Jump to content

Overheating problem


Recommended Posts

Had a great day at Devil's Pit today, but on the last lap of the course the engine started to get a little warm, and on the road home it started overheating, There wasnt much water in the expansion tank but I hadn't checked it that morning so it could have already been low. Eventually got home with the temp staying right at the very top of the white band nearly touching the black but not in the red. The heater got progressively colder and the engine appears to be running quite happily, she pulls well though i didn't push it hard.

This makes me think it's either the water pump gone or simply an airlock in the system, rather than anything like the head gasket. Anyone got any ideas or things I should be looking out for?

Link to comment
Share on other sites

Overheating after a play day is nearly always partially blocked radiators fins. The heat of the water in the rad bakes the mud into hard to remove clay. I wouldn't have thought it would affect your heater though, this is normally due to low water in the system. As Trevor says - there will be pounds of it in there.

Les. :)

Link to comment
Share on other sites

I'd fill her up and have a look for leaks! Radiators are prone for leaking (£100 if shop around).

If air is drawn into system when level low then the heaters do get less efficient (!), but you say "not much" water in expansion tank which I assume means there was some, so lack of coolant may not be the problem. Tdi's, I gather, are usually excellent at maintaining normal running temp and by the time the OME water temp guage tells you its getting hot, IT IS! You describe a water temp guage from a TD though?

Check the oil to see if the waters getting through headgasket (yukky milky), but this wouldn't be my first thought.....but I'm not an expert by any means!

Best bet, pour water in and see if it comes out again. If it doesnt may be the pump? However I bet there are better ways of diagnosing if the pump is at fault. :blink:

Edited - Oh yes and after reading the above (posted as I was writing) clogging happened to mine, which certainly reduced efficiency. Dont blart it out with high pressure jet washer though!! :(

Link to comment
Share on other sites

It was previously a 2.5TD and has had a 200TDi conversion at some stage, hence the original dash. :)

my 110 was a 2.5TD now 200Tdi, same dash/gauges, had a similar fault recently but it was the rads lower rear fins that had disintergrated, new rad cured the fault.

Link to comment
Share on other sites

How much coolant do you need to lose before there's a chance that the thermostat won't be submerged and reads incorrectly? I don't know if this applies to the 200TDi but it certainly does on a friend's Honda Legend. I'd expect some quite rapid changes with that though.

It first started getting hot after a revvy little climb (showing a fourtrak how it's done! :D ) but we'd already been up that slope half a dozen times in the afternoon. Even then it wasn't getting any hotter on the guage than a pushing it on the motorway, It shot up when we left the site 15 mins later and headed down the main road.

The thing that gets me is that the engine sounds and pulls fine, and you can't feel a lot of heat coming off it. Put it this way, the gauge is showing its very hot yet it doesnt seem to be giving off much heat to the air when you put your hand near it. I would expect her to feel and sound quite ropey. :blink:

Link to comment
Share on other sites

Didn't have your headlights on did you? Lots of Defenders have bad earths which cause ALL the gauges to read higher. I put another earth between the bulkhead and the engine and most of the problem has gone away. The slight increase in temp (and fuel level) I can live with.

Link to comment
Share on other sites

Headlights weren't on and it was a fairly dry run.

The engine is maintaining normal operating temp until you push it hard -lots of revs or high speed. Then it will increase to high temp but stay constant. Thoroughly strange, like the thermostat is faulty, Trouble is that still doesn't explain the heaters blowing cold air? Got myself really confused with this one now!

Does anyone have any photos of the thermostat housing on a 200tdi as the only photos in the Haynes are of the 300 and I want to be sure I'm dissembling the right part. Would the water in the expansion tank be getting hot even if the thermostat wasnt working and nothing was being directed through the rad?

Sorry for all the noob questions but I have very little free time especially in daylight hours so I want to try and get it right as quick as possible! :)

Link to comment
Share on other sites

Does anyone have any photos of the thermostat housing on a 200tdi

it's bolted on the front face of cylinder head directly above the water pump, to gain access to the thermostat, undo the 3 bolt heads IIRC 10mm hex head, and pull the upper casting off, it may need a few GENTLE taps with a soft mallet, Don't wack it hard as you will crack the alloy casting.

Link to comment
Share on other sites

Are there excessive bubbles in the header tank when you rev the engine, or a smell of diesel exhaust? Are the pipes rock-hard when you rev the engine gently? Lots of little bubbles will come from the normal action of the pump but big bubbles or excess gas could mean the head gasket's gone.

Hopefully it's just an instrumentation problem - I had nearly identical symptoms to you and fixed it all with a Racetech gauge and sender.

Link to comment
Share on other sites

A slight compression leak into the water jacket would cause these syptoms. As Turbo charger says - rock hard hoses, fine bubbles (or just a never-ending stream of them in the header tank without the level actually dropping). Overheating engine but cold heater. You can get a type of dye that you put in the cooling system that changes colour if there is exhaust gases or fuel present in the coolant.

Les. :)

Link to comment
Share on other sites

I have been smelling a bit of diesel exhaust on startup lately.. more so than normal. Haven't checked the hoses but will do afterwards. How hot should a 200tdi get? Because even after its "overheated" you can quite happily put your hand near the engine and it doesn't feel that warm,

I'm gonna go out and drain the coolant now so if the head gasket's had it I guess it'll be easy enough to see with oil in the coolant?

