached to some kind of belt/pulley thing so well above my level of expertise (I also do not have many useful tools). 

 

Ive attached pictures of the inside below. To me, the impeller looks in pretty decent condition? There was a nice tight seal around the brass plate.

 

The good news is, after we fiddled and put everything back together, we are now seeing a good flow of water from the exhaust.

 

I am still going to monitor the coolant level in the heat exchange next time we take her out for a spin, but at the moment, I am hoping we are all ok.......

 

(If im wrong about the impeller looking ok, please tell me by the way!)

 

If the coolant levels in the heat exchange drop, I might be back.....

 

Thanks again for all the assistance.

 

 

 

 

[Tony Brooks]

The impeller looks fine to me as well. I note you have a Jabsco pump with a Johnson impeller fitted. Many Jabsco & Johnson parts are interchangeable, so it is exceptionally unlikely to be any sort of problem.

 

Those pumps are belt driven, very similar to the alternator. It is possible your belt was very slack and slipping so your friend adjusted it.

[Tracy D'arth]

At least you now know which impeller number to get as a spare. Good of them to put the numbers on the cover plate. I wish alternator makers would put the regulator number on them somewhere.

[Megafugle]

Ok. Im back, but not in a good way...!

 

Raw water system definitely working as it should. Water flowing very well from the exhaust. Coolant levels in the heat exchange were appropriate. Took her out for a couple of hours. All went well. Left her for the night, checked coolant level in the heat exchange in the morning, and its empty again.

 

Something is definitely amiss. Earlier on in the thread it was mentioned that there may be a puncture in the heat exchange core/manifold which might cause a leak. Considering I can all but confirm the raw water system (and ive checked the sea cock, water pump, impeller, belts and oil levels) is working as intended, would this now be something I need to consider? Is there any way to test for this?

 

Thanks again.  

 

 

[Quattrodave]

If you have a mityvac you can pressurise the coolant system and monitor for a pressure drop... hopefully then track down the leak...

[Slim]

I can't imagine that you've not checked but have you looked at the engine water pump? A 'slim' possibility I know because the signs are normally fairly obvious.

[Tony Brooks]

1 hour ago, Slim said:

I can't imagine that you've not checked but have you looked at the engine water pump? A 'slim' possibility I know because the signs are normally fairly obvious.

 

 

That was advised many posts ago I think. It is a good call because in the initial stages of failure they can  decide to only leak when running, only leak when stationary, or only leak when they think they will.

 

The OP needs to very carefully look for water/antifreeze stains in a streak down the front of the engine starting from under the engine water pump.

 

The OP could buy, borrow or hire a vehicle pressure tester, as also  suggested a while ago, so he can pressurise the system when full and cold.