I thank you in advance to reading this, I know I am a women and yes this is about a Horsebox lorry a MAN 1999 horsebox which I am having huuuggeee problems with so please please bear with me boys, even though I have taken it to the garage 3 times.
I will say the quick story and sorry if it is long winded. Bought this lorry 1month ago, drove it home from Rochdale down to Abersoch, well rather it didn’t really make it, after being stuck on the M62 for 2hrs in solid traffic and crawling, managed to get on the M56 and gave her a good run, next thing STOP engine light came on and I noticed that the temp gage was right at the top. Called out assistance, they thoroughly checked her and could not understand what was really wrong, they ran her solid for 4hrs, reving the engine now and then, nothing, no water leaks or anything. Anyway on the way home following morning managed to drive 20mils and same thing happened, could water was flowing out of the small overflow pipe in the water tank but no where else. ANyway the garage has since, flushed the system out, put in a new thermostat and told me she was good to go, I only managed a 10mile trip and same thing happened again, water gage right to the top and engine stop light came on, when I saw it slowly going up I put heaters on full blast, but when the gage went up, the heating became stone cold like being in a fridge. The garage are at their wits end, head gasket is fine, oil nice and clean, we just don’t know what is going on, we live over 100miles from a commercial garage that I know of that deals with MAN, I wouldn’t even reach 10miles with her the way she is now so can’t get to the garage. My question is if there are any specialist MAN mechanic would you have any advice, bearing in mind what the garage has already done, I am at my wits end and very upset because paid £15000 for this horsebox newly converted, and we had only bought her 2hrs prior to her breaking down, the people refused to take her back as it was a private sale.
Any advice or help would be much appreciated
Have you tried contacting a franchised MAN dealer? They don’t call them german bedfords for no reason but it should be fixable, they will have a half dozen mobile mechanics that can come out to you.
i woud suggest that simply leaving it running isnt putting enough stress on the engine to make it overheat. so, my opinion for what its worth. i aint no mechanic but i do however own landrovers so you may know that any landrover owner faces a crash course in mechanics or bankruptcy!!
i would suggest the water pump isnt functioning correctly, any belt or viscous coupling could be suspect if there is one there. also the radiator could also be partially blocked. only way to find out is to flow test it or replace it. flushing can cure it but once the ■■■■ has built up in there it can be tough to shift.
In short i think its a flow problem. if the headgasket and block/head are all pressure tested and fine it has to be water flow.
on the rover V8 petrol engines the liners used to slip and/or the heads crack. sometimes this was only evident when you had put pressure on the engine. some could tickover for eternity. ask the garage to do a sniff test. i suspect the original owner has looked for the issue, then decided one of these chemical sealers was in order and then bunged up the radiator. common thing on DIY mechanics.
plus, we all know how the horse world works!! theres some very dodgy dealers out there who have no qualms with selly really dodgy horses let alone horse boxes!!
good luck with it, hope it all gets sorted. theres nothing like being grounded this time of year when the season has just starrted!! 
Quote me if I’m wrong
Sounds as though you’ve got a none commercial garage undertaking repairs and think they are way out of there depth on this one… the way forward… so they’ve checked the hoses and flushed the system through as well as replacing the new thermostat…
Things that need to be checked in this order…
- Viscous fan …they need to check that its working by running the engine and get the engine temp up and see the fan physically kick in and work…could be something simple like an electrical connection… if its not then your next move is the intercooler…
You could always get the garage to ring the Man service centre and have a chat with them…ie what he’s done etc. etc
Thanks guys for your replies, going to show this to the garage so as they don’t think a woman has ideas!!! out of her depth, again thank you for taking the time to reply
last time this happened to me on a iveco it was a leaking waterpump. it was airlocking (hence the cold heater) and when it airlocked the pump was not working effectively and so it overheated…
MANs were prone to viscous fan failure & water pump problems . Some of the earlier viscous fans had a small locking plate on them which if I remember correctly was just a single bolt fixing , you slacken the bolt , slide the plate towards the middle of the fan into a recess/slot , and that locked the fan in permanently . It will be a bit noisy with it running all the time , but may help cure your problem
Suggest you repost this in the owner drivers forum, chances of a mechanic seeing it here is remote.
One simple suggestion, have you looked at the radiator itself, stick a torch behind, is it rammed with dead flies and general muck, might be an idea to blow not too high pressure water through the fins from back to front first.