Link to comment
Share on other sites

Because even after its "overheated" you can quite happily put your hand near the engine and it doesn't feel that warm

Sounds a virtual certainty that it's the OEM temp sender/gauge, either check the temp with a thermometer/ simply get a decent replacement such as racetech. I had similar symptoms, although my injectors could have been partly responsible.

you could of course check earths, check the resistance on the sender — I think it should vary 300milliohms from hottest to coldest — although it's most probably the equipment itself.

Link to comment
Share on other sites

Didn't manage to drain the coolant but noticed it seemed gunky but not oily. perhaps just some dirt and it may be a bit old. Also, when squeezing the rad pipes, the thermostat rattled like it was opening and shutting with the pressure (engine off and cold) I assume this is a good thing cos it means its not stuck shut.

Am I checking the temp of the block itself by holding the thermometer up against it?

Not sure it could just be that though as it surely wouldn't affect the heater?

EDIT: The oil in the engine is low again so it must be going somewhere. Water doesn't seem to be dropping though it is a bit manky and milky. I'll do an oil change asap and check state of it. Need to get the rad out when I have more time as well, but it doesnt have a drain plug and I dont have a socket set long enough to get to the hose at the bottom.

Link to comment
Share on other sites

Put a lead light inside the motor so that light will shine through the rad fins. You will then be able to see from outside how badly the radiator core is blocked.

Flush the cooling system through and re-fill with fresh water (the level might drop once or possibly twice as any trapped air is expelled from the system over a day or two). A few additives such as Rad weld or bars leak will make the water milky - hence the need to flush the system. Oil mixed with water makes it milky, but when cold the gunky mess floats on the top and is looks, well, disgusting, coffee-coloured slime.

Water in the oil will have a similar effect, but unless there's loads of water in the sump, the oil will be a bit cloudy right up to a very smooth, cream-like coffee coloured liquid. Loss of compression into the water jacket is one way while the engine is running (the compression preventing water getting into the cylinder).

In quite extreme cases, the water will immediately pressurise as soon as the engine is started and if the cap is off the header tank - water will be forced out. A slight leak produces a steady stream of fine bubbles or a regular larger bubble being expelled without the water level dropping. The reason your engine overheats (and it does) is becuase the compression leak causes air pockets and thus restricts coolant flow. The radiator will feel cool to the touch or even at a normal temperature, but this is due to the mass of water in it and the fact that there may still be a small amount of flow through it. The heater packs up because the heater matrix is quite small and loses heat quickly, so restricted flow will dramatically effect it or air rises through the system and ends-up in the highest place - the heater matrix. You could have a cold heater, cold or normal temperature radiator, but the engine block/head will be 'cooking'. Sometimes you can hear the water boiling in the engine when you switch it off. If your engine has overheated, or it seems likely that it has, then you should replace the head gasket as soon as you can. It's virtually guaranteed that a head gasket will fail sooner or later if the engine has been cooked. Another thing to bear in mind is while the engine is off overnight or while you are at work, water may seep into one or more of the cylinders. If enough gets in there and you turn the key, you will hydro your own engine. :(

Les. :)

Edited by Les Henson
Link to comment
Share on other sites

Right, had the lot out. Engine oil is black, no signs of water etc. Coolant is milky/green with a tiny film of oil on top which could have washed off the chassis as it pee'd everywhere.

I'll refill everything and flush the system through when I get the time (but now I'm 3hrs late for work! lol). I took the thermostat out, but am confused about how you remove it from it's housing. Haynes suggests it just pulls out but mine seems to be stuck in solid. Not good?

So the head gasket probably isn't to blame as there oil/water havent mixed, but a loss of compression could be likely unless it's the thermostat playing up. The heater is probably airlocked so that's why thats not working. I think we're getting somewhere slowly now! Thanks again for all your help guys, I'll keep posting up what I find.

Link to comment
Share on other sites

Once the top is off of the thermostat housing there is nothing holding the valve assembly in place. Yes they do stick, and quite hard too. Lever it out with a screwdriver. If you suspect there is air trapped in the heater matrix just undo one of the pipe clips on the hoses that supply it when the engine is running and bleed the air out.

Les. :)

Link to comment
Share on other sites

If you open the heater controls to the hottest position as you fill up, it shouldn't really airlock anywhere. The Tdi is quite good in that respect, simply pour the coolant in and it fills up, give the top hose a few good squeezes as it fills that up and it should shift any air. But honestly I have never had a problem filling a Tdi with coolant.

Link to comment
Share on other sites

my 110 was a 2.5TD now 200Tdi, same dash/gauges, had a similar fault recently but it was the rads lower rear fins that had disintergrated, new rad cured the fault.

I still reckon it's the radiator not being able to disperse the heat quick enough,

have you carefully examined the fins as mentioned above?

what state are they in?

have changed the sender for a known good one?

Edited by western
Link to comment
Share on other sites

Rad looks fine but I may be being a numpty. After all she seems to only get hot when pushed past very gentle driving. I'll have it out and take it down my local garage for them to cast their eye over as what looks fine to me may actually be hiding something.

Havent changed the sender yet (assuming thats the little cylindrical object screwed into the thermostat housing?) so I'll probably do that when I have the rad out. Looks like a busy xmas :rolleyes:;)

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...

Important Information

We use cookies to ensure you get the best experience. By using our website you agree to our Cookie Policy