Leyland 4/98 engine is overheating - any suggestions??

Talk about technical issues here. Questions and answers!

Topic author
santiago
Posts: 5
Joined: Wed Nov 28, 2012 1:39 am
Real name: Mary Turner

Leyland 4/98 engine is overheating - any suggestions??

Post #1 by santiago » Wed Nov 28, 2012 2:16 pm

Hello - I am new to this forum - never knew such a world existed! But I found it through searching on google for solutions to our overheating engine problem.

My name is Mary, I live on an old steel motor sailer boat designed by Alan Buchanan and built in 1961. I live in the caribbean with my man, Francois (who being french is not so good at ferreting out information online as I am). We have restored this boat - will attach pictures if anyone is interested. We didn't have to touch the engine at all to begin with as previous owner seemed to have kept it fairly well. But recently it has started to overheat, after about half an hour at a mere 800 rpm it starts to climb past 80 degrees and on acceleration it goes well above that and we stop the engine and start relying on the sails.

Francois has recently adapted the cooling system so that there are two feeds of sea water - one to the engine and another to the gear box - in the set up before the water cooled the gearbox first and then the engine. As the incoming seawater is permanently warm to start (28 degrees), it was suggested that this might help, but hasn't.

There is another minor niggle with the engine - in that it vibrates like crazy between 1200-1400 rpm. We never take the engine much above 1500 rpm - just out of respect for the old dear.

Your suggestions would be most welcome ...


Jeremy Rowland
Moderator
Posts: 8667
Joined: Sun Aug 05, 2007 8:36 pm
Real name: Jeremy Rowland
Has thanked: 1867 times
Been thanked: 1688 times

Re: Leyland 4/98 engine is overheating - any suggestions??

Post #2 by Jeremy Rowland » Wed Nov 28, 2012 2:27 pm

Hi Mary and welcome to the forum :wave: I have no knowledge of marine engine cooling systems but you imply that the engine in question has a supply of sea water to cool it? My suggestion therefore would be to check the water flow through this cooling system as you may have a blockage somewhere through corrosion or otherwise.

As for your engine vibration I would have thought that would be more of a transmission problem and not an engine issue, a damaged propshaft for example. :think:

Just a couple of ideas to try and help.

Jeremy


Topic author
santiago
Posts: 5
Joined: Wed Nov 28, 2012 1:39 am
Real name: Mary Turner

Re: Leyland 4/98 engine is overheating - any suggestions??

Post #3 by santiago » Wed Nov 28, 2012 3:17 pm

Hi Jeremy - thanks for your welcome and suggestions.

The cooling system has just been verified with the heat exchangers cleaned out and although there was no evidence of any blockage, everything was altered to double up the water flow and so expand the amount of water cooling the system.

The prop shaft is another story and had to be rebuilt when the boat was taking on a bit too much water last year. So that is all good - and it's a big one - 2 inches. The way it is all set up, it can't be realigned. But as I said, this vibration is a minor niggle in comparison to the overheating engine.

I apologise in advance if my terminology is a bit off - I have a superficial knowledge of engines and have to translate from french to give the detail.


essexpete
Posts: 4059
Joined: Fri Jul 13, 2007 12:43 am
Real name: essexpete
Has thanked: 849 times
Been thanked: 680 times

Re: Leyland 4/98 engine is overheating - any suggestions??

Post #4 by essexpete » Wed Nov 28, 2012 9:37 pm

You mention heat exchangers so I take it there is a sealed part with engine coolant (similar to a road vehicle) and a raw water side that draws sea water to ciculate through the exchangers and out through the exhaust?

User avatar

FOWLER MAN
Posts: 2358
Joined: Wed Dec 09, 2009 11:28 pm
Real name: fred evans
Has thanked: 1295 times
Been thanked: 1111 times
Flag: Wales

Re: Leyland 4/98 engine is overheating - any suggestions??

Post #5 by FOWLER MAN » Wed Nov 28, 2012 11:45 pm

Hi,
Have you checked that the thermostat is opening :?:
You can check it if you remove it by placing it in boiling water, it should open at about 85 degrees C. Don't be tempted to run the engine without it.
Is the sea water pump / pump impeller OK :?:
I think your engine may well be fitted with timed ballance shafts. :think: :?: Miss-timing these would be a source of vibration. :think:
Fred


Topic author
santiago
Posts: 5
Joined: Wed Nov 28, 2012 1:39 am
Real name: Mary Turner

Re: Leyland 4/98 engine is overheating - any suggestions??

