Low running temp and mayo in water header?

Wookey · Post by **Wookey** » 28 Mar 2005, 07:45

Hi guys,
Took my newly-fettled van (XUD9TE) for it's first long drive since getting the new turbo engine in on friday. Everything went very well except that the temp guage never moved above 77, which seems very low, and today I noticed there is a load of grey mayonnaise-type goo on the bottom of the water-header filler cap.
So - what might this mean?
For the temp I wonder if the sender unit in the new engine is soimply different from the one in the old engine (i.e. it is now not matched to the guage).
I know about mayo in the oil breather pipes, but the filler is fine and so is the oil. So this is just mayo in the water. It could just be that there was some crap in the engine as it was stored for best part of a year, and it has got washed out on first long run, and ended up emulsified at top of water. Or alternatively presumably I could have a serious problem...
I'll see how it goes next time we go somewhere, but any suggestionsof what to be looking for welcome.
(background: Expert van. 1.9D engine blew up on xmas day (dropped swirl chamber). Replaced with 1.9TD engine from xantia, turbo and manifolds and intercooler from synergie/806. Kept old gearbox so had to modify gearshift bracketry. Exhaust pipe is still old undersized one bodged to correct downpipe.)

oilyspanner · Post by **oilyspanner** » 28 Mar 2005, 18:34

Perhaps the thermostat is stuck open? The Mayo should go with a bit of motoring and some lubrication servicing.
Stewart

bxbodger · Post by **bxbodger** » 29 Mar 2005, 00:35

The only thing that will cause mayo in the coolant is oil mixing with it-it may be worth having a garage check for combustion gases in the coolant which will rule in or out a blown head gasket.
Regardibg the temp, the stat may be stuck or someone may have removed the thermostat to disguise an overheating problem- do you get good out of the heater?

fastandfurryous · Post by **fastandfurryous** » 29 Mar 2005, 05:38

you can get different temperature thermostats for the XUD series of engines, and some of them are quite low. I have a 79 degree one in my 405 at the moment, which does make it run a tad on the cool side, but I'd rather this than it overheat. (and it makes practically no difference to the fuel consumption on a diesel engine to run slightly cool)
Mayo in the coolant can indeed only be caused by oil contamination. I would say clean it out thouroughly, and see if it returns. If it does, that would suggest a head gasket failed between oil and water (the oil runs at a higher pressure than the water, and so you will only get oil in the water and not vice-versa) This is also exactly what I had with the 405, as I was getting blobs of oil in the top of the rad. You will only get mayonaise in the oil if there is failure to a cylinder too.
What mileage had the XUD9TE engine when you got it?

Wookey · Post by **Wookey** » 29 Mar 2005, 07:38

The engine has only done 56K miles and is reckonned to be in good fettle (head checked for both cracks and flatness). It did have one blued injector though, and another that wasn't atomising properly - fixing that made it run nicely.
I think the thermostat is OK because when I first ran it up to test it was some minutes before the top hose got warm, which is indicative of the thermostat waiting till the block was warm before opening. But still - it's easy to check (and see if it is a different temp to my other one. Should a TD thermostat be warmer/colder/the same as an NA thermostat? Do they have some marking on them to indicate the opening temp?
Yes the heater is working fine.
No-one thinks much of my 'wrong temp sender' theory then?

fastandfurryous · Post by **fastandfurryous** » 29 Mar 2005, 22:13

From "the head was checked for cracks and flatness" I'm guessing it wasn't skimmed? If not, it can be very difficult to get a decent seal on the aluminium with a new gasket, as even the most tiny bit of dirt/stuck old gasket/etc. can cause weepage. Personally I always have aluminium heads skimmed when they're off, as it's just not worth the risk of not doing it, especially when my local machinist can take off 0.5 thou, which is almost nothing, and could be done over 20 times before the head is scrap!
I believe the TD thermostat is a little cooler than the NA engine because the heat load in the oil is greater, due to the turbocharger and the piston cooling oil jets. This means that to have the oil run at the same temp as the NA engine, the Oil/Coolant intercooler (on the bottom of the oil filter) needs a slightly higher temperature gradient, and so the coolant needs to be slightly cooler.
First thing to do for sure it to give it a good clean out, and see if the Mayo returns.