Perkins 4108 Question

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Pete735

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After a long renovation, I started my Perkins 4108 last week for first time in 3 years. Initially I ran it with no cooling water just to check everything. I've run it today with a hose stuffed down pump inlet - I should mention boat is out of the water on a cradle. I've changed filter and oil and fitted a new fuel (lift) pump and fuel filter plus thermostat. As a matter of interest as it comes up as a discussion point periodically, previous owner always used easy start. I reconnected thermostart and with half throttle plus thermostart it starts after 2 or 3 revolutions, not bad for a 28 year old diesel and no sign of it having become addicted to easy start. Number 2 injector was weeping around the base so needs some work, but other than that all seemed very sound (touch wood)

Three questions;
1. what is the unit on top of heat exchanger (it's direct cooled) towards front of engine? About 2 inch diameter and 2 inch deep and screwed into thread in heat exchanger. Could it be some kind of pressure relief valve?
2. New thermostat is set at 74degrees C. Seems very low for an engine thermostat. Is it correct unit?
3. Could anyone with a similar set up tell me what running temp of engine they expect? After about 20 mins running, temp gauge was about 85 - 90 degrees C. At 1500rpm water pump also wanted more water as hose could not keep up with demand, lots of air bubbles showing in clear inlet hose - this surprised me. With sufficient water I would expect running temp to be slightly lower.

Thanks for any comments.
 
85 -90 sounds around right for an off load indirect cooled engine.

Bubbles from the water pump suggest there is (was) a leak on the suction side, or in the pump itself. Its not generally reckoned a good idea to run the hose straight onto the pump, as it does not allow the pump to work properly - either forcing too much water past it and possibly damaging the vanes, or flooding the engine, or starving it. The best way is to feed a large bucket with the hose, and arrange the pump inlet to draw from it. This also 'proves' the pump is working correctly.
 
I agree with Old harry about the bucket. I like a gently overflowing bucket in the cockpit (but you do have to be careful not to siphon the entire bucket full into the exhaust system when stopping the engine)

You say it is directly cooled but you refer to a heat exchanger. You mean it is indirectly cooled?

The 74° thermostat would probably be correct for a salt water cooled engine but one might expect to see one rated at a higher temperature for fresh water cooling.

Actually the Workshop manual says
Opening temperature 79.5 - 83.5C
Fully open 93.5 - 96C

Your running temperature does sound reasonable but with a better supply of cooling water it may tend to run cooler.

Re this "addiction" to Easy Start. They don't become addicted it is just that people don't fix whats wrong, they just keep on using the Easy Start. It can be bad news for diesels as you have no control over the time of the ignition, with petrol engines the Easy Start does not ignite until the spark ignites it at the correct time. It can also be dangerous with engines fitted with preheaters in the inlet manifold
 
VicS 'You say it is directly cooled but you refer to a heat exchanger. You mean it is indirectly cooled?'

Sorry, I explained this poorly. It is cooled by seawater and has an exhaust manifold that has water injection. The fitting I want to know about sits on top of this manifold towards the front of the engine. Is it some type of pressure relief valve?
 
[ QUOTE ]
It is cooled by seawater

[/ QUOTE ] Ok in which case 85 to 90C is too hot and 74C may well be the correct thermostat. The workshop manual I linked to does not cater for seawater cooled engines or even marinised engines for that matter. Sea water cooled engines have to be run at lower temperatures than fresh water cooled ones otherwise corrosion and scaling rates would be excessive.

I cant help with the fitting on the manifold and I cant think why there would be a pressure relief valve on a system which is not pressurised. Can you post a photo then perhaps someone will recognise it.
 
The unit on top of the manifold is a by pass valve, inside is a ball and spring which lifts to allow cooling water to by-pass the block when the thermostat is closed, worth unscrewing the lid to check as these sometimes stick.

74 is the correct thermostat.

lost of use of Easy start can make the head pourus reducing the cold engine compression, so they can become addicted. if you have to use brake cleaner instead,same affect without the side affects.

otherwise i agree with comments above..
 
[ QUOTE ]
lost of use of Easy start can make the head pourus

[/ QUOTE ] An explanation of the mechanism by which that occurs would be interesting.
 
sorry i'm not a chemist, I just fix the problems. it was explained to me many years ago but i can't recall the exact process.
Perhaps someone else can enlighten us both?
 
[ QUOTE ]
Perhaps someone else can enlighten us both?

[/ QUOTE ] Cliff, comments, publishable ones!
 
Just opened HWMBO workshop manual for 4 series Perkins and it says :
Indirect cooled engine - Thermostat opens at 69C, fully open at 87C
Direct cooled engine - Thermostat opens at 52C, fully open at 66C
(Page 27 of Manual)

Page 88 of ame manual indicates that your system is a later one with pressure relief system to allow water to bypass closed thermostat. The engine is designed to run at approx. 60C to prevent build up of salt deposits in head and cooling channels. Older engines on direct cooling had a manual valve you could adjust to control temp.
Indirect or Heat Exchanger cooled engines are designed to operate at higher temps of 65 - 93C.
It would appear then that you may have a higher rated thermostat than Perkins reccomend.
 
[ QUOTE ]
Just opened HWMBO workshop manual for 4 series Perkins

[/ QUOTE ] It would be jolly useful to get scanned copy of that on-line somewhere. On Bluemoment perhaps alongside or instead of the existing one.
 
Ok, thanks Moody1. I thought 74 degrees was low!! I bought the thermostat from ASAP supplies, so first port of call will be them - bet I know what the answer will be though. Only problem I find with Perkins info is that you have to go to local agent who then contacts Sabre ( I think it is) who then contacts Perkins and lethargy takes over in my experience. At the temperatures you quote I may as well remove thermostat all together.

Any chance of a scanned copy of the manual you have?

I'll try and remove pressure relief valve - despite temperature I noted on gauge (which may not be particularly accurate) this relief valve did not open. As I do refrigeration work, measuring temperatures accurately is not a problem.

Thanks everyone for the comments.
 
[ QUOTE ]
There is one here

[/ QUOTE ] Looks like the same one as on Bluemoment.

Moody1 seems to have one that relates to the marine engine.
 
I was given an explanation recently that sounded plausible - from someone who repairs diesels for a living. The ether (I think it is) in easystart removes the oil on the cylinder walls, obviously in minute quantities, and over time there is excessive (compared to "normal" useage) bore wear. The compression decreases and there is poor starting as a result so more easystart is used, till it will only start on easystart.

Others may have a better explanation.
 
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