Post #6 by santiago » Wed Nov 28, 2012 11:55 pm

Hi essex pete ... Yes that is it. The sea water is drawn in through a seacock by the impeller in the seawater pump via a 1 inch flexible pipe. The pipe then splits into two with one lot of water cooling the gearbox oil via a Bowman heat exchanger and the other pipe of water cooling the engine cooling fluid via another Bowman heat exchanger. There is no radiator or fan on a marine adapted engine. After passing through these heat exchangers the seawater is returned to the sea via the exhaust pipe.

Hope this makes sense ...

Hi Fowler Man

Thermostat is a good question - this was checked and didn't seem to be very movable - so Francois took it out. You say that an engine shouldn't be run without it, but as the water here is always around 28 degrees C and above and the air temp still higher, Francois who has removed thermostats on cars when he lived in hot climates, did the same on the leyland a few days ago. Is this a bad idea then??

Sea water pump and impeller are ok - new impeller fitted.

I am not sure what timed balance shafts are - so I can't explain that in French - will have to look up a translation and will get back to you on that one ...

Thanks for your advice ...

User avatar

modelman093
Posts: 646
Joined: Wed Jan 23, 2008 12:18 am
Real name: Angus Shapland
Has thanked: 8 times
Been thanked: 72 times
Flag: Great Britain

Re: Leyland 4/98 engine is overheating - any suggestions??

Post #7 by modelman093 » Thu Nov 29, 2012 12:38 am

The reason for not running without the thermostat is that in some applications it has a dual function. Closed it prevents the the water circulating through the radiator/heat exchanger but allows it to circulate around the head and block for a quick warm up. Open it allows circulation around the heat exchanger and positively shuts off the "short circuit" around the head and block. Remove the stat and instead of the full flow going to the heat exchanger some will take the short cut around the block and not get cooled. Think that they were referred to as shielded thermostats.
If the engine has balancer shafts they will be gear driven so unless there has been some fairly major work done they are unlikely to be out of synch.
Vibration - Suppose the obvious question to ask is does it vibrate both in and out of gear?! Also I expect that someone on the forum can say whether or not this engine has a crankshaft damper?
Not sure if it is applicable to a marine set up but prop shaft vibration on road vehicles could be checked/improved by putting a large worm drive clip (Jubilee clip) around the shaft and moving the heavy bit around bit at a time to see if it made things worse/improved things as the balance was altered. A really badly out of balance shaft might need two side by side.


essexpete
Posts: 4059
Joined: Fri Jul 13, 2007 12:43 am
Real name: essexpete
Has thanked: 849 times
Been thanked: 680 times

Re: Leyland 4/98 engine is overheating - any suggestions??

Post #8 by essexpete » Thu Nov 29, 2012 1:00 am

If the raw water side is OK then I would go with the suggestion of thermostat as that may be the cause although presumably it was taken out due to an overheating problem in the first place. Perhaps a head gasket check might be needed. Is it the original engine or has it been replaced with a similar unit? I am fairly certain that these engines could be supplied with a crankshaft balancer or without depending on the application. Is the engine bolted on proper flexible engine mounts or wood blocks? As modelman has asked does the vibration occur out of gear with no load or just when the prop is turning. Could the prop have hit anything since reinstallation?


essexpete
Posts: 4059
Joined: Fri Jul 13, 2007 12:43 am
Real name: essexpete
Has thanked: 849 times
Been thanked: 680 times

Re: Leyland 4/98 engine is overheating - any suggestions??

Post #9 by essexpete » Thu Nov 29, 2012 1:01 am

ps book us all in for a caribbean cruise if you get it sorted! :D

User avatar

FOWLER MAN
Posts: 2358
Joined: Wed Dec 09, 2009 11:28 pm
Real name: fred evans
Has thanked: 1295 times
Been thanked: 1111 times
Flag: Wales

Re: Leyland 4/98 engine is overheating - any suggestions??

Post #10 by FOWLER MAN » Thu Nov 29, 2012 1:05 am

Hello again,
The cooling water will take the least line of resistance, so without the restriction of the thermostat it will tend to bypass the heat exchanger and just circulate within the engine.
The advice was that if a deffective thermostat was removed and no replacement was available a gasket with a smaller hole or other restrictor should be fitted into the themostat housing to reduce the flow and direct sufficient of the coolant to the heat exchanger / radiator.
I have just checked, and if you go to the "download section" of this forum and click on JCB
you will find some information on the crank shaft ballancers in the JCB 3C 4/98 workshop manual. This is the same basic unit as yours, go to pages 57/58.
These ballancers were not fitted to all 4/98 engines.
Fred


Return to “Tech Talk”

Who is online

Users browsing this forum: No registered users and 8 